Class 9

Haryana State Board HBSE 9th Class Science Important Questions Chapter 9 Force and Laws of Motion Important Questions and Answers.

Haryana Board 9th Class Science Important Questions Chapter 9 Force and Laws of Motion

Very Short-Answer Type Questions

Question 1.
Define force.
Answer:
Force is that external factor that changes or tends to change the position of rest or speed and direction of moving object.

Question 2.
What is balanced force?
Answer:
When two or more forces acting on a body have zero resultant, then such forces are called balanced force.

Question 3.
What is unbalanced force ?
Answer:
When the resultant of two or more forces is not zero, such forces are called unbalanced force.

Question 4.
Which force works when a rubber ball is pressed between palms ?
Answer:
It is an example of a balanced force.

Question 5.
Which scientist has established the laws to control the motion of objects firstly?
Answer:
Sir Isaac Newton.

Question 6.
What is the angle of inclination?
Answer:
The angle made by an inclined plane with horizontal is called the angle of inclination.

Question 7.
Define frictional force.
Answer:
It is the opposing force that comes between the two surfaces in contact when a body moves or tends to move on another body.

Question 8.
Write the effect of frictional force.
Answer:
Frictional force reduces the motion of body.

Question 9.
Why the bicycle stops when we stop pedaling?
Answer:
The frictional force between the tyre of the bicycle and road reduces its motion and stops the bicycle.

Question 10.
Why powder is spread on the carom board in carom game?
Answer:
The powder is spread on the carom board to reduce the frictional force between carom board and coin.

Question 11.
What is the law of conservation of momentum?
Answer:
According to law of conservation of momentum, in absence of any external force, the total momentum of a system remains conserved.

Question 12.
Write Newton’s second law of motion?
Answer:
The rate of change of momentum of an object is proportional to the applied unbalanced force in the direction of force. ‘

Question 13.
What is meant by momentum?
Answer:
The momentum of an object is the product of mass and velocity. It is denoted by p.
or p = mv

Question 14.
What is SI unit of momentum?
Answer:
Kilogram metre per second (kg ms^-1).

Question 15.
Momentum is a scalar quantity or vector.
Answer:
Momentum is a vector quantity, because it has both magnitude and direction.

Question 16.
In which direction, the momentum works ?
Answer:
Momentum works in the direction of velocity.

Question 17.
What is the relation among force, mass and acceleration ?
Answer:
Force = Mass x Acceleration (F = ma)

Question 18.
What is the SI unit of force ?
Answer:
The SI unit of force is Newton.

Question 19.
Define one Newton force.
Answer:
One Newton force is that force which produces an acceleration of 1 ms^-2 in a body of mass 1 kg.

Question 20.
What is negligible action ?
Answer:
When a body affects the other by applying force, then we say that there is negligible action between first and second body.

Question 21.
How many types of inertia is ?
Answer:
There is two types of inertia:
(i) Inertia of rest
(ii) Inertia of motion.

Question 22.
Write the concept of force on the basis of momentum.
F = \(\frac{p_2-p_l}{t_2-t_l}\)

Question 23.
How much force will be required to produce an acceleration of 2mS“2 in 6 kg object ?
Answer:
Force (F) = Mass (m) x Acceleration (a) = 6 x 2 = 12 N

Question 24.
A person pushes a box of 40 kg with a force of 80 N. What will be the acceleration of box ?
Answer:
Acceleration (a) = = 2 ms^-2

Question 25.
Write Newton’s third law of motion.
Answer:
According to Newton’s third law of motion, “The action and reaction are always equal and in opposite direction.”

Question 26.
What is inertia ?
Answer:
That property of objects which opposes the change in its motion or state of rest is called inertia.

Question 27.
Is the existence of a single force is possible ?
Answer:
No, the existence of a single force is not possible. The force is always in pairs.

Question 28.
Which force offers us the motion in a desired direction ?
Answer:
The force which offers us the motion in a desired direction is the reaction of the earth opposite to the force applied by our body.

Question 29.
Are the action and reaction imposed on an object ?
Answer:
No, action and reaction (force) are imposed on two different objects.

Question 30.
Write the name of two forces which arise without the contact of two objects.
Answer:
(i) magnetic force
(ii) force of gravity.

Question 31.
How the fruit from tree falls towards the earth ?
Answer:
Due to force of gravity.

Question 32.
Why is it difficult to climb on a smooth pole ?
Answer:
Due to less reaction.

Question 33.
Why oil is used in machines ?
Answer:
To reduce the friction.

Question 34.
Why is it difficult to walk on sand ?
Answer:
Due to more friction between feet and sand.

Question 35.
Compare the frictional force between the surfaces of solids and liquids.
Answer:
The frictional force between the surfaces of liquids is much less than the frictional force between the surfaces of solids.

Question 36.
A small piece of stone and a truck are moving with same motion. On which, the larger force will be imposed to stop both of them ?
Answer:
The larger force will be required to stop the truck, because it will have large momentum.

Question 37.
By which force, we can walk on road without slipping.
Answer:
Due to frictional force, we can walk on road without slipping.

Question 38.
Why it becomes difficult to walk on a green mossy road in rainy season ?
Answer:
The frictional force becomes less on mossy road so it becomes difficult to walk on such a road.

Question 39.
Which Newton’s law of motion helps us in the measurement of force ?
Answer:
Newton’s second law of motion helps us in the measurement of force.

Question 40.
According to which Newton’s Law of motion, jet aeroplanes fly ?
Answer:
They fly according to Newton’s third law of motion.

Question 41.
Why the player runs before jump ?
Answer:
To increase the momentum so that the jump can be high.

Question 42.
Force is a scalar quantity or Vector.
Answer:
Force is a vector quantity.

Question 43.
What is the total momentum of rifle and bullet after firing from rifle ?
Answer:
Zero.

Question 44.
How much acceleration will be produced if 1 newton (N) force is applied on an object of 1 kg mass ?
Answer:
1 ms^-2

Short-Answer Type Questions

Question 1.
What is meant by force ? What can be the effect on object by applying force on that ?
Answer:
Force is that external factor which changes or tends to change the position of rest or speed and direction of moving object.
Effects:
Following are the effects on body, when force is applied :
(i) Speed of object can be changed due to which the object moves fast or slow.
(ii) The direction of motion of object can be changed and can move body in rest.
(iii) Shape of the object can be changed.

Question 2.
Give five examples of force in daily life.
Answer:
Examples of force in daily life are as follows :
(i) When a force is applied on a rubber ball, it elongated. It is due to force.
(ii)When a spring is stretched, its length increases due to muscular force.
(iii) The steam gives its energy to steam engine due to that the steam engine moves forward.
(iv) A rolling ball can be stopped by muscular force.
(v) Petrol produces mechanical force by its energy, due to that bus, car etc. moves.

Question 3.
What is inclinded plane ? What are its uses ?
Answer:
A smooth plane which makes an angle with horizontal plane is called inclinded plane, e.g. knife, axe, screw, hilly roads, stairs etc. A man lifting a heavy weight with the help of inclinded plane made of wooden piece is shown in below fi.

Uses of inclinded plane:
The uses of inclinded plane are as follows:
(i) A heavy weight can be lifted by small force by using inclinded plane.
(ii) Heavy weight is loaded or unloaded in trucks by using it.
(iii) Screw also works on the principle of inclinded plane.

Question 4.
Distinguish between balanced and unbalanced forces.
Answer:
The difference between balanced and unbalanced forces are as follows :
Balanced Force Unbalanced Force
1. When balanced forces act together on a body, their resultant is zero.
2. The balanced force can’t move a body which is in rest position.
3. This force cannot change the speed and direction of moving body.
4. This force always changes the size of body.

1. When unbalanced forces act together on a body, their resultant is not zero.
2. The unbalanced force can move a body which is in rest position.
3. This force can change the speed and direction of a moving body.
4. This force does not always change the size of body.

Question 5.
What is meant by inertia ? Clarify by example.
Answer:
The property of bodies which opposes the change in motion of body or state of rest is called inertia.

Experiment:
Set a coin on a stiff playing card covering an empty glass tumbler. Give the card a sharp horizontal flick with a finger. You will see the card moves ahead but the coin will fall in glass. When the card is shoot fast, then due to property of inertia, the coin tries to remain in rest position. In this way, when the card moves, the coin falls in glass.

Question 6.
What are the types of inertia ? Explain with example.
Answer:
Inertia is of two types:
1. Intertia of rest: The property of body by which the body resists its rest position until an external force is not applied on it.
Example: A book on table does not move due to inertia of rest.

2. Inertia of motion: The property of body by which it resists its state of motion, until an external force is not applied on it.
Example: A passenger sitting in a bus or cart falls forward when the moving bus or cart stops suddenly. In such situation, the lower portion of body of passenger comes in rest as the bus or cart stops, but the upper portion tries to remain in motion, due to this passenger falls forward. –

Question 7.
What happens when a wet cloth is jerked ? Clarify your explanation.
Answer:
When we jerk the wet cloth, the cloth displaced from its position to inertia and they detached from cloth and escape in environment. Thus, the cloth dries fast.

Question 8.
In javelin throw, if a player crosses the fixed line, he fouls, but the playes usually fail to stop on this line, why ?
Answer:
When in javelin throw competition, a player runs and reaches the fixed line, his whole body comes in motion. When he tries to stop his feet on fixed line, the upper portion remains in motion due to inertia of motion and the player crosses the fixed line and fouls.

Question 9.
Why the rider falls backward when the horse starts running suddenly?
Answer:
The rider falls backward when the horse starts running suddenly because due to suddenly running the horse, it comes in motion but the rider tries to remain in rest due to inertia of rest and falls backward.

Question 10.
Why the rider falls forward when a running horse stops suddenly?
Answer:
The rider falls forward when a running horse stops suddenly because the horse and rider are in motion when it is running and when horse
stops suddenly it comes in rest but the rider tries to remain in motion due to inertia of motion and falls forward.

Question 11.
Why are the tyres of vehicles made rough and treaded ?
Answer:
The movement of vehicles is due to the frictional force between road and tyres. If their tyres are smooth then the friction will be less betw een road and tyre, so that it will be difficult to control the vehicle. In order to control vehicles, the tyres are made rough and treaded so that the friction between tyre and road increases and grip of tyres with road will be firm.

Question 12.
Define and explain Newton’s first law of motion.
Answer:
Newton’s first law of motion:
An object continuous to be a state of rest or of uniform motion along a straight line unless acted upon by an unbalanced force. This law is also known as “Galileo’s Law of Inertia.” e.g. a ball rolling on floor can move far due to less friction. If the friction reduces to zero by any mean, the ball will move with initial velocity for a certain time.

Question 13.
Prove that Newton’s first law of motion can be called the law of inertia.
Answer:
According to Newton’s first law of motion, an object continuous to be a state of rest or of uniform motion along a straight line unless acted upon by an unbalanced force. In other word, all objects oppose the change in their state of motion. This tendency of the objects to oppose the change in their state of motion is called inertia. Thus, Newton’s first law of motion is also called the law of inertia.

Question 14.
Prove that the mass of a body is the measure of its inertia.
Answer:
The quantity of matter in a body is its mass. In this way, the mass is the measure of inertia of body. A body having large mass has large inertia.

Explanation:
If we kick a football it moves so far. but if we kick a stone, it will not move and our foot gets wound, because in comparison of football, stone has larger capacity to oppose the change in motion due to its larger mass. The mass of a body is the measure of its inertia.Thus, the inertia of a stone is more.

Question 15.
Define and explain Newton’s second law of motion with the help of this law, obtain equation of force.
Answer:
Newton’s second law of motion : The force applied on a body is proportional to the product of its mass and acceleration. If we kick a ball, it will move quickly because its acceleration becomes more. In this way, a cricketer stops a moving ball slowly, so that the change in motion of ball takes much time. He moves his hands in the direction of ball and the acceleration of ball becomes less in comparison of initial and less force is required to stop the ball. Let us consider a body has mass m and a force F produces an acceleration a in it. According to Newton’s second law of motion,
F ∝ m x a
or F = K ma ………..(i)
here, K , is a constant, whose value depends upon the units of mass, force and acceleration.
Let m = 1 kg, a = 1 m s^-2 and f = 1 N
then, putting the value of F, m and a in eQuestion (i)
1 = K x 1 x 1
or K = 1
F = 1 x ma
Force = Mass x Acceleration

Question 16.
Define and explain Newton’s third law of motion.
Answer:
Newton’s third law of motion:
To every action, there is an equal and opposite reaction and they act on two different bodies. Action and reaction are equal and in opposite direction.

For example:
(i) A ball presses the earth with a force, the earth pushes the ball upwards with same force.
(ii) When a person swims, he pushes the water backward, he moves forward, by this reaction.

Question 17.
Explain why does cricket player pulls his hands backward while catching a fast moving cricket ball ?
Answer:
The momentum of moving ball is more. When player catches the ball, he pulls his hands backward so that momentum of ball takes some time to become zero. In this way, momentum of ball, rate of change and the force applied on hand will become less and there is no hurt on hands.

Question 18.
Why larger force is required to stop a ship than car moving on road ?
Answer:
The frictional force between the tyres of car and road is more. Therefore the car stops quickly by applying lesser force. The frictional force between the surfaces of liquids is much less than the frictional force between the surfaces of solids. Due to this reason, the ship experiences less friction in water. Thus, larger force is required to stop a ship than car.

Question 19.
When there is negligible reaction between two bodies how the direction changes when two moving objects strike? Clarify with figure.
Answer:
When there is negligible reaction between two bodies, one body affects the other by force. The collision between two marbles is an example of negligible reaction. In figure two marbles are shown moving towards each-other. The direction of their motion is shown by arrow. It is clear from figure that the direction of marble changes after collision. Two forces act in this action. One is that which has accelerated one marble and second is that which has accelerated the other marble.

Question 20.
What is meant by action and reaction ? What is the relation between them ? In which law of motion, these are described ?
Answer:
If a body applies some force on other, then it is the active force on other body. In response, the force which second body applied on first is the reactive force on first body. The relation between action and reaction : The force of action and reaction are equal and in opposite directions. An important fact is that the force of action and reaction always act on different bodies. These are described in third law of motion.

Question 21.
Give some examples of Newton’s third law of motion in daily life.
Answer:
Following are the examples of Newton’s third law of motion :
(i) The bullet moves forward when trigger is pressed and due to reaction force, the gun recoils backward.
(ii) The person pushes the water backward while swimming and moves forward due to tne reaction or
water.
(iii) When a person jumps from boat at river-shore, the boat displaced far from shore due to reaction of water on that.
(iv) We press the earth backward while walking and
due to force of reaction the earth pushes our feet forward and we move. .
(v) The ores push the water backward and due to reaction, the boat move forward.
(vi) When a player jumps up, he pushes the surface of earth downward, so that he gets reaction.

Question 22.
Why the boat moves in opposite direction when a person jumps to shore from the boat ? Explain.
Answer:
A person applies force in upward to get the necessary motion at the time of jumping from boat. His reaction is on boat, which according to Newton’s third law of motion is in opposite direction. As a result of this, the boat move far on opposite direction.

Question 23.
Explain in brief, the relation between Newton’s first and second law of motion.
Answer:
The Newton’s first law of motion is the part of second law. It can be clarify on the basis of following fact:
According to second law of motion,
F = m a
if F = 0, then
m a = 0 m = 0,
a = 0
But mass, m cannot be zero, because it is a constant quantity. So, if acceleration a is zero, the change in velocity will also be zero. Therefore, there is no change in the position of body. If it is in rest, it will remain in rest, and if it is in motion, it will remain in motion unless external force is not applied. This is the statement of Newton’s first law of motion. Thus Netwon’s first law of motion is the part of second law.

Question 24.
What is the reason that a fast moving bullet makes a round hole in glass but on throwing the stone, the glass damages ?
Answer:
The size of bullet is small and that of stone is big so that the glass does not move when bullet is striked, only that part move where the bullet is striked and makes a hole, but there is no hole when stone is striked because whole glass moves and damaged.

Numerical Questions

Question 1.
Speed-time graph of a moving coin on table is shown in fig. . The weight of coin is 10 g.
How much force the table exerts to stop the coin?
Solution:
Here,
Initial velocity (u) = 24 ms^-1
Final velocity (v) = 0 ms^-1
Time (r) = 8 sec
Mass (m) = 10g = \(\frac {10}{1000}\) kg

We know that,
Acceleration (a) = \(\frac{v-u}{t}=\frac{0-24}{8}\) = \(\frac {-24}{8}\) = -3 ms^-2
∴ Force(F) = m.a
\(\left(\frac{10}{1000} \times-3\right)\) N
= – 0.03 N
(- ve sign shows that force decreases the motion.)

Question 2.
A cricket ball of mass 70g is moving with a velocity of 0.5 ms^-1. A cricket player stops it in 0.5 s. Calculate the force applied by the player to stop
the ball.
Solution:
Mass of the ball (m) 70g =\(\frac {70}{1000}\)= 0.07 kg
Initial velocity of ball (u) = 0.5 ms^-1
Final velocity of ball (v) = 0
The time taken to stop the ball, (t) = 0.5s
We know that, v = u + at
a = \(\frac{v-u}{t}=\frac{0-0.5}{0.5}=\frac{-0.5}{0.5}\) = -1 ms^-2
Thus, the force applied by the player to stop the ball
(F) = ma
= 0.07 x -1N = -0.07 N
(-ve sign shows that force is working against momentum.)

Question 3.
How much acceleration will be produced in the object ¡fa force of 200 N is applied on an object of 5 kg mass?
Solution: Here,
Mass(m) = 5kg
Force (F) = 200N
Acceleration (a) = ?
We know that, F = ma
a = \(\frac{F}{m}=\frac{200}{5}\) = 40 ms^-2

Question 4.
A constant force is working on an object of 5 kg mass for 2 seconds. It increases the velocity of object from 3ms1 to 7ms^-1. Calculate the value of applied force. Now, what will be the final velocity if the force works for 5 seconds on object?
Solution:
Here,
Mass of object (m) = 5 kg
Initial velocity of object (u) = 3 ms^-1
Final velocity of object (v) = 7 ms^-1
Time (t) = 2s
Acceleration (a) = ?
We know that.
a = \(\frac{v-u}{t}=\frac{7-3}{2}\)ms^-2 = \(\frac {4}{2}\) = 2 ms^-2
The force applied on object (F) = ma
= 5 x 2 = 10 N

In second stage,
Initial velocity of object (u) = 3 ms^-1
Final velocity of object (v) = ?
Time (t) = 5s
Acceleration (a) = 2 ms^-2
We know that,
v = u + a = 3 + 2 x 5 = 13 ms^-1

Question 5.
How much force is required to stop a car of mass 1000 kg and a loaded truck of mass 10,000 kg moving both with a velocity of 5ms in 2 seconds?
Solution:
Here.
Initial velocity of both (u) = 5ms
Final velocity of both (v) = O
time (t) = 2 s
Acceleration (a) = ?
We know that, v = u + at
a = \(\frac{v-u}{t}=\frac{0-5}{2}=\frac{-5}{2}\) = ms^-1

Mass of the car (m₁) = 1000 kg
Mass of the truck (m₂) = 10,000 kg
The necessary force to stop the car (F₁) = m₁ a
= 1000 x \(\frac {-5}{2}\) N
= – 2500 N
Thus, necessary force to stop the car = – 2500 N
(-ve sign shows that force is working against momentum.)
In same way, the necessary force to stop the truck (F₂) = m₂ a
= 10000 x \(\frac {-5}{2}\)N
= – 25000 N
Therefore, the necessary force required to stop the truck is more than that of car.

Question 6.
Which will require more force – to accelerate a body of mass 2 kg with a rate of 5 ms^-2 or to accelerate a both of mass 4kg with a rate of 2 m^-2?
Solution:
Here,
m₁ = 2kg
a₁ = 5 ms^-2
Force (F₁) = m₁a₁ = 2 x 5 = 10 N
m₂ = 4 kg
a₂ = 2 ms^-2
Force(F₂) = m₂a₂ = 4 x 2 = 8N
In this way F₁> F₂
∴ Large force will required to accelerate the object of 2 kg mass with a velocity of 5 ms^-2

Question 7.
A bullet of mass 20 g is horizontally fired with a velocity of 150 ms from a pistol of mass 2 kg. What is the recoil velocity of the pistol?
Solution:
Mass of bullet, m₁ = 20 g ( = 0.02 kg)
Mass of pistol. m₂ = 2 kg
The initial velocity of bullet (u₁) and pistol (u₂) is zero, respeciively.
That is u₁ = u₂ = 0
Final velocity of bullet, v₁ = + 150 ms^-1
The direction of bullet is taken + ve according to left to right system. Suppose, recoil velocity of pistol is v.
Total momentum of bullet and pistol before firing = (2 + 0.02) kg x o ms^-1
= 0 kg ms^-1
Total momentum after firing = 0.02 kg x (+ 150 ms^-1) + 2 kg x v ms^-1
= (3 + 2v)kg ms^-1
According to the law of conservation of momentum,
Total momentum after firing = Total momentum before firing
3 + 2v = 0
2v = -3
v = \(\frac {-3}{2}\)
v = -1.5 ms^-1
(-ve sign shows that the pistol recoils opposite to the direction of bullet i.e. right lo left.)

Question 8.
A coin is moving with a velocity of 24 cm s rolls with an acceleration of 3 cm² and stops in 8 s. Find the distance covered by the coin.
Solution:
Here,
Initial velocity (u) = 24 cm s
Final velocity (v) = 0
Acceleration (a) = – 3 cm s²
Time (t) = 8s
Distance (s) = ?
We know that, Distance (s) = ut + \(\frac {1}{2}\) at
= 24 x 8 + \(\frac {1}{2}\) x (-3) x (8)²
= 192 – 96
= 96 cm

Question 9.
In which the more force will require-to produce an acceleration of 5 ms in mass 10 g or to produce an acceleration of 2 ms2 in mass 20 g?
Solution:
In first stage, Mass (m) = 10 g = \(\frac {10}{1000}\) kg
Acceleration (a) = 5 ms^-2
The necessary force (F) = m x a
= \(\frac {10}{1000}\) x 5
= 0.05 N
In second stage, Mass (m) = 20 g = \(\frac {20}{1000}\) kg
Acceleration (a) = 2 ms^-2
The necessary force (F) = m x a = \(\frac {20}{1000}\) x 2 = 0.04N
Thus, larger force will be required to produce an acceleration of 5 ms2 in an object of mass 10 g. Answer:

Question 10.
A bullet of mass 20 g moving with a velocity of 16 ms^-1 enters ¡n a sand bag and comes in rest after 0.05 s. Find,
(a) depth of penetration ¡n sand
(b) the average resistive force applied by sand.
Solution:
Here,
(a) Initial velocity (u) = 16 ms^-1
Final velocity (v) = 0
Time (t) = 0.05 s
Distance (s) = ?
Average resistive force (F) = ?

We know that,
Acceleration (a) = \(\frac{v-u}{t}=\frac{0-16}{0.05}\) = 0.05
= \(\frac{v-u}{t}=\frac{0-16}{0.05}\)
= \(\frac{-16 \times 100}{5}\) = – 320 ms^-2
s = ut + \(\frac {1}{2}\) at²
= 16 x 0.05 + \(\frac {1}{2}\) x (-320) x (0.05)²
or s = 0.8 – 0.4 = 0.4m
(b) Mass (m) = 20 g = \(\frac {20}{1000}\) kg
Average resistive force (F) = m x a = \(\frac {20}{1000}\) x -320 = -6.4 N

Question 11.
How much will be the change in momentum of an object of mass 5kg, If Its speed:
(i) reduces from 20 ms^-1 to 0.20 ms^-1
(ii) Increases from 30 ms¹ to 40 ms^-1.
Solution:
Here,
Mass of the body (m) = 5kg
Initial velocity (u) = 20 ms¹
Final velocity (v) = 0.20 ms¹
Initial momentum (p₁) = m x u = 5 x 20 = 100 kg ms^-1
Final momentum (P₂) = m x v = 5 x 0.20 = 1.00 kg ms^-1
Thus, decrease in momentum = p₁ – p₂ = 100 – 1 = 99 kg ms^-1
Initial velocity (u) = 30 ms¹
Final velocity (v) = 40 ms¹
initial momentum (p₁) = m x v = 5 x 30 = 150 kg ms^-1
Final momentum (p₂) = m x v = 5 x 40 = 200 kg ms^-1
Thus, increase in momentum = 200 – 150 = 50 kg ms^-1

Question 12.
A driver accelerates a car In first stage with 1.8 ms^-2 and in second stage with 1.2 ms^-2 acceleration. Find the ratio of forces applied by engine in both stages.
Solution:
Let,
The mass of car = m kg
Acceleration in first stage = (a₁) = 1.8 ms^-2
∴Force in first stage (F₁) = m x a₁ = m x 1.8m = 1.8 m N
Acceleration in second stage (a₂) = 1.2 ms^-2
∴Force in first stage (F₂) = m x a₂ = m x 1.2 = 1.2m N
\(\frac{F_1}{F_2}=\frac{1.8 \mathrm{~m}}{1.2 \mathrm{~m}}=\frac{18}{12}=\frac{3}{2}\)
F₁:F₂ = 3:2

Question 13.
On applying a force for 1.2 s on an object, its speed increases from 1.8 ms^-1 to 4.2 ms^-1. The same force is applied for 2 s again. How much change in speed will be in 2s?
Solution:
Initial velocity in first stage (u) = 1.8 ms^-1
Final velocity (v) = 4.2 ms^-1
Time (t) = 1.2 s
According to formula, v = u + at
or u + at = v
1.8 + a x 1.2 = 4.2
or 1.2a = 4.2 – 1.8
or 1.2a = 2.4
or a = \(\frac {2.4}{1.2}\) = 2 ms^-1
∴ Acceleration = 2 ms^-2
initial velocity in second stage (u) = 4.2 ms
Time (t) = 2s
Acceleration (a) = 2 ms2
Final velocity (v) = u + at = 4.2 + 2 x 2 = v = 4.2 + 4 = v = 8.2 ms^-1
Thus, change in speed in 2s = 8.2 – 4.2 = 4 ms^-1

Do Yourself

(1) How much force will require to produce an acceleration of 2ms2 in an object of mass 12 kg? What
will be the acceleration, if force is doubled?
Answer:
24N, 4 ms^-2

(2)Aperson pushes a box of mass 50kg by a force of 80 N. What will be the acceleration of box ? What will be the acceleration of box if its mass is reduced to half?
Answer:
1.6 ms^-2, 3.2 ms^-2

(3) A motorcycle is moving with a velocity of 90 kmh1 and on applying brakes, stops in 5s. Calculate the force applied by brake on motorcycle, if its mass including driver is 200 kg.
Answer:
1000 N

(4) A rifle of mass 3 kg fires a bullet of mass 0.03 kg. The bullet leaves the barrel of the rifle at a velocity of 100 ms. ¡f the bullet takes 0.003 second to move through the barrel, calculate the force experienced by the rifle due to its recoil.
Answer:
1000 N

(5) Calculate that force which offers a velocity of 30 ms in lOs to a car, if the mass of car is 1500 kg.
Answer:
4500 N

(6) A car starts from rest and moves for 2 minutes with an uniform acceleration of 0.1 ms2. Calculate the distance covered by the car.
Answer:
720 m

(7) Calculate that force which will produce an acceleration of 0.40 ms^-2 in a toy car of mass 0.25 kg.
Answer:
0.1N

(8) An object is dropped froma height of 20 metres. 1f g = 10 ms^-2 then, calculate the velocity when it strikes to earth. Find the time taken to fall from that height.
Answer:
20 ms^-1, 2s

(9) The velocity-time graph of a ball of mass 20 g moving in straight line on a long table is giyen in figure. How much force will be table offer to ball to take it in rest?

Answer:
0.0004 N

(10) A bullet of mass 10 g leaves the barrel with a velocity of 300 ms1 in 0.0035 s. How much force was exerted by the rifle on bullet?
Answer:
857.14 NJ

(11) A car is moving with a speed of 108 kmh1 and takes 4s to stop after applying brakes. Calculate the force on car after applying brakes. Total mass of car including passengers, is 1000 kg.
Answer:
750 N

(12) A force of SN produces an acceleration of 10 ms^-2 in mass m1 and 20 ms^-2 in mass ms^-2. What will be the acceleration produced by this force, if both the masses are combined?
Answer:
6.67 ms^-2

(13)A resultant force of 15 N is applied on an object kept on a frictionless horizontal plane produces an acceleration of 5 ms^-2. Find the mass of object.
Answer:
3kg

(14) On applying a force of 5 N on mass in1, an acceleration of 8 ms2 is produced and by applying same force on mass ms^-2, produces an acceleration of 24 ms^-2 . How much acceleration will be produced by in combined mass by this force. 1f both masses becomes one by tieing?
Answer:
6 ms^-2

(15) Two hockey players of opposite teams, while trying to hit a hockey ball in the ground collide and immediately get entangled. One has a mass of 60 kg and is moving with a velocity of 5 ms^-2 while the other has a mass of 55 kg and is moving faster with a velocity of 6 ms towards the first player. In which direction and with what velocity will they move after they get entangled ? Assume the frictional force between the feet of the two players and the ground is negligible.
Answer:
Right to left and with velocity of 0.26 ms

Essay Type Questions

Question 1.
How Galileo proved that the object will move with a ceaseless speed if a balanced force is not applied on that object?
Answer:
On the basis of experiments written ahead, Galileo first of all told that the object will move with a ceaseless speed if a balanced force is not applied on that object. Galileo studied the motion of objects on a double inclined plane. He observed that velocity of a body increases when it rolls down the inclined plane and decreases when it climbs upon as shown in fig.

Thus, he concluded that if the body moves on smooth plane then its speed neither increases nor decreases but its speed will remain ceaseless.
Now, he imagine that if a ball is allowed to go down by touching a hollow semi-spherical surface, it will reach the same height to which it was dropped. He concluded on the basis of motion of bob pendulum because the bob of pendulum attains that height from where it started moving. Semi-spherical surface works the same which thread does in pendulum.

After that he told that the shape of pot is taken as showm in fig., then the ball or object reaches the same height in this situation also. Yet, it has to cover large distance to do so.

Now, if the slope on the other side of pot is decreased, the ball covers the more distance to reach that height. In this way he concluded that if the slope is decreasing to one side of pot, the ball will cover the large distance. If there is no slope the surface becomes plane the ball will cover infinite distance and move with constant velocity.

Question 2.
What is the momentum of body ? Establish a relation between the momentum and force of a moving body.
Answer:
Momentum: The momentum of body is the product of its mass (m) and velocity (v). It is denoted by ‘p’
Momentum = Mass x Velocity
or p = mv
We know that a body accelerates if some force is applied to it. According to Newton’s second law of motion, the acceleration produced in a body depends upon the force applied on that. If by applying a force, ‘F’ on a body of mass m, produces an acceleration of ‘a’ then according to second law of motion
F = ma
a = \(\frac {F}{m}\) ………….(1)
Suppose, Initial velocity of body = v₁ms^-1
After time (t) the final velocity = v₂ ms^-1
Then a = \(\frac{v_2-v_1}{t}\)
From eqs. (i) and (ii) is
\(\frac{F}{m}=\frac{v_2-v_1}{t}\)
F = \(\frac{m\left(v_2-v_1\right)}{t}\)
F = \(\frac{m v_2-m v_1}{t}\)
But mv₁ = p₁ (Initial momentum)
and mv₂ = P₂ (Final momentum)
F = \(\frac{p_2-p_1}{t}\)
F = rate of chance of momentum.
Thus, the force applied on a body is equal to the change in momentum in unit time.

Question 3.
What do you understand by conservation of momentum ? Prove the law of conservation of momentum in mathematical way.
Answer:
Conservation Law of Momentum : According to this law, the total momentum of a group of objects remains constant until it is not act upon by external force.
Activity: To prove this law, suppose two objects A and B of mass m1 and m2 are moving with velocities u₁ and u₂ respectively. Let both react with each other till time t. After action, their velocities become v₁ arid v₂as
shown in fig.
if any external force does not act, then the rate of change in momentum of object A is m₁ \(\frac{\left(v_1-u_1\right)}{t}\) In the same way the rate of change in momentum of object B is m₂ \(\frac{\left(v_2-u_2\right)}{t}\) If a force F₁ is exerted on A by B and F₂ on B by A, then according to Newton’s second law of motion,

F₁ = m₁\(\frac{\left(v_1-u_1\right)}{t}\) ………….(1)
and F₂ = m₂\(\frac{\left(v_2-u_2\right)}{t}\) ………….(2)
According to Newton’s third law of motion, F₁ and F₂ act equally and ¡n opposite direction.
F₁ = -F₂ ………….(3)
From eqs. (1), (2) and (3), is
m₁ = \(\frac{\left(v_1-u_1\right)}{t}\) = m₂
or m₁(v₁ – u₁) = m₂ (v₂ – u₂)
or m₁v₁ – m₂u₁ = m₂v₂ + m₂u₂
or m₁v₁ + m₂v₂ = m₁u₁ + m₂u₂
or m₁ u₁ + m₂u₂ = m₁v₁ + m₂v₂ ………(4)

Thus, total momentum before collision m₁u₁ + m₂ u₂ is equal to total momentum after collision m₂v₂ . This is the law of conservation of momentum.

Question 4.
What is meant by friction ? Prove that it is a boon as well as curse.
Answer:
Friction: The opposing force that comes into play when a body moves on another surface or through a fluid (liquid or gas) is called friction.
Friction as a boon: The friction is a necessary evil because nothing is possible without it, that is:
(i) We cannot move if there is no friction between road and feet.
(ii) The vehicles cannot move if there is no friction between road and tyres.
(iii) The nail can be insisted in wall only due to friction.
(iv) Only due to friction, the match stick burns.
(v) It is possible to write on blackboard due to friction between chalk and blackboard.
(vi) Due to friction, we can write on copy.
(vii) The vehicles can be stopped only by friction.
(viii) The belts related to electric motors can move on wheels due to friction.

Friction as a curse: Besides a necessary evil, friction is harmful to us as:
(i) Due to friction the parts of machine get bear and tear.
(ii) Due to friction, the efficiency of machines is not 100%.
(iii) More energy is spent due to friction.
(iv) Due to friction, our shoes tear.
(v) Due to friction, the tyres of vehicles reduces.

Question 5.
Write the methods of reducing friction. Explain any one out of them.
Answer:
Methods of Reducing Friction : Friction can he reduced by following methods:
(i) The frictional force can be reduced by planing the depresions on the surface of body
(ii) Oil or lubricant educes the friction between two surfaces. Due to this the oil is put in the part machines and the friction can be reduced.
(iii) The mixture of water and soap can minimise the friction between two surfaces.
(iv) The friction can be minimize by using ball-bearings.
(v) When we sprinkle powder on a carom board, the powder tills up the depressions and the coin
(vi) In order to reduce friction, special shape is given to vehicles.
(vii) By polishing two surfaces and by putting coaltar on roads, the friction can be reduced.

To reduce the friction by using ball-bearIng : Ball-bearings are used in machines to reduce friction. Small balls are there in ball-bearings which are kept between the sliding surfaces of machines. You will have seen them in the wheels of cycle. These reduces the friction which save energy and work.

Practical Work ‘ .

Activity I.
Two activities to show the effect of force which proves that the force can change the size of body.

Procedure:
(i) Take a spring and pull it towards outside by holding its two ends. You, will see the size of spring increase, which shows the force applied on spring by us. It proves that the force can change the size of body.
(ii) Take a spherical rubber ball and press it between your palms. You will see that on pressing, the size of ball becomes some long. It proves that the force can change the size of body.

Activity 2.
Perform on activity to show that a body starts moving only when the force applied by us is more than frictional force.

Procedure:
Take a box and tell to children to push it. You will see that the box does not move if they apply less force, because the frictional force between the lower surface of box and rough surface of floor balances the force applied to push and due to this the box does not move. The children push the box with large force, but box does not move. This is because of that the friction force is still balances the pushing force. If the children push the box with much more force, then pushing force will become more than frictional force. Here, the unbalanced force is working and the box is moving. It proves that if the force applied by us is more than frictional force, the body moves.

Activity 3.
Perform an activity to show the effect of action and reaction. .

Procedure:
(i) Take a big rubber balloon and inflate it fully.
(ii) Tie its neck using a thread. Also using adhesive tape, fix a straw on the surface of this balloon.
(iii) Pass a thread through the straw and hold one end of the thread in your hand or fix it on the wall.
(iv) Now remove the thread tied on the neck of balloon.
(v) Now the air escape from the mouth of the balloon and the straw and balloon will move in opposite direction which shows reaction.

Procedure 2:
(i) Take a test tube of good quality glass material and put a small amount of water in it.
(ii) Place a stop cork at the mouth of it. Now suspend the test tube horizontally by two strings.
(iii) Heat the test tube with a burner until water vaporises and the cork blows out.
(iv) We observe that the test tube recoils in the direction

Quick Review of the Chapter

1. When a force is applied on a body, its :
(A) motion can change
(B) size can change
(C) direction of motion can change
(D) all of the above
Answer:
(D) all of the above

2. If the resultant of all forces acting on a body is zero, then all forces acting on body is called :
(A) balanced force
(B) unbalanced force
(C) frictional force
(D) none of these
Answer:
(A) balanced force

3. Unit of force is:
(A) joule
(B) metre per second square
(C) Newton
(D) metre per second
Answer:
(C) Newton

4. If the resultant of all forces acting on a particle is not zero, then forces are called:
(A) balanced force
(B) unbalanced force
(C) frictional force
(D) none of these
Answer:
(B) unbalanced force

5 Which scientist has established the laws of controlling the motion of objects firstly ?
(A) Sir Isaac Newton
(B) C.V. Raman
(C) Rutherford
(D) Neils Bohr
Answer:
(A) Sir Isaac Newton

6. Newton’s laws of motion are:
(A) 2 ‘
(B) 3
(C) 4
(D) 5
Answer:
(B) 3

7. Newton first law of motions is called:
(A) Law of friction
(B) Law of conservation of momentum
(C) Law of inertia
(D) Law of gravity
Answer:
(C) Law of inertia

8. The rate of change of momentum of a body is proportional to the force applied and in the direction in which force is applied. This is Newton’s:
(A) first law
(B) second law
(C) third law
(D) fourth law
Answer:
(B) second law

9. The product of mass and velocity of an object is called:
(A) momentum
(B) inertia
(C) friction
(D) force
Answer:
(A) momentum

10. SI unit of momentum is:
(A) kg^-2
(B) kg ms^-1
(C) kg m
(D) kg mh^-1
Answer:
(B) kg ms

11. The relation among F, m and a is:
(A) F = \(\frac {m}{a}\)
(B) Fa = m
(C) F = ma
(D) none of these
Answer:
(C) F = ma

12. The force required to produce an acceleration of 1 mc2 in a body of mass 1 kg is:
(A) 1 Newton
(B) 2 Newton
(C) 3 Newton
(D) 4 Newton
Answer:
(A) I Newton

13. The force which acts without the contact of two objects is:
(A) magnetic force
(B) inertia
(C) friction
(D) all of the above
Answer:
(A) magnetic force

14. According to which force, the apple faits on earth from tree?
(A) force of gravity
(B) inertia
(C) force of magnet
(D) frictional force
Answer:
(A) force of gravity

15. It is difficult to walk on sand because the friction between feet and sand is:
(A) less
(B) more
(C) normal
(D) not there
Answer:
(B) more

16. A piece of stone and a truck is moving with same speed. In order to stop both, which one will require more force to stop?
(A) truck
(B) stone
(C) none on them
(D) both require equal.
Answer:
(A) truck ‘

17. Which of the following force move the object?
(A) Gravitational force
(B) Unbalanced force
(C) Balanced force
(D) Frictional force
Answer:
(B) Unbalanced force

18. Why the lubricant is used in machines?
(A) To increase friction
(B) To decrease friction
(C) To zero friction
(D) To clarity
Answer:
(B) To decrease friction

19. The dust detached from carpet when beaten with stick because of:
(A) inertia of rest
(B) motion of carpet
(C) motion of stick
(D) force
Answer:
(A) inertia of rest

20. If an external force ¡s working on a body, It accelerates in the dxrection of force. The acceleration produced is proportional to:
(A) applied force
(B) velocity
(C) mass
(D) inertia
Answer:
(A) applied force

21. If the mass of two objects A and B is 6 kg and 34 kg respectively, then:
(A) the inertia of object A is more than B
(B) the inertia of B is more than A
(C) inertia of A and B are same
(D) inertia of A and B are zero
Answer:
(B) the inertia of B is more than A

22. According to Newton’s third law of motion, the force related to action and reaction should apply on:
(A) one body
(B) same bodies
(C) always different bodies
(D) is not necessary to have equal result but their direction should be same
Answer:
(C) always different bodies

23. The explanation of falling forward when get down from bus can be done by:
(A) Newton ‘s first law of motion
(B) Newton ‘s second law of motion
(C) Newton’s third law of motion
(D) all of the above
Answer:
(A) Newton’s first law of motion

24. Launching of rocket ¡s based on the principle of:
(A) Newton’s first law of motion
(B) Newton’s second law of motion
(C) Newton’s third law of motion
(D) all of the above
Answer:
(C) Newton’s third law of motion

25. If the mass of an object m, velocity y, acceleration a, then the momentum (p) will be:
(A) p = mv
(B) p = \(\frac {m}{a}\)
(C) p = ma
(D) p = \(\frac {m}{a}\)
Answer:
(A) p = mv

26. Which one of the following has mo inertia?
(A) a rubber ball
(B) a piece of stone
(C) a cycle
(D) a train
Answer:
(D) a train

27. The branch of a tree sheds its leaves when it is shedding fastly:
(A) due to mass
(B) due to inertia
(C) due to weight
(D) due to acceleration
Answer:
(B) due to inertia

28. If an object of mass 30 kg has the momentum of 120 kg ms’, then its velocity will be:
(A) 4 ms^-1
(B) 8 ms^-1
(C) 2 ms^-1
(D) 1 ms^-1
Answer:
(A) 4 ms^-1

29. When a running bus stops suddenly, you falls forward and when starts running suddenly from rest you falls backward, It Is
(A) due to mass
(B) due to weight
(C) due to motion
(D) due to inertia
Answer:
(D) due to inertia

30. The mass of a cart is 1500 kg. If the cart is to bring in rest with negative acceleration (retardation) of 1.7 ms^-2, then the force between the cart and road will be
(A) 882.35 N
(B) 2550 N
(C) 1500N
(D) 2550 kgm
Answer:
(B) 2550 N

31. A bullet of mass 10 g moving in a straight line with a velocity of 150 ms^-1 strikes with a wooden piece and stops after 0.03 s. How far the bullet will penetrate the wood?
(A) 2.25 km
(B) 2.25 m
(C) 22.5m
(D) 15m
Answer:
(B) 2.25 m

32. A body of mass 1 kg moving in a straight line with a velocity of 10 ms^-1 strikes with a wooden piece of mass 5 kg which is in rest. After that both move in straight line together. The total momentum before collision will be
(A) 10 kg ms^-2
(B) 2 kg ms^-1
(C) 50kgms^-1
(D) 10kg ms^-1
Answer:
(D) 10kg ms^-1

Haryana State Board HBSE 9th Class Science Important Questions Chapter 8 Motion Important Questions and Answers.

Haryana Board 9th Class Science Important Questions Chapter 8 Motion

Very Short-Answer Type Questions

Question 1.
What do you mean by rest ?
Answer:
When a body does not change its position with respect to its surroundings, then the body is said to be at rest.

Question 2.
What is meant by motion ?
Answer:
When the position of the body continuously changes with respect to its surroundings, then the body is said to be in motion.

Question 3.
What is meant by relative motion ?
Answer:
The increase or decrease in distance between two moving bodies is known as relative motion.

Question 4.
How the motion of air can be measured ?
Answer:
The motion of air can be measured by its effect.

Question 5.
Passengers are sitting in a moving train. Tell, about which objects the passengers are in rest position and about which objects the passengers are in motion ?
Answer:
A passenger sitting in a moving train is in the state of rest in comparison of other passengers and the luggage kept in train. But the same person is in motion as compared to outsider trees and buildings.

Question 6.
Give one difference betw een the motion of living and non-living things.
Answer:
Living organisms move by themselves but external factor is required for the motion of non-living things.

Question 7.
What is distance ?
Answer:
The total path travelled by a body between initial and final points is called distance.

Question 8.
What is displacement?
Answer:
The shortest distance between the initial and final position of the body is called displacement.

Question 9.
What is the SI unit of distance and displacement ?
Answer:
The SI unit of distance and displacement is metre.

Question 10.
What is meant by reference point or origin point ?
Answer:
A fixed point with respect of which a body is at rest or in motion is known as reference point or origin point.

Question 11.
What those quantities are called, which require magnitude and direction both for their expression ?
Answer:
Those quantities which require magnitude and direction both for their expression are called vector quantities.

Question 12.
Which quantities are expressed by magnitude only ?
Answer:
Scalar quantities are expressed by magnitude only.

Question 13.
Write two examples each of vector and scalar quantities.
Answer:
Vector quantities – Velocity and displacement.
Scalar quantities – Distance and speed.

Question 14.
When an object covers equal distance in equal intervals of time, then what its speed is called ?
Answer:
When an object covers equal distance in equal intervals of time, its speed is known as uniform speed.

Question 15.
Give two examples of uniform speed.
Answer:
(i) Motion of earth
(ii) Motion of pendulum of a watch.

Question 16.
When an object covers unequal distance in equal intervals of time, then what its speed is called ?
Answer:
When an object covers unequal distance in equal intervals of time, its speed is known as non¬uniform speed.

Question 17.
Write two examples of non-uniform speed.
Answer:
(1) Train starting from a station.
(2) Birds flying in the sky.

Question 18.
Write down the formula to find out the average speed of a moving object.
Answer:
The distance travelled by an object per unit time is known as average speed.

Question 19.
What is meant by velocity ?
Answer:
The distance covered by a moving body in one second in a certain direction is called velocity.

Question 20.
What is the unit of velocity ?
Answer:
The unit of velocity is metre per second (ms’1).

Question 21.
What is the relation among distance, speed and time ?
Answer:
Distance = Speed x Time

Question 22.
What will be the velocity of an athlete, if he takes 10 seconds to cover a distance of 100 metres ?
Answer:

Question 23.
What is meant by acceleration ?
Answer:
The rate of change of velocity of a moving body is called acceleration.
a = \(\frac {v – u}{t}\)

Question 24.
What is meant by retardation ?
Answer:
The rate of decrease in velocity in a certain direction is called retardation i.e. negative acceleration s called retardation.

Question 25.
What is SI unit of acceleration ?
Answer:
SI unit of acceleration is metre Der second sauare

Question 26.
Write example ot accelerated motion.
Answer:
A body moving in a circle with uniform speed is an example of accelerated motion.

Question 27.
Choose scalar and vector from following :
(i) Delhi is at a distance of 1450 km from Mumbai.
(ii) Delhi is at a distance of 1450 km in north from Mumbai.
Answer:
(i) It is an example of scalar quantity.
(ii) It is an example of vector quantity.

Question 28.
When, a body is said to be moving with uniform acceleration ?
Answer:
If there is equal change in velocity in equal intervals of time, then the body is said to be moving with uniform acceleration.

Question 29.
Define uniform circular motion.
Answer:
When a body moves in a circular path with uniform speed, its motion is known as uniform circular motion.

Question 30.
Which type of motion is shown, if the speed-time graph is a straight line ?
Answer:
It shows uniformly accelerated motion.

Question 31.
What will be the acceleration of the body, if the speed-time graph is parallel to time axis ?
Answer:
The speed of the body will uniform, therefore acceleration will be zero.

Question 32.
What shows the slope of speed-time graph of an object ?
Answer:
Acceleration of the object.

Question 33.
What the area under and between interval of speed-time graph of moving body shows ?
Answer:
The distance covered by the body in that time interval.

Question 34.
If the distance-time graph, parallel to time axis is a straight line, then average speed in different intervals will be equal or different.
Answer:
Equal.

Question 35.
If the distance-time graph of a body is a straight line, what you will say about the motion of the body ?
Answer:
The body will be in constant position.

Question 36.
If the distance-time graph of a body is a curve, then its average speed in different intervals will be different or uniform.
Answer:
The average speed will be different in different intervals.

Question 37.
If the speed of a moving body becomes 30 km/h from 0 in 2 hours, then what will be its acceleration?
Answer:
Acceleration =img= 15 kmh^-2

Question 38.
If a body is moving on circular track with uniform-speed, then which type of its motion will be ?
Answer:
Non-uniform and accelerate motion.

Question 39.
Speed of light is 3 x 10⁸ ms^-1. What will be its speed in kmh^-1 ?
Answer:
speed of light = 3 x 10⁸ms^-1 = \(\frac{3 \times 10^8 \times 3600}{1000}\)kmh^-1
= 1.08 x 10⁹kmh^-1

Question 40.
Rajdhani Express covers a distance of 1384 km in 17 hours. What will be its average speed?
Answer:

Question 41.
What will be the average speed of a car, if it covers a distance of 80 km in two hours ?
Answer:
Average speed = \(\frac {80}{2}\) = 40 kmh^-1

Question 42.
What is meant by circular motion ?
Answer:
When a body moves on circular track, its motion is known as circular motion.

Question 43.
Give two examples of circular motion.
Answer:
(1) The motion of the wheel of a vehicle.
(2) The motion of a stone tied on the end of a rope in plane circle.

Question 44.
What is meant by graph ?
Answer:
The figure representation of any information is called graph.

Question 45.
Which type of motion is shown by a freely falling object ?
Answer:
It shows a uniformly accelerated motion.

Question 46.
A stone is thrown in vertical direction, then its velocity is continuously decreasing. Why ?
Answer:
When a stone is thrown in vertical direction, its velocity continuously decreases because the acceleration due to gravity is always directed towards the centre of earth.

Question 47.
You have gone to school on 8 o’clock in morning and come back 2 o’clock in afternoon. What will be your displacement?
Answer:
Zero.

Question 48.
What will be the velocity of that object which is thrown vertically upward from the surface of earth and attains maximum height ?
Answer:
Zero.

Question 49.
What is the relation among s, u, a and t ?
Answer:
s = ut + \(\frac {1}{2}\) at².

Question 50.
What is the relation among v, u, a and t ?
Answer:
v = u + at

Question 51.
What is the relation among v, u, a and s ?
Answer:
v² – u² = 2as

Question 52.
What will be the speed of an athlete, when he completes a round in t seconds on a circular track of radius r ?
Answer:
Speed (v) = \(\frac {2πr}{t}\)

Question 53.
When there are clouds in the sky, the lightning and thundering happen in same time. First, you see the eightning After some time, the sound of thundering reaches to you. Can you tell, why it is so ?
Answer:
Because the velocity of light (3 x 10⁸ ms^-1) is much more than the velocity of sound (346 m/s).

Short Answer Type Questions

Question 1.
What is the difference between rest and motion ?
Answer:
When a body does not change its position with respect to its surroundings, it is called rest, e.g. a book lying on the table, a stone lying on the floor, etc. When the position of the body continuously changes with respect to its surroundings, it is called motion, e.g. a moving car, a running horse, etc.

Question 2.
What is meant by displacement ? When it is positive and negative ?
Answer:
The change in the position of body in a certain direction is called displacement.
The position of a body changes from x₁ to x₂, then the displacement (d) can be written as:
d = (x₂ – x₁)
The +ve and -ve signs of displacement shows the direction of change in position of body. If displacement is +ve, then body moves from left to right. If the displacement is -ve, then body moves from right to left. It is a vector quantity.

Question 3.
What is meant by speed ? Write its unit.
Answer:
Speed is the distance travelled by the body in unit time interval in any direction.

Suppose, a body covers a distance ‘s’ in time ‘ f, then its speed v = –
Unit of speed is metre per second (ms^-1). 1

Question 4.
What is meant by non-uniform motion ? Draw a graph for non-uniform motion.
Answer:
Motion of a body is said to be non-uniform, if it covers unequal distance in equal intervals of time, e.g. motion of a car on road, because its speed keeps on changing. Similarly, the motion of a train is an example of non-uniform motion, because train covers different distance in every second. Distance-time graph is shown to clear the motion of train. It is clear from the figure that speed changes with time and distance-time graph is not a straight line. It is an example of

Question 5.
How vector is shown ?
Answer:
Vector is represented by a straight line with an arrow head over it. The length of this line is proportional to the magnitude of vector and arrow head shows the direction, which is known as the ‘head’ of vector and other end is known as the ‘tail’ of vector. For example, a velocity of 30 ms^-1, 30° in south-west direction can be shown in the form of a line carrying arrow head, as shown in figure.

Question 6.
Two cars moving in opposite directions, cover an equal distance d in an hour. What will be displacement of each after an hour, if they are moving in north and south directions respectively ?
Answer:
Let O is the reference point of both cars.
The distance covered by car A from reference point O in hour in north direction = d
∴Displacement OA = d
The distance covered by car B from reference point O in hour in south direction = d
∴Displacement OB = d
Total displacement of both cars, AB = d + d = 2d

Question 7.
What is meant by graph ? What are its uses ?
Answer:
To draw the change in one physical quantity7 with respect to another physical quantity on two different axes is called graph.

Uses: The uses of graph are as follows:
(l) The relation among different quantities can be studied easily.
(2) The table of two or more than two quantities can be compared easily.
(3) It is more simple to explain quantity in graph than table.
(4) Graph represents data in less space in comparison to table which takes larger space to represent data.
(5) Quantity related to slope of graph can be found.

Question 8.
What is distance-time graph ? The distance covered by a bus in different time intervals is given in the table. Draw a distance-time graph with the help of it.

Answer:
A simple and successive method, which shows the different distances at different time of a moving body, is called distance-time graph. The distance covered by the bus in different time-intervals is shown in distance-time graph.

Question 9.
Draw distance-time graph for tw o bodies moving with uniform speed of 4 ms^-1 and 7 ms^-1 and compare it.
Answer:
We know that,
Distance = Speed x Time
(i) Distance-time graph for a body moving with uniform speed of 4 ms^-1.


(ii) Distance-time graph for a body moving with uniform speed of 7 ms^-1.

On drawing these values on graph paper, we see that distance-time graph of given body will be as the adjacent figure.

Comparison of Graphs:
The slope of the body moving with uniform speed of 7 ms^-1 will be more than that of the body moving with uniform speed of 4 ms^-1.

Question 10.
Distance-time graph for a body is shown in figure. Is it the graph of real situation ? Give reason.
Answer:
No, this is not the graph of real situation. Reasons are as follows:
(1) According to distance-time graph, the time taken to reach that point from where it started its journey is less than the time taken by it to complete that journey.
(2) Time (t) is such a quantity which is continuously increasing. This will be larger after t = 14.

Question 11.
Distance-time table of a moving car is as follows:

Draw distance-time graph for car on the graph paper. Answer: Distance-time graph for car:

Question 12.
The distances covered by Amitabh and Archna by their bicycles in different times:

Show both by distance-time graph.
Answer:
The distance-time graph for both is given below:

Question 13.
Draw velocity-time graph for a body moving with a constant velocity of 40 kmh^-1.
Answer:
To draw a velocity-time graph of a car moving with constant velocity’ of 40 kmh^-1. It means, car covers a distance of 40 km in an hour, 80 km in two hours, 120 km in 3 hours and so on, it can be seen from figure, that velocity-time graph is a straight line and parallel to time axis. It is true for all velocity-time graphs when motion is uniform.

Question 14.
How we can calculate the distance covered by a body in a given time by using velocity¬time graph ?
Answer:
Suppose the velocity-time graph of a car moving with speed of 40 kmh^-1 is as the given figure. Let us consider, we have to calculate the distance covered by the car between time and t₂. Draw perpendiculars from points t₁ and t₂ on time axis as shown in figure.

By this, we obtain a rectangle ABCD between graph and X-axis. In this rectangle side AD is equal to BC, which is equal to (t₂ -t₁), and side AB is equal to CD, which is similar to 40 kmh^-1. We know that, if a body moving with velocity (v) covers a distance (.s’) in time (?) then,
s = vt
∴ Distance covered by the car in time (t₂ – t₁) = [(40 kmh^-1) (t₂ – t₁)h]
= 40(t₂ – t₁) km
= Area of rectangle ABCD or the area under velocity-time graph shows the distance covered by the car. This is true for any velocity-time graph, whether velocity is uniform or non-uniform,

Question 15.
How velocity is calculated by straight-lined distance-time graph ? Explain.
Answer:
We can calculate the velocity of a car from its distance-time graph. In fig., think about the smaller part AB of distance-time graph of motion of car. We draw a straight-line from point A parallel to X-axis and from point B parallel to Y-axis to find the velocity of car. These two straight lines meet at a point C and make a AABC. Now, on graph, AC represents time-interval (t₂ – t₁), and BC is equal to distance (s₂ – s₁). It can be seen from the graph that when car move from point A to B, it covers a distance (s₂ – s₁) in time (t₂ – t₁)
Velocity of car = \(\frac{s_2-s_1}{t_2-t_1}\)

Question 16.
Show uniformly accelerated motion, non-uniformly accelerated motion and uniform retarded motion by graph.
Answer:
1. Uniformly Accelerated Motion: In uniformly-accelerated motion, speed-time graph is a straight a line.

2. Non-uniformly Accelerated Motion: In non-uniformly accelerated motion, speed-time graph is a

3. Uniformly Retarded Motion: In uniformly retardation, the acceleration is negative (-ve) and velocity time graph is a straight line.

Question 17.
Draw speed-time graph for a body, moving in a straight line. What the slope of this straight line show ?
Answer:
If there is equal change in the velocity of a body in equal intervals of time, then we can say that the body is moving with uniform acceleration. The speed-time graph for a body moving in a straight-line is shown in figure. If the speed of the body is v₁ at time t₁ and v₂ at time t₂, then
acceleration of the body, a = \(\frac{v_2-v_1}{t_2-t_1}\)

The time intervals (t₂ – t₁) and (t₄ -t₃) are equal as shown in figure, because the change in heights of speed are also equal. Therefore, this graph shows the motion of such a body, which is moving with uniform acceleration.
The speed-time graph of a body moving with uniform acceleration is a straight line. The acceleration of such body is the slope of this straight line.

Question 18.
How you will prove that the motion is relative ?
Answer:
In order to prove that the motion is relative, we can compare the passengers sitting in a moving bus or train with road or trees standing near the track, vehicle or persons, e.g. the passengers sitting inside the bus . or train are in rest as compared to the luggage lying inside, but are in motion as compared to outsided objects.

Question 19.
Write the difference between-
(i) vector and scalar.
(ii) uniform and non-uniform motion.
(iii) distance and displacement.
Answer:
The difference between vector and scalar:
Vector:
1. Those physical quantities which contains both direction and magnitude are known as vector quantities, e.g. velocity, displacement, force, etc.
2. Vector quantities are combined according to rule of triangle or parallelogram.
3. Vector quantities are represented by a straight line with an arrow head over it.

Scalar:
1. Those physical quantities which contain magnitude only is known as scalar quantities, e.g. distance, volume, mass, etc.
2. Scalar quantities can be combined algebraically.
3. There is no special method to represent scalar quantities.

(ii) The difference between uniform and non-uniform motion :
Uniform Motion:
When a body covers equal distance in equal intervals of time, its motion is called uniform motion, e.g. motion of earth, motion of pendulum of watch, the motion of moon around the earth.

Non-uniform Motion:
When a body covers unequal distance in equal intervals of time, its motion is called non¬uniform motion, e.g. motion of train starting from station, the motion of bus starting from bus stop, motion of cycle.

(iii) The difference between distance and displacement:

Distance:
1. The length of the path actually covered by the body is called distance.
2. It is a scalar quantity.
3. The distance between two points through different paths can be different.

Displacement:
1. The distance between the initial and final positions of the body is called displacement.
2. It is a vector quantity.
3. The value of the displacement between any two points is always same.

Question 20.
What is meant by uniform circular motion ? Justify your answer with example.
Answer:
When a body moves on circular track, it changes its direction at every point. Actually, circle is a polygon figure which has infinite sides. In figure any circular shaped track can be called a polygon of inner-sides. Therefore, a body moving in a circle with uniform speed is an example of accelerated motion. Although, there is no change in the speed of the body, but the direction of the motion of body is continuously changes. Example – Take a piece of thread and tie one stone on its one end and rotate it, it will be in a circular motion.

Numerical Questions

Question 1.
The distance between the home of a boy and school is 1.8 km, if he takes 5 minutes to reach school by cycle, then find his speed In metre/second.
Solution:
Distance (s) = 1.8 km = 1.8 x 1000 metres = 1800 metres
Time taken (t) = 5 minutes = 5 x 60 seconds = 300 seconds

= 6 ms^-1

Question 2.
A person takes 10 minutes to reach office from his home. If the office is at a distance of 3.6 km, then find the average speed of person.
Solution:
Total distance 3.6 km = 3.6 x 1000 m = 3600 metres
Total time = 10 minutes = l0 x 60seconds = 600 seconds
Total distance 3600 m

= 6 ms^-1

Question 3.
Trivendrum express moves from Guwahati at 23 : 30 hrs on Monday and after covering a distance of 3574 km, It reaches Trivendrum at 22 : 30 hrs on Thursday. Find out the average speed of
this train.
Solution:
The total distance covered by the train 3574 km
Total time between 23:30 hrs (Monday) to 22:30 hrs (Thursday) = 24 + 24 + 23 – 71h

= 50.34 kmh^-1

Question 4.
A car, starting from rest, acquire a velocity of 36 kmh’ in 10 seconds. Find out acceleration of the car.
Solution:
The car started from rest
∴ Initial velocity (u) = O
Final velocity (v) = 36 kmh^-1 = 36 x \(\frac {5}{18}\) = 10 ms^-1
Time (t) = 10 s
We know that. v = u + at
10 = 0 + a x 10
10 = 10 a
a = \(\frac {10}{10}\) = 1 ms^-1

Question 5.
A cycle moving with a velocity of 3 metre per second increase its motion with acceleration of 0.5 ms² . What will be Its velocity after 5 seconds and how much distance it will cover ¡n this time?
Solution:
Here, Initial velocity (u) = 3 ms
Acceleration (a) = 0.5 ms²
Time (t) = 5 s
Final velocity (v) = ?
Distance (s) = ?
We know that,
v = u + at = 3 + 0.5 x 5 = 3 + 2.5 = 5.5 ms^-1

(2) s = ut+ \(\frac {1}{2}\) at²
= 3 x 5 + \(\frac {1}{2}\) x 0.5 x 5 x 5
15 + 6.25 = 21.25 m

Question 6.
The uniform acceleration of a scooter is 4 ms2. How much distance will scooter cover after 10 seconds from its movement ? What will be its velocity after 10 s?
Solution:
Here,
Initial velocity of scooter (u) = 0
Acceleration (a) = 4 ms
Time (t) = 10 s
Distance (s) = ?
Final velocity (y) = ?
We know that
(1) s = ut + \(\frac {1}{2}\) at²
s = 0 x 10 + \(\frac {1}{2}\) x 4 x (10)²
s = 0 + \(\frac {1}{2}\) x 4 x 100 = 200m
(2) v = u + at = 0 + 4 x 10 = 40 ms^-1

Question 7.
A bicycle is travelling at a speed of 10 ms. The brakes are applied so as to produce a retardation of 0.5 ms2. Find, how far the bicycle travel before it is brought to rest?
Solution:
Initial velocity of bicycle (u) = 10 ms^-1
Final velocity (v) = 0
Retardation (a) = 0.5 ms^-2
We know that, v² – u² = 2as
(0)² – (10)² = 2(- 0.5) x s
– 100 = – 1s
s = 100 m

Question 8.
A car travels with uniform velocity 20 ms’ for 5 s. On applying brakes, the car comes to rest in 8s with uniform retardation. Draw, velocity-time graph. How far, the car will go after applying brakes?
Solution:
The velocity-time graph is shown in figure.
The distance covered by the car, after applying brakes
= area of ∆BDC = \(\frac {1}{2}\) x DC x DB
[ ∴ area of triangle = \(\frac {1}{2}\) x base x perpendicular]
= \(\frac {1}{2}\) x (13 – 5) x 20
= \(\frac {1}{2}\) x 8 x 20 = 80 m.

Question 9.
In a long running, the athletes have to move 4 rounds of running track The starting and end of race is at the same place. If the length of one round is 200 m then –
(a) how much distance is to be covered by athletes?
(b) what will be the total displacement when the athletes has completed the race?
(c) is the motion of athletes uniform or non-uniform?
(d) are the distance covered by the athletes and displacement equal, at the end of race?
Answer:
(a) The total distance to be covered by the athletes = 200 x 4 = 800 metres.
(b) Because the initial and final places of running track are at same place, therefore the total displacement of athletes = zero.
(c) The motion of athletes is non-uniform.
(a) The distance covered by the athletes at the end of race is not equal to displacement. Because –
Distance = 800 metres
Displacement = 0

Question 10.
Write the speed of following bodies in descending order –
(i) Bicycle running with a speed of 18 kmh^-1.
(ii) An athlete running with a speed of 7 ms^-1.
(iii)A car running with a speed of 2000 m min^-1
Solution:
We know that,
(i) 18 kmh^-1 = \(\frac {18000}{3600}\) ms^-1 = 5 ms^-1
(ii) 7 ms^-1
(iii) 2000 m min^-1 = \(\frac {2000}{60}\) ms^-1 = 33.33 ms^-1
∴ The descending order of speed of bodies is as follows:
(i) A car running with a speed of 2000 m min^-1.
(ii) An athlete running with a speed of 7 ms^-1.
(iii) A bicycle running with a speed of 18 kmh^-1.

Question 11.
A body moves with velocity of 2 ms^-1 for 5 seconds, in next 5 seconds, its velocity increases to 10 ms^-1 due to uniform acceleration. After that, its velocity decreases uniformly and comes in rest in 10 seconds, then
(a) draw velocity-time and distance-time graphs for the motion of the body.
(b) Show that portion in graph, where the motion is uniform and non-uniform.
(c) From graph, find the distance covered by the body after 2s and 12s and in the last lOs.
Answer:
(a) Velocity-time graph: The velocity of the body is 2 ms for first 5 seconds, which is marked
by AB in the graph. After that, it becomes 10 mst in another 5 seconds (between 5 and 10 s), which is marked
by BC in the graph. After that the body comes in rest in next 10 seconds, which is marked by CD in the graph.

(b) Distance-time graph: Because the speed of the body is not uniform. Therefore, distance-time graph is not a straight-line

From velocity-time graph, we find that the motion of the body is uniform in AB part, whereas the motion is non-uniform in BC and CD parts.
(c) (1)The distance covered by the body in 2s = 2 x 2 = 4 m.
(2) The distance covered by the body in 12 s = area of [OB’BA + BBC’C + CC’FF’]
Now, the area of rectangle OBBA = 2 x 5 = 10
Area of trapezium BB’C’C = \(\frac {1}{2}\) x (BB’ + CC’) x B’C
= \(\frac {1}{2}\) (2 + 10) x 5
= \(\frac {1}{2}\) x 12 x 5 = 30
Area of trapezium CC’FF’ = 4- (CC’ + FF’) x CF’
= \(\frac {1}{2}\) x (10 + 8) x 2 = \(\frac {1}{2}\) x 18 x 2 = 18
∴ The distance covered by the body in 12 sec 10 + 30 + 18 = 58 metres

(3) Distance covered in last lO seconds area of (trap. CC’ F’F + right-angle ∆FF’D
Now, area of trapezium CC’F’F = x (CC + FF’) x C’F’
= \(\frac {1}{2}\) x (10 + 8) x 2
= \(\frac {1}{2}\) x 18 x 2 = 18

Area of right-angle ∆FF’D = \(\frac {1}{2}\) x F’D x F’F = \(\frac {1}{2}\) x 8 x 8 = 32
∴ Distance covered in last 10 seconds = 18 + 32 = 50 metres.

Do Yourself

1. Rita takes 20 minutes to cover a distance of 3.2 km on a bicycle. Calculate her velocity in units of a kilometre minute and kilometre/hour.
Answer:
0.16 km/minute, 9.6 km/hour

2. Ahmed is driving his car with a velocity of 45 kmh^-1. How much distance will be covered in
(a) one minute and
(b) one second?
Answer:
(a) 750 metres
(b) 12.5 metres

3. Starting from rest, Saurabh paddles his bicycle to attain a velocity of 6 ms^-1 in 30 seconds. Then, he applies brakes after that the velocity of the bicycle comes down to 4 ms^-1 in next 5 seconds. Calculate the acceleration of the bicycle in both the cases.
Answer:
(a) 0.2 ms^-2
(b) -0.4 ms^-2

4. A train starting from rest attains a velocity of 108 kmh^-1 in 10 minutes. Calculate (I) acceleration (ii) distance covered by the train.
Answer:
(1) 0.5 ms²
(ii) 900 m

5. A train starting from rest attains a velocity of 72 kmh^-1 in 5 minutes. Assuming that the acceleration is uniform, find (j) acceleration of train and (ii) the distance travelled by the train while it attained this velocity.
Answer:
(i) ms^-2
(ii) 3 km

6. A car accelerates uniformly from 18 kmh^-1 to 36 kmh^-1 in 5 seconds. Calculate : (1) the acceleration and (ii) the distance covered by the car in that time.
Answer:
(i) 1 ms^-2
(ii) 37.5 m

7. The brakes applied to a car produces a negative acceleration of 6 ms2. if the car takes 2 seconds to stop after applying the brakes, calculate the distance it travels, during this time.
Answer:
12 m

8. A train covers a distance of first 30 km out of 60 km lengthy path with a uniform speed of 45 kmh^-1. By how much speed, the train will cover the remaining 30 km path so that its average speed will be 60 kmh^-1 ?
Answer:
90 kmh^-1

9. Choose right answer out of the following questions:
(a) How much distance will a car cover in 12 minutes moving with a speed of 35 kmh^-1’?
(i) 7 km
(ii) 35 km
(iii) 14 km
(iv) 28 km
Answer:
(i) 7 km

(b) If, the acceleration of the body moving with a speed of 20 ms^-1 in a straight line ¡s 4 ms^-2, then
how much speed of it will be after 2 seconds?
(1) 8 ms^-1
(ii) 12 ms^-1
(iii) 16 ms^-1
(iv) 28 ms^-1
Answer:
(iv) 28 mst

(C) The speed of a car becomes 50 kmh^-1 from 20 kmh^-1 in 10 seconds. The acceleration of this car is –
(i) 30 ms²
(ii) 3 ms²
(iii) 1 8 ms²
(iv) 0.83 ms²
Answer:
(iv) 0.83 mc²

10. A piece of wood slides down from rest on plane of 10m tong with an acceleration of 5 ms² . What will be the speed of piece of wood on reaching at the base of inclined plane?
Answer:
10 m /s

11.. A train is travelling at a speed of 90 kmh^-1 On applying brakes, a retardation of 0.5 mc² s produced. Find how far the train goes before it is brought to rest?
Answer:
625 m

12. A body covers a distance of 16 metres in 4 seconds and again covers a distance of 16 metres in 2 seconds. What will be the average speed of body?
Answer:
5.33 ms^-1

13. The odometer of a car represents 2000 km at the start of a trip and 2400 km at the end of the trip. If the trip took 8 hours then, calculate the average speed of the car in kmh’ and ms.
Answer:
50kmh^-1, 13.9 ms^-1

14. Usha swims in a 90 m long pool. She covers 180 m in one minute by swimming from one end to the other and back along the same straight path. Find the average speed and average velocity of Usha.
Answer:
Speed 3 ms^-1, Velocity = O ms^-1

15. Starting from a rest position, Rahul paddles his bicycle to attain a velocity of 6 ms1 in 30s. Then he applies brakes such that the velocity of bicycle comes down to 4 ms^-1 in the next 5s. Calculate the acceleration of the bicycle ¡n both the cases.
Answer:
0.2 m² 0.4 ms

Essay Type Question

Question 1
Prove the following equations:
(i) v = u + at²
(ii) s = ut + ut²
(iii) v² – u² = 2as
Solution:
(i) Let the initial velocity of the body = u
Time = t
Final velocity = v
Change in velocity = v – u
Rate of change in velocity (acceleration), a = \(\frac {v – u}{t}\)
at = v – u
at+u = v
v = u + at
Let the initial velocity of the body = u
Acceleration = a
and after time t, final velocity = v
1f after t sec, the distance is s, then distance (s) = average velocity x time
But, average velocity = \(\frac {v – u}{t}\)
∴Distance (s) = \(\frac {v – u}{t}\)
s = \(\frac {v – u}{2}\) x t
s = \(\frac {u + u + at}{2}\) x t [∴v = u + at]
s = \(\frac {2u + 2t}{2}\) x t
s = \(\left(\frac{2 u t+a t^2}{2}\right)=\frac{2 u t}{2}+\frac{a t^2}{2}\)
s = ut + \(\frac {1}{2}\) at²

(iii) We know that, v = u + at
Squaring both sides
(v)² = (u + at)²
v² = u² + a²t² + 2uat
v² – u² = a²t² + 2uaI
v²– u² = 2uat + a²t²

v²– u² = 2a(ut + \(\frac {1}{2}\) at²)
v²– u² = 2as

Practical Work

Experiment 1:
Describe one activity for the difference between distance and displacement.

Procedure:
Take a metre scale and a long rope. Walk from one corner of a basket-ball court to its opposite corner way and measure with the help of scale. This will be the distance covered by you, whereas you will get displacement by putting a straight-rope from one corner to another. Suppose ABCD is basket-ball court. Distance to go from A to C AB + BC, whereas displacement = AC.

Experiment 2:
Clarify with an activity that direction of motion changes at every point on circular track

Procedure:
Take a piece of thread and tie a small piece of stone at one of its ends, move the stone to describe a circular path with constant speed by holding the thread at the other end as shown in figure. Now, let the stone go by releasing with thread and measure the direction of stone.

By repeating the activity for a few times and releasing the stone at different positions of circular path, check whether the direction in which the stone moves remains the same or not If you carefully note, on being released the stone moves along a straight line tangential to the circular path. This is because once the stone is’ released, it continues to move along the direction it has been moving at that instant. This shows that the direction of mot ion changes at every point when the stone was moving along the circular path.

Quick Review of the Chapter

1. A train is moving. The passengers sitting inside it, are ¡n rest compared to :
(A) other passengers
(B) the luggage in the train
(C) outsider objects
(D) other passengers and luggage in train
Answer:
(D) other passengers and luggage ¡n train

2. A train is moving. The passengers sitting inside it, are in motion as compared to :
(A) other passengers
(B) the luggage in the train
(C) outsider buildings and trees
(D) other passengers and luggage in train
Answer:
(C) outsider buildings and trees

3. If any object changes its position continuously with respect to other object, then objett is in state of
(A) motion
(B) rest
(C) constant
(D) none of these
Answer:
(A) motion

4. If any object does not change its position with respect to its surroundings, then the object is in state of
(A) motion
(B) rest
(C) circular motion
(D) movement
Answer:
(B) rest

5. Which of the following moves by themselves?
(A) living things
(B) non-living things.
(C) both living and non-living things
(D) neither living nor non-living
Answer:
(A) living things

6. SI unit of distance is:
(A) km
(B) m
(C) cm
(D) mm
Answer:
(B) m

7. WhIch of the following is a scalar quantity?
(A) momentum
(B) velocity
(C) displacement
(D) distance
Answer:
(D) distance

8. Rate of change of velocity is known as:
(A) Speed
(B) Acceleration
(C) Momentum
(D) Force
Answer:
(B) Acceleration

9. When a body covers equal distance in equal intervals of time, it is said to be
(A) uniform speed
(B) non-uniform speed
(C) average speed
(D) accelerated motion
Answer:
(A) uniform speed

10. If acceleration is in the direction of velocity, then it is called:
(A) Negative acceleration
(B) zero acceleration
(C) Positive acceleration
(D) none of these
Answer:
(C) Positive acceleration

11. If acceleration is ¡n the opposite direction of velocity then it is called:
(A) Negative acceleration
(B) zero acceleration
(C) positive acceleration
(D) none of these
Answer:
(A) Negative acceleration

12. If an object moves ¡n a circular path with uniform speed, Its motion is called: [H.B.S.E. 2020]
(A) Uniform circular motion
(B) Non-uniform circular motion
(C) Uniform curved motion
(D) Non-uniform curved motion
Answer:
(A) Uniform circular motion

13. SI unit of speed Is: [H.B.S.E. March, 2019]
(A) ms^-2
(B) ms^-1
(C) kmh^-1
(D) kms^-1
Answer:
(B) ms^-1

14. The distance covered by a moving body in one second in a certain direction is called:
(A) velocity
(B) acceleration
(C) non-uniform speed
(D) uniform speed
Answer:
(A) velocity

15. What is the relation among distance, speed and time?
(A) distance x speed = time
(B) time x distance = speed
(C) distance speed x time
(D) none of these
Answer:
(C) distance = speed x time

16. What will be the velocity of athlete if he takes 10 s to cover a distance of 100m?
(A) 100 ms^-1
(B) 10ms^-1
(C) 10 ms^-2
(D) 10 ms^-2
Answer:
(B) 10 ms^-1

17. The rate of decrease In velocity in a certain direction is:
(A) +ve acceleration
(B) – ve acceleration
(C) +ve and – ve acceleration
(D) none of these
Answer:
(B) – ve acceleration

18. The downward slope in velocity-time graph shows:
(A) accelerated motion
(B) equal motion
(C) retarded motion
(D) none of these
Answer:
(C) retarded motion

19. Rajdhanl Express covers a distance of 1384 km in 17 hours. Its average speed will be:
(A) 81.4 ms^-1
(B) 81.4 kms^-1
(C) 81.4 mh^-1
(D) 81.4 kmh^-1
Answer:
(D) 81.4 kmlf1

20. If a car covers a distance of 80 km in 2 hours, then its average speed will be:
(A) 40 kmh^-1
(B) 40 kms^-1
(C) 40 ms^-1
(D) 40 mh^-1
Answer:
(A) 40 kmh^-1

21. Cheetah is the fastest land animal and can achieve a peak velocity of 100 kmh upto a distance less than 500 m. H the cheetah spots his prey at a distance of 100 m, what ¡s the minimum time it will take to get the prey, if the average velocity attained by ¡t ¡s 90 kmh?
(A) 3s
(B) 4s
(C) 5s
(D) 6s
Answer:
(B) 4 s

22. The distance-time graph of a body is parallel to X-axis. It shows that:
(A) body is moving with non-uniform motion
(B) body is moving with accelerated motion
(C) the body is at rest
(D) body is moving with uniform motion
Answer:
(C) the body is at rest

23. By converting the speed of 2 km/h in m/s, we will get:
(A) \(\frac {5}{36}\) m/s
(B) \(\frac {5}{18}\) m/s
(C) \(\frac {5}{9}\)m/s
(D) \(\frac {50}{9}\) m/s
Answer:
\(\frac {5}{9}\)m/s

24. What is the speed of light in:
(A) 3 x 10⁸ m/s
(B) 3 x 10⁷ m/s
(C) 3 x 10¹⁰
(D) 3 x 10⁵ m/S
Answer:
(A) 3 x 10⁸ m/s

25. Which of the following is right for displacement?
(A) it cannot be zero
(B) its magnitude is more than the distance covered by the body
(C) it can be zero
(D) none of these
Answer:
(C) it can be zero

26. The odometer of any vehicle shows
(A) speed
(B) velocity
(C) distance
(D) time
Answer:
(A) speed

27. When an object Is In uniform motion, its path seems to be
(A) straight line
(B) curve
(C) irregular
(D) circular
Answer:
(A) straight line

28. During an experiment, a wireless signal from a spaceship reached ground station in 5 seconds. What Is the distance of spaceship from the ground station?
(A) 9 x 10¹⁰kjn
(B) 9 x 10¹⁰m
(C) 9 x 10¹⁰cm
(D) 9 x 10¹⁰ mm
Answer:
(B) 9 x 10¹⁰ m

29. A train is moving with a speed of 90 kmh^-1, on applying brakes, it produces a retardation of 0.5 ms². How much distance will it cover before coming to rest?
(A) 62.5 m
(B) 6.25 m
(C) 625 m
(D) 625 km
Answer:
(C) 625 m

30. A trolley while going down an inclined plane has an acceleration of 0.2 ms^-2. What will be its velocity In 3s after the starts?
(A) 0.6 ms^-1
(B) 0.6 cms^-1
(C) 0.6 mms^-1
(D) 0.6 ms^-2
Answer:
(A) 0.6 ms^-1

31. A racing car has a uniform acceleration of 4 ms^-2. What distance will it cover in lOs after the
start from rest?
(A) 20m
(B) 200m
(C) 2000m
(D) 2m
Answer:
(B) 200 m

32. A stone is thrown in vertically upward direction with a velocity of S ms⁴. If the acceleration of the stone during its motion is 10 ms², in downward direction, what will be the height aftalned by the stone?
(A) 12.5m
(B) 125m
(C) 1.25m
(D) 0.125m
Answer:
(C) 1.25 m

33. A stone Is thrown in vertically upward direction with a velocity of 5 ms. If the acceleration of the stone during its motion is 10 mr2, in downward direction, how much time will ¡t take to reach at maximum height?
(A) 0.5s
(B) 5s
(C) 5 min
(D) 0.5 mm
Answer:
(A) 0.5 s

34. An artificial satellite Is moving in a circular orbit of radius of 42,250 km. What will be Its speed, if it takes 24 hours to revolve round the earth?
(A) 3.07 ms^-1
(B) 3.07 kmh^-1
(C) 3.07 kms^-1
(D) 3.07 cms^-1
Answer:
(C) 307 kms^-1

35. An athlete completes one round of a circular track of radius r in time t, then its speed will be:
(A) 2πrt
(B) \(\frac{2 \pi r}{t}\)
(C) \(\frac{t}{2 \pi r}\)
(D) none of these
Answer:
(B) \(\frac{2 \pi r}{t}\)

36. The proper relation among s, u, t land a is:
(A) s = \(\frac{2 \pi r}{t}\)
(B) s = u + at
(C) s = ut + \(\frac {1}{2}\) at²
(D) s = uv + at
Answer:
(C) s = ut + \(\frac {1}{2}\) at²

37. The relation among y, u, a and t ¡s:
(A) v = u – at
(B) v = u + at
(C) v² = u² – at
(D) v² = u² + at
Answer:
(B) v = u + at

38. The proper relation between y, u, a and s is:
(A) v²= u² – 2as
(B) v² = 2as – u²
(C) v² – u² = 2as
(D) v² + u² = as
Answer:
(C) v² – u² = 2as

Haryana State Board HBSE 9th Class Science Important Questions Chapter 7 Diversity in Living Organisms Important Questions and Answers.

Haryana Board 9th Class Science Important Questions Chapter 7 Diversity in Living Organisms

Very Short-Answer Type Questions

Question 1.
Define Taxonomy.
Answer:
Science of classification of organism is known as Taxonomy.

Question 2.
Who classified the animals on the basis of their habitat ?
Answer:
Greek thinker Aristotle classified the animals into different groups based upon their habitat and habits.

Question 3.
Which type of cells have nucleus, cell organelles and cell wall ?
Answer:
Eukaryotic cells.

Question 4.
In which cell have the capacity to produce multicellular organisms ?
Answer:
Cell with nucleus.

Question 5.
Name the principle due to which some cell group together to form a single organism.
Answer:
Division of labour.

Question 6.
What are plants ?
Answer:
The organisms which produce their own food (autotrophs) are called plants.

Question 7.
What are animals ?
Answer:
The organisms which are heterotrophic known as animals.

Question 8.
Who proposed the concept of evolution ?
Answer:
Charles Darwin in his book “The Origin of Species” in 1859.

Question 9.
Which are primitive or lower organisms ?
Answer:
The group of organisms still possess their ancient body on earth is known as primitive or lower organisms.

Question 10.
Which are advanced or higher organisms ?
Answer:
The group of organisms who have undergone lot of changes in their body are called advanced or higher organisms.

Question 11.
Name the biologists who classified kingdom of organisms into broad categories.
Answer:
Ernst Haeckel (1894), Robert Whittaker (1959) and Carl Woese (1977).

Question 12.
What is the name of classification proposed by Whittaker ?
Answer:
Five kingdoms.

Question 13.
Which biologist classified the Monera Kingdom into Archaebacteria and Eubacteria ?
Answer:
Carl Woese.

Question 14.
Define species.
Answer:
Species is a group of organisms that are capable of breeding amongst themselves so as to produce fertile young ones. It is the smallest unit of classification.

Question 15.
What is the basic unit of classification ?
Answer:
Species.

Question 16.
What is nomenclature ?
Answer:
The system of naming animals and plants is termed as nomenclature.

Question 17.
Who is the father of Taxonomy ?
Answer:
Carolus Linnaeus.

Question 18.
Why does system of writing scientific names called bionomial system ?
Answer:
In this system every organism is given two names. One name is generic and the other is specific name.

Question 19.
What is the scientific name of human ?
Answer:
Homo sapiens.

Question 20.
What is the International System of nomenclature?
Answer:
Binomial system.

Question 21.
What are different categories of classification ?
Answer:
Species, Genus, Family, Order, Class, Phylum and Kingdom.

Question 22.
What is Genus ?
Answer:
Similar species together form genus.

Question 23.
How many kinds of kingdoms classified the living world in ancient time ?
Answer:
Two kingdoms:
(i) Plantae
(ii) Animalia.

Question 24.
What is classification ?
Answer:
Arranging of organism into groups on the basis of similarities and dissimilarities, which also show their relationship is called classification.

Question 25.
Write an importance of classification.
Answer:
It makes the study of organisms easy.

Question 26.
Which scientist classified the all organisms of the world into plantae and animalia kingdoms?
Answer:
Carolus Linnaeus in 1758.

Question 27.
Who raised the third kingdom Protista?
Answer:
E.H. Haeckel in 1866.

Question 28.
Who proposed the fourth kingdom Monera and fifty kingdom Animalia ?
Answer:
Robert H. Whittaker in 1969.

Question 29.
Which is the living organisms grow in whole life ?
Answer:
Plants.

Question 30.
How many sub-kingdoms of plant kingdom divided by Eichler ?
Answer:
Two: Cryptogamae and Phanerogamae.

Question 31.
Fungi cannot prepare their own food. Why ?
Answer:
Because chlorophyll is not present in them.

Question 32.
How many types of Angiosperms ?
Answer:
They are of two types:
(i) Dicot plants
(ii) Monocot plants.

Question 33.
Give two examples of Gymnosperms.
Answer:
(i) Cycas
(ii) Pinus.

Question 34.
Give one difference between algae and fungi.
Answer:
Chlorophyll present in algae but absent in fungi.

Question 35.
What is lichen?
Answer:
The symbiotic relationship of algae with fungi is called lichen.

Question 36.
Which sub-group of Cryptogams related to fungi ?
Answer:
Thallophyta.

Question 37.
Give one example of bryophyta.
Answer:
Mosses.

Question 38.
Give one example of pteridophyta.
Answer:
Ferns.

Question 39.
What are cryptogams ?
Answer:
The plants which do not bear seeds and spores located in their sex orgAnswer:

Question 40.
What is phanerogams ?
Answer:
Those plants in which seeds are produced after reproduction are called phanerogams.

Question 41.
What is meant by gymnosperms ?
Answer:
The plants bear naked seeds are called gymnosperms.

Question 42.
What is meant by angiosperms ?
Answer:
The plants which bear seeds into the fruit is called angiosperms. .

Question 43.
What is the main feature of plantae ?
Answer:
They are autotrophic.

Question 44.
What is the main feature of Animalia ?
Answer:
Heterotrophic.

Question 45.
What is porifera ?
Answer:
Those animals which bear pores all over their body are known as porifera.

Question 46.
Give two examples of coelenterata.
Answer:
Hydra and sea anemone.

Question 47.
What is the name of flatworm ?
Answer:
Platyhelminthes.

Question 48.
What is the scientific name of tapeworm ?
Answer:
Taenia solium.

Question 49.
Which group of animals is heterotrophic ?
Answer:
Nematoda.

Question 50.
Give one example of annelida.
Answer:
Earthworm.

Short-Answer Type Questions

Question 1.
What is the science of Taxonomy and Classification ?
Answer:
Taxonomy:
The branch of biology in which organisms are classified is called Taxonomy. First of all D. Candolli used this word Taxonomy involves identification, nomenclature and classification of organisms.

Classification:
It arranges the organisms in groups or set on the basis of their relations. Animals and plants are ranked in different categories as follow: Phylum, Class, Order, Family, Genus and Species. First of all, Carolus Linnaeus (1707-1778) gave idea about it in his book ‘Systema Naturae Therefore, Carolus Linnaeus is known as father of Taxonomy.

Question 2.
Why is it necessary to classify the living organisms ? Explain in your own words.
Answer:
The number of organisms in the world is very large. These organisms possess some similarities and some dissimilarties. The structure of some organisms is simple and that of others is complex. The organisms differ in their structure, nature, life-cycle, nutrition, respiration and reproduction, etc. Therefore, so as to make their study convenient, their classification is essential. The organisms are classified on the basis of similarities and dissimilarities. The science of classifiation provides a base for other branches of biology.

Question 3.
What is classification ? Explain its importance.
Answer:
Grouping organisms on the basis of similarities, dissimilarities and their inter-relationships is called classification.

Importance:
(1) Classification gives a base to the other branches of biology.
(2) Classification makes the study of organisms easy and convenient.
(3) Classification provides a clear picture of organisms.
(4) It provides information about inter-relationship of organisms.
(5) The study of geography is completely based on classification of plants and animals.
(6) The classification of organisms also contributes to the development of knowledge in other subjects.
(7) The branches of biology like ecology, cell biology, etc. have developed due to science of classification.

Question 4.
What is binomial nomenclature ? Explain with an example.
Answer:
Binomial Nomenclature: This system of nomenclature was given by Carolus Linnaeus. According to this system 4200 species of animals were named and were published in a book ‘SystemaNaturae’in 1758. In this system each plant or animal is given two names : The first name indicates the genera and is known as generic name whereas the second name indicates the specific name or species. Linnaeus is known as the father of Taxonomy.

For Example:
the scientific name of mango is Mangifere indica, that of mustard is Brassica compestris and that of man is Homo sapiens.
In all these the first name is generic name and the second name is that of species. All these names are universal and are used throughout the world.

Question 5.
What are the salient features of two kingdom system of classification ? Why are bacteria and fungi classified along with plants ?
Answer:
The living organisms are generally classified into two kingdoms : kingdom Animalia and kingdom Plantae. In both these kingdoms the characteristic features of organisms are same but they still differ in some characters. The organisms belonging to kingdom animalia are motile and cannot prepare their own food as they lack chlorophyll.

On the other hand the organisms belonging to kingdom plantae are (generally) autotrophs and prepare their own food. They are non-motile and remain confined to the same place. Their cell wall is made up of cellulose. They contain chlorophyll and are green. Bacteria and fungi do not contain green coloured pigment called chlorophyll, so they are not autotrophs. These obtain food/nourishment from dead or living organisms.

Still they are classified along with plants (kingdom Plantae) because:
(1) Their cell wall is made up of cellulose.
(2) They obtain their food/nourishment in soluble form.

Question 6.
Describe the different categories of classification ?
Answer:
Categories of the classification are the following:

Question 7.
What is Cryptogamae and Phanerogamae ?
Answer:
1. Cryptogamae: They are lowest group of plants. They lack flowers and seeds plants. They have bidden reproductive sex orgAnswer: Asexual reproduction takes place by the formation of spores.

2. Phanerogamae: They are highest group of plants. They bear roots, stem, leaves, flower, fruit and ’ seeds. They reproduce sexually by means of seeds. The seed contains embryo and nourishing material.

Question 8.
How is cryptogamae classified ?
Answer:
They are flowerless plants. Reproductive organs are hidden in them. There is no external flower and seed consists in them. According to classification, by Lindale and Eichler, cryptogamae is divided into three main groups:
(i) Thallophyta; e.g. Ulothrix, Penicillium, Lichens, etc.
(ii) Bryophyta; e.g. Funaria, Marchantia, etc.
(iii) Pteridophyta; e.g. Ferns, Selaginella, etc.

Question 9.
What is the difference between monocot and dicot plants ?
Answer:
These are the following differences between monocot and dicot plants :
Monocots:
1. Seeds with one cotyledon.
2. The leaves of these plants have parallel veination.
3. The root system is fibrous in them.
4. There is no secondary growth.
5. Stem divided into nodes.
Example: Wheat, maize, bajra, etc.

Dicots:
1. Seeds with two cotyledons.
2. Veination in their leaves is reticulate with a network of veins.
3. Tap root system is present in them.
4. Secondary growth is present.
5. Stem is not divided into nodes.
Example: Mustard (sarson), pea, gram, etc.

Question 10.
What is animalia ? Write names of main phylum and important features of this group. Answer: Animalia : The multicellular organisms with lack cell wall are called animalia. Their important features are following :
(i) They are heterotrophic and autotropic.
(ii) Their growth is definite.
(iii) These are free moving organisms.

They can be classified in the following :
(i) Porifera
(ii) Coelenterata
(iii) Platyhelminthes
(iv) Nematoda
(v) Annelida
(vi) Arthropoda
(vii) Mollusca
(viii) Echinodermata
(ix) Protochordata
(x) Vertebrata

Question 11.
Describe main features of porifera phylum.
Answer:
The main features of porifera are following:
(i) They mostly occur in saline water although some are found in fresh water.
(ii) They are multicellular.
(iii) Cells in them are loosely held together. Thus, they have cellular level of organisation.
(iv) Skeleton is not found in them.
(v) The shape of their body is the vase or sac like.
(vi) They bear pores all over body, with simple large opening known as osculum on the top.
(vii) They possess a unique canal system.
(viii) They reproduce by asexual and sexual methods.
Example:
Sycon, Spongia, Euplectella, Spongilla, etc.

Question 12.
Describe main features of Coelenterata.
Answer:
The main features of Coelenterata is following:
(i) They are solitary or colonial.
(ii) Anus is absent in them.
(iii) They possess radial symmetry.
(iv) They possess coelenterata.
(v) They bear tentacles.
(vi) Their body have stinging cells called cnidoblasts.
(vii) Polyp and medusa come into their life cycle one by one.
(viii) Reproduction is usually asexual in polyp form and sexual in the medusa form Examples : Hydra, Obelia, Sea anemone, Coral, etc.

Question 13.
Describe the main features of platyhelminthes.
Answer:
Platyhelminthes are characterised by the following main features:
(i) They are often dorso ventrally flattened.
(ii) They are usually endoparasites.
(iii) They are triploblastic, the body develops from three layers.
(iv) Their body having bilateral symmetry.
(v) Sexual reproduction takes place in them.
(vi) Only one hole is present in the alimentary canal.
(vii’) They have dorsoventrally flat and leaf like or ribbon like body.
Examples:
Tapeworm, planaria, liver- fluke, etc.

Question 14.
Write the main features of the nematoda phylum.
Answer:
Following are the main features of nematoda phylum:
(i) They are endoparasites.
(ii) They possess bilateral symmetry.
(iii) Alimentary canal is complete.
(iv) They are pseudocoelomates. Body cavity is not a true coelom in them.
(v) They are unisexual.
(vi) They are triploblastic.
(vii) Body size is microscopic and other are several centimetres in length.
Examples: Ascaris, Roundworm, Pinworm, etc.

Question 15.
Write main features of annelida phylum.
Answer:
Annelida phylum are characterised by the following main features:
(i) They live in moist soil, in freshwater or saline water.
(ii) They have long and palpented body.
(iii) They are first animals with true body- cavity or coelom.
(iv) Nephridia is present in them for the purpose of excretion.
(v) Animals have bilateral symmetry.
(vi) They are unisexual or bisexual.
(vii) Some forms have unjointed locomotary appendages, the parapodia. Others have setae for locomotion.
Examples: Earthworm, leech, nereis, sea mouse, etc.

Question 16.
What are the main features of arthropoda ?
Answer:
Arthropoda is characterised by the following main features :
(i) They occur everywhere, on land, in soil, in fresh and saline water.
(ii) They are heterotrophic.
(iii) They possess jointed legs.
(iv) Their body is segmented and divided into three regions: head, thorax and abdomen.
(v) Interior part of the body forms the distinct head, which bears well-developed sense orgAnswer:
(vi) Their body is covered externally by a chitinous exoskeleton.
(vii) Circulatory system is of open type.
(viii) Haemocoel present in them.
(ix) Male and female reproductive organs are separate.
Examples: Cockroach, crab, scorpion, bee, butterfly, mosquito, etc.

Question 17.
Write features of hemichordata phylum.
Answer:
Features of hemichordata are the following :
(i) They are worm-like unsegmented organisms.
(ii) They are all marine animals.
(iii) They may be solitary or colonial.
(iv) Their body is divisible into proboscis, collar, and trunk.
(v) They are bilaterally symmetrical.
(vi) Respiration takes place by gill slits.
(vii) Sexes are mostly separate.
Examples: Balanoglossus, Cephalodiscus, etc.

Question 18.
Write major differences of non-chordata and chordata.
Answer:
Non-chordata and chordata have following differences :
Non-Chordates:
1. There is no tail behind the anus.
2. Haemogloblin plasma dissolved in their blood.
3. Heart, if present, is dorsal.
4. Nervous system is ventral and solid.
5. Pharynx gill slits are absent

Chordates:
1. Tail is present behind their anus.
2. Haemoglobin is present in their red blood cells.
3. Heart is ventral and in a pericardial cavity.
4. Nervous system is dorsal and hollow.
5. Pharynx gill slits are present.

Question 19.
Write important features of chordata phylum and classified this phylum. Answer: Important features of chordata phylum are the following :
(i) Presence of nerve chord and hollow nervous system.
(ii) They all have paired gill slits.
(iii) Solid, elastic notochord occurs in all chordata and in any stage of life.
(iv) Presence of tail behind the anus stage.

Classification:
Chordata is divided into three subphyla:
(i) Urochordata
(ii) Cephalochordata
(iii) Vertebrata.

Essay Type Questions

Question 1.
Explain the classification of cryptogamae.
Answer:
Cryptogamae:
These are flowerless and seedless plants. They have hidden reproductive orgAnswer: They do not bear flowers and seeds externally.

They are divided into three divisions:

1. Thailophyta: They do not possess a stem, root or leaf and so called as thallus. Embryo formation after fertilization is absent. Their sex organs are single-celled. There is three clear group of plants in this division :
(A) Algae: Ulothrix, Cladophora, Ulva.
(B) Fungi: Aspergillus, Penicillium, Agaricus.
(C) Lichens: like Lichen perennail, Fruticose lichen.

2. Bryophyta:
The body of these plants are divided into structures like roots, stem or leaf. They grow on moist shady placed. Vascular tissue are absent in them. Their reproductive organs are multicellular. Embryo formation takes place after fertilisation.
Examples: Riccia, Funaria, Marchantia etc.

3. Pteridophyta:
The plant body is differentiated into root, stem and leaves. Vascular tissues are present in them. Their sex organs are multicellular. Embryo formation takes place after fertilization in them.
Examples: Fern (Pteris, selaginella).

Question 2.
Give the names of major phylurii with one or two features with examples.
Answer:
Major features with examples of the animal’s phylum are following:

Practical Work

Experiment 1.
To differentiate between monocots and dicots.

Procedure:
Take some seeds of wheat, gram, pea, maize, rice, tamarind and put into water. When they swollen completely, then classified and note in table. Those have one cotyledon (wheat, maize, rice) are monocots and those have two cotyledons (gram, pea, tamarind) are dicots. Make table to see other difference in them.

Quick Review of the Chapter

1. Father of Taxonomy is:
(A) Aristotle
(B) Robert Hook
(C) De-Candoli
(D) Carolus Linnaeus
Answer:
(D) Carolus Linnaeus

2. Which is not the base for the classification of organisms like Monera?
(A) cell structure
(B) nutrition
(C) body organization
(D) habitat
Answer:
(D) habitat

3. Which animal is not Monera?
(A) diatom
(B) bacteria
(C) microplasma
(D) blue-green algae
Answer:
(A) diatom

4. Respiration in reptiles takes place:
(A) by gills
(B) by skin
(C) by lungs
(D) by skin and slits
Answer:
(C) by lungs

5. Mammalia animal is:
(A) seahorse
(B) chameleon
(C) ostrich
(D) whale
Answer:
(D) whale

6. Skeleton is hollow in:
(A) pisces
(B) amphibians
(C) reptiles
(D) aves
Answer:
(D) aves

7. Who does not contribute in the classification of animals in a large kingdom ?
(A) Ernst Haeckel
(B) Robert Whittaker
(C) Carl Woese
(D) Darwin
Answer:
(D) Darwin

8. Which scientist divided the Monera Kingdom into Archaebacteria and Eubacteria?
(A) Eichler
(B) Carl Woese
(C) Haeckel
(D) Carolus
Answer:
(B) Car! Woese

9. Which of the following is a gymnosperm plant?
(A) mango
(B) pea
(C) cycas
(D) guava
Answer:
(C) cycas

10. Which of the follow ing has outer covering?
(A) unio
(B) pila
(C) chiton
(D) all of the above
Answer:
(D) all of the above

11. Which of the following group have mammary glands?
(A) aves
(B) mammals
(C) reptiles
(D) none of the above
Answer:
(B) mammals

Haryana State Board HBSE 9th Class Science Important Questions Chapter 6 Tissues Important Questions and Answers.

Haryana Board 9th Class Science Important Questions Chapter 6 Tissues

Very Short-Answer Type Questions

Question 1.
Are there same types of tissues in plants and animals?
Answer:
No, plants and animals have different types of tissues.

Question 2.
How are newly cells formed?
Answer:
Through cell division process.

Question 3.
What is called as unicellular organisms?
Answer:
All those organisms in which all the biological activities are fulfilled through single cell are called as unicellular organisms.

Question 4.
Which organisms undergo labour division?
Answer:
Multicellular organisms.

Question 5.
How many types of tissues are there in plants?
Answer:
Two types:
(i) Meristematic tissues
(ii) Permanent tissues.

Question 6.
Where are Meristematic cells found?
Answer:
Dividing cells (meristematic tissues) found at the tip of the shoot and at the tip of the root.

Question 7.
What is the function of meristematic tissue?
Answer:
Building up of new cells.

Question 8.
Do the permanent tissues have the ability of divide?
Answer:
No.

Question 9.
How many types of permanent plant tissues are there?
Answer:
Two types:
(i) Simple tissues
(ii) Complex tissues.

Question 10.
What are Parenchymatous tissues ?
Answer:
Parenchymatous tissues can be living and oval, rounded elongated or polygonal in shape. They have thin cell wall and the cells are isodiametric.

Question 11.
What are collenchymatous tissues ?
Answer:
Due to deposition of cellulose and Pectin at the angles of these tissues they get thinken in size. These tissues do not have intercellular spaces.

Question 12.
What are sclerenchymatous tissues ?
Answer:
These are dead cells. These cells do not have any intercellular space in them. They provide strength to the plant parts.

Question 13.
What are simple permanent tissues ?
Answer:
These tissues are formed of parenchymatous cells. Their origin, structural formation and function are same.

Question 14.
Which part of the plant consists of meristematic tissues ?
Answer:
Green part of the plant.

Question 15.
What are protective tissues made up of?
Answer:
By sclerenchymatous tissues.

Question 16.
Which parts of the plant consists of protective tissues.
Answer:
Leaves, flowers, stem and roots.

Question 17.
What is the other name of sclereids ?
Answer:
Brachysclereids or stone cells.

Question 18.
What is called as complex tissue ?
Answer:
Cells of different shape and size together form a group which works out a special function, is called as complex tissue.

Question 19.
How many types of complex tissues are there ?
Answer:
Two type:
(i) Phloem
(ii) Xylem.

Question 20.
Name the tissue that transports food in plants. [H.B.S.E. March, 2019]
Answer:
Sieve elements (phloem).

Question 21.
How many types of animal tissues are there ? Write their names.
Answer:
Four types:
(i) Epithelial tissues
(ii) Connective tissues
(iii) Muscular tissues
(iv) Nervous tissues.

Question 22.
Where are epithelial tissues found ?
Answer:
In the external and internal layers of animals.

Question 23.
Which tissue is called a protective covering in animals ?
Answer:
Epithelial tissue.

Question 24.
Which tissue is responsible for producing sperm and egg in animals ?
Answer:
Epithelial tissue.

Question 25.
What are the types of muscular tissues ?
Answer:
Three types:
(i) striated
(ii) unstriated
(iii) cardiac muscles.

Question 26.
Which muscles function according to owr will ?
Answer:
Voluntary muscles (Striated muscles).

Question 27.
Which type of muscles present in heart ?
Answer:
Cardiac muscles.

Question 28.
How many types of connective tissues are there ?
Answer:
Three.

Question 29.
Write two main functions of connective tissues ?
Answer:
Joining different organs and provide protection.

Question 30.
What are the types of skeletal connective tissues ?
Answer:
Two types:
(i) Bone
(ii) Cartilage.

Question 31.
Which tissue functions to connect bone to another bone?
Answer:
Ligaments.

Question 32.
What do tendons interconnect with?
Answer:
Muscle with bone.

Question 33.
Write down the name of the fluid tissue found in the body.
Answer:
Blood.

Question 34.
How many types of blood cells or corpuscles are found in blood?
Answer:
Three types of blood cells or corpuscles.
They are:
(i) Erythrocytes-Red Blood Cells (RBC)
(ii) Leucocytes: White Blood Cells (WBC) and
(iii) Blood Platelets.

Question 35.
What is the fluid part in blood called as ?
Answer:
Plasma.

Question 36.
What percentage of water is there in blood ?
Answer:
90%

Question 37.
Which tissues are brain, spinal cord and nerves formed of ?
Answer:
Nervous tissues.

Question 38.
What is nervous tissue called as ?
Answer:
Neuron.

Question 39.
What is the main function of neuron ?
Answer:
Sending impulses of messages.

Short-Answer Type Questions

Question 1.
Multicellular organisms are more superior in comparison of unicellular organisms. Why ?
Answer:
The unicellular organism can accomplish but a few functions and in doing that they are comparatively less expert to that of multicellular organisms. Among multicellular organisms by forming groups of lacs of cells not only those functions, rather they can perform more functions with complete skill, since they have the quality of labour-division in them.

Question 2.
Is there some difference between plants and animals tissues ?
Answer:
The plant tissues perform the function of supporting. Most of the tissues of plants are dead. The dead tissues too provide mechanical strength like the living tissues. They need little care of maintenance, where as the animals roam about here and there in search of companion, food and shelter. They consume more energy than plants. They possess maximum number of living tissues. Growth in some parts of the plants remains constrained, whereas in animals the case is different.

Question 3.
What are the different types of tissues found in plants ?
Answer:
Two types of tissues are found in plants:
(1) Meristematic tissues
(2) Permanent tissues

Question 4.
Write down the features of meristematic tissues.
Answer:
The features of meristematic tissues are as follows :
(1) Meristematic cells have same structure and their cell wall is thin.
(2) The shape of the cells is round, oval or polygonal.
(3) They are compactly arranged with each other and they don’t have any intercellular space in them.
(4) These cells have dense or sufficient cytoplasm (cell liquid) and a big nucleus.
(5) They have comparatively few vacuoles or no vacuole.

Question 5.
Where are meristematic tissues found in plants ?
Answer:
Meristematic tissues are found in the growing up parts of the plants only; Like-apical meristem and cambium (the region that increases thickness)

Question 6.
Write down the characteristics of permanent tissues.
Answer:
The characteristics of permanent tissues are as follows:
(1) Permanent tissues are formed of meristematic tissues.
(2) Their cells have no ability of division.
(3) They have a definite shapes.
(4) Their wall can be dead, thin or thick.
(5) They have enlarged cells and vacuolic cytoplasm.

Question 7.
Differentiate between meristematic tissue and permanent tissue.
Answer:
The difference between meristematic tissue and permanent tissue is as follows:
Meristematic Tissue:
1. They do not have intercellular space.
2. They have the ability of divide.
3. The are responsible for growth.
4. They are thin-walled and isodiametric.
5. They have an enlarged nucleus.

Permanent Tissue:
1. It can be or cannot be there in them.
2. They lack the ability of division.
3. They are no responsible for growth.
4. They are thin or thick-walled but not isodiametric.
5. They have small nucleus.

Question 8.
What are permanent tissues?
Answer:
Permanent tissues:
Permanent tissues are formed of meristematic tissues. Their tissues have no ability of division. Their size and volume is definite.

Permanent tissues are of two types:
(1) Simple tissues
(2) Complex or compound tissues.

Question 9.
Differentiate between parenchyma and collenchyma tissues.
Answer:
Following are the differences between parenchyma and collenchyma:
Parenchyma Tissue:
1. They are found in roots, stem and leaves.
2. Their walls are not thick.
3. They are formed of round and fine walled cells.
4. Their wall is made up of pectin and cellulose.
5. They helps in storing food and provide mechanical support.
6. They have intercellular space in them.

Collenchyma Tissue:
1. They are found in the middle vein of the stem and leaves.
2. Their walls are thick.
3. They have thick and elongated wall.
4. Their cell wall possesses collens of pectin.
5. They just provide mechanical support.
6. It is absent in them.

Question 10.
Enunciate different types of simple permanent tissues and write down the function of each. Answer: Simple permanent tissues are of three types :
(a) Parenchyma
(b) Collenchyma
(c) Sclerenchyma

(a) Functions of Parenchyma:
(i) Storing of food and assimilation.
(ii) To provide mechanical strength to the parts of plant.
(iii) Storing of resin, tanin, gum particles, and resin of morganie waste material.
(iv) Due to presence of chloroplast or chlorenchyma, they prepare food themselves.

(b) Functions of Collenchyma:
(i) They provide flexibility and strength to the plants.
(ii) Due to presence of chloroplast or chlorenchyma, they prepare glucose and starch.

(c) Functions of Sclerenchyma:
(i) They provide more strength to cartex and hard seeds.
(ii) They get transformed into protective tissues and protect the interior parts.

Question 11.
Differentiate among parenchyma, collenchyma and sclerenehyma.
Answer:
Parenchyma:
1. Their cell wall is constructed ot pectin and cellulose.
2. These are living cells.
3. Their function is food-storage and providing support.
4. They are found in root, stem and leaves.
5. They are formed of rounded thin walled cells.

Collenchyma :
1. Their cell wall is also formed of pectin and cellulose.
2. They too have living cells.
3. Their function is to provide mechanical support.
4. They are found in the middle vein of leaf and stem.
5. They are formed of multiarmed cells.

Sclerenchyma:
1. Their cell wall is formed of lignin.
2. Their cells are dead.
3. Their function is only to provide support
4. They are found in the stem and pulp of the fruits.
5. They are formed of thick-walled cells.

Question 12.
Describe Sclerenchvmatous tissue.
Answer:
Sclerenchyma:
These ceils are elongated in size and thin but are equipped with lignin. These are dead cells and are attached together. These cells are pointed at both ends. There is a clear mid lamella between adjacent cells. Cells consist of skewed regions that are called as pit canals. The cells provide strength to the parts of the plant.

Question 13.
Name different components found in Xylem (xylem tissues) components.
Answer:
The four components found in Xylem (xylem tissues) are as follows:
(1) Tracheids,
(2) Vessels,
(3) Xylem or wood Parenchyma
(4) Wood or Xylem fibers.

Question 14.
Give the importance of phloem in plants.
Answer:
Importance of Phloem: It is planted conductive tissue. It transports the starch (food) prepared by leaves to different parts of the plant.

Question 15.
Write functions of the Xylem (xylem tissues).
Answer:
Functions of Xylem:
It is too plant conductive tissue. It’s function is to transport the absorbed water and dissolved mineral salts by the roots to the leaves of the
plants and the apex. It also provide mechanical power to the plant.

Question 16.
Write short note on protective tissue.
Answer:
Protective Tissue:
Sclerenchyma found in the outermost parts of plants gets transformed into protective tissues. These tissues remain in the external layer of leaves, stems and roots. These tissues protect the interior tissues of plants. These tissues are covered with cutin. The cells of cork are dead. Cork is a lighter and protective tissue, it is more compressible and does not catch fire quickly.

Question 17.
What is stomata? Write its functions.
Answer:
Stomata:
They are found in the epidermal cells of the lower surface of leaves of plants which are called as stomatal pore. Stomata get protected by two guard cells.

Functions:
(1) Stomata are the nostrils of plants.
(2) Stomata plays a vital role in the exchange of gases and through them water loss takes place in plants.

Question 18.
Write names of different tissues found in animals.
Answer:
Animal tissues:
There are four types of tissues found in animals.
(1) Epithelial tissue
(2) Connective tissue
(3) Muscular tissue
(4) Nervous tissue.

Question 19.
Give the names and important functions of animal tissues.
Answer:
Animal tissue:
(a) Epithelial tissues:
Functions: They participate in absorption, secretion, protection, excretion, etc.

(b) Connective tissue:
Functions: This tissue participates in interlink the various parts of the body, provide support, turgidity, storage, protection and transportation.

(c) Muscular tissue :
Functions: Muscular tissue participates in motion, conduction, contraction, etc.

(d) Nervous tissue:
Functions: These do the main work of controlling and management.

Question 20.
Write a typical note on epithelial tissue.
Answer:
This is a covering or outer protective tissue that cover the body of an animal. Also, it protects a number of organs and cavities inside the body. Skin, alimentary can be capillary tube’s coat, food pipe, hollow organs of lungs all are formed of epithelial tissues. There is very’ narrow space. In these tissues, the cells are compactly arranged.

Question 21.
Classify Epithelial tissues.
Answer:
On the basis of shape and functions of the cells, epithelial tissues are classified into following types:
1. Squamous epithelium: These flat and disc like cells help in covering the organs of the body providing protection to them.
2. Cubical epithelium: These cubical or isodiametric cells are found in ducts of salivary glands and kidney tubules.
3. Columnar epithelium: The pillar or column like wide cells found in the layer of stomach and intestine.
4. Ciliated epithelium: Columnar and cubical shaped ceils germinate hair like structures at their ends that are called as cilia.
5. Glandular epithelium: These cells are found in secretory glands.

Question 22.
Write down the functions of Epithelial tissue.
Answer:
The functions of Epithelial tissue are the following :
(1) It performs the function to protect and cover the body organs
(2) It performs the functions of secretion, (in the Stomach and salivary glands)
(3) It produces sensitivity. (Eye and retinal cells)
(4) It produces sperm and egg.
(5) These absorb water and other salts.
(6) They also play role in excretion.

Question 23.
Write down the functions of connective tissue.
Answer:
The functions of connective tissues are as follows :
(1) These tissues join different organs of body with one another.
(2) They perform the function to tieup up organs of the body.
(3) These tissues give support to the organs of the body.
(4) Bone and cartilage build up the skeleton of the body.
(5) Adipose tissues store fat.
(6) These tissue perform the function of blood circulation.
(7) White blood corpuscles (WBC) fight against harmful bacteria.

Question 24.
What is Blood?
Answer:
Blood:
Blood is a liquid connective tissue. It tissue drift in liquid plasma (matrix). Blood cells are callei
(i) Red blood corpuscles (RBC)-Erythrocytes
(ii) White blood corpuscles (WBC)-Leucocytes
(iii) Blood platelets
Blood runs in each part of the body and thus, it connects all the parts of the body.

Question 25.
What are the functions of blood ? Explain.
Answer:
Functions of Blood:
(1) Red blood corpuscles receive oxygen from lungs and send it to different parts of the body.
(2) Blood collects hormones from the hormone glands and sends it to different parts.
(3) It helps in excreting excretory products from the body.
(4) White blood corpuscles or leucocytes protects from harmful bacteria.
(5) Blood checks the body temperature.
(6) Blood platelets clots the blood and avoid the more discharge of blood out of the body.

Question 26.
What is Bone? What are its types ?
Answer:
Bone: Skeletal tissue is connective tissue. In this tissue, ’/3 part organic and 2/3 part inorganic material is found. Its matrix consists of a peculiar type of protein ‘ossein’ which is in the form of collagen fibres. Bone possesses matrix osteoblasts, cytus, fibers and matrix have calcium phosphate, calcium carbonate and calcium fluoride. It give strength to the bone.

Question 27.
What is compact bone ?
Answer:
Compact bone:
This bone used to be strong and hard. Inside the matrix of bone, calcium salts provide hardness to the bone. Compact bone is formed of round and irregular dense layers of bones. Compact bone is found in the long shaft of bones like-femur. It involves Haversian canals.

Question 28.
Write down two differences each between bone and cartilage.
Answer:
Following are the differences between bone and cartilage :
Bone Cartilage:
1. It’s matrix is hard and flexible.
2. It’s matrix is formed of condin.
3. It is covered with pericondrium.
4. Haversian system is absent in it.

bone:
1. It’s matrix is too rigid and strong.
2. It’s matrix is formed of ossein.
3. It is covered with peraosteium.
4. Haversian system is present in it.

Question 29.
Write down the difference between tendon and ligament. Answer: Following are the difference between tendon and ligament:
Tendon:
1. It is flexible and moulding.
2. It connects muscle with bone.
3. It is made up of yellow fibre.

Ligament:
1. it is inflexible and hard.
2. It connects bone with another bone.
3. It is made up of white fibred connective tissues.

Question 30.
Write down the functions of bone, cartilage tendon and ligament.
Answer:
(i) Bone : It constructs the structure of body and protects the soft orgAnswer:
(ii) Cartilage: It constructs the skeletons of cartilaginous fishes. In our body the tip of nose and external ear (pinna), is formed of it.
(iii) Tendon : It connects muscle with bone.
(iv) Ligament: It joins bone with another bone.

Question 31.
Write down the functions of skeletal tissue.
Answer:
Skeletal tissue: Skeletal tissue is rigid, there is sufficient quantity of calcium salts in bone-matrix. Following are the significant functions of skeletal tissue:
(1) Skeletal tissue enshapes the body.
(2) Skeletal tissue protect the sensitive organs of the body.
(3) Skeletal tissue helps in joining muscles together.
(4) This tissue provides movement and locomotion to the body.
(5) In the middle of the bones erythrocytes (RBC) are produced.
(6) It provides surface for attachment of muscles (tendons and ligaments).

Question 32.
What is areolar tissue?
Answer:
Areolar tissue:
This tissue is found below the skin, between the muscles, blood vessels and around the nervous tissue. These cells possess jelly types transparent and sticky matrix. This is connective tissue. It interlinks body cavity and other parts of the body.

Question 33.
What is muscular tissue ? What are its types ?
Answer:
Muscular tissue:
The cells of these tissues are elongated, spindle shaped and unbranched. Cardiac muscles are branched. Muscular tissues are found in different sizes. Muscular tissues provide locomotion and movement to different parts of body.

Muscular tissues are of three types :
(a) Striated muscles. (Skeletal or voluntary muscles)
(b) Unstriated muscles. (Smooth muscles or involuntary muscles)
(c) Cardiac muscles.

Question 34.
Make difference between striated muscles arid cardiac muscies.
Answer:
The differences between striated muscies and cardiac muscles are as follows:
Striated muscle:
1. These muscles work accordingly to our will i.e., they are voluntary muscles.
2. These muscles are jointed with bones.
3. They are unbranched.
4. They have a number of nuclei.
5. They have light or dark bands on them.

Cardiac muscle:
1. These muscles are involuntary, they do not work accordingly to our command.
2. These muscles are found in the heart.
3. They are branched.
4. They have one or two nuclei.
5. They have transverse indistinct light bands which show faint cross striations.

Question 35.
Describe the structure of skeletal and cardiac muscles.
Answer:
Skeletal Muscles:
We can move some muscles by the conscious will. Muscles present in our limbs move when we want them to, and stop when we so decide. Such muscles are called voluntary muscles. These muscles are also called skeletal muscles as they are mostly attached to bones and help in body movement. Under the microscope, these muscles show alternative light and dark bands or striations when stained appropriately. As a result, they are also called striated muscles. The cells of this tissue are long, cylindrical, unbranched and multinucleate (having many nuclei).

Cardiac Muscles: The muscles of the heart show rhythmic contraction and relaxation throughout life. These involuntary muscles are called cardiac muscles. Heart muscle cells are cylindrical, branched and uninucleate.

Essay Type Questions

Question 1.
What is called a tissue ? How many types of plant cells are there ? Describe meristematic tissues.
Answer:
Tissue:
A group of several cells that have common origin, structure and function is called a tissue. In plants there are two types of tissues.
(i) Meristematic tissues
(ii) Permanent tissues.

Meristematic Tissue:
In these tissues, division of cells takes places continuously and these cells that have the ability to divide, they keep on reproducing newly cells. Meristematic tissues are found only in those parts that participate in the growth process like tip of the shoot-root, and cambium. Due to these tissues, the length and thickness of the plants get increased.

On the basis of origination, meristematic tissues are of two types:
(i) Primary meristematic tissues.
(ii) Secondary meristematic tissues.

On the basis of position meristematic tissues are of three types:
(a) Apical meristem: They are found at the tip of the root, stem and branches; They are also of three types:
(1) Epidermis: These tissues buiid up the outer skin of the plant.
(2) Cortex: These tissues buiid up the filling up system.
(3) Hypodermis: These tissues make transport tissues, phioem and xylem,
(b) Intercalary meristem: This tissue is found in the stem of monocotyledones. Due to activity of this tissue plant grow up in height.
(c) Lateral meristem: This tissue is found in the stems and root of dicotyledones.

Question 2.
How many types of simple tissue of plant are there ? Explain them.
Answer:
Simple tissue When the meristematic tissues totally lose the ability of division, then they transform into permanent tissues. Permanent tissues are of two types: Simple tissues and complex tissues. Simple tissues are formed of only one type of same structural cells. Their function is also same. On the basis of structure these tissues are of three types:

(i) Parenchyma:
These tissues are found in the shoot system (stem, leaves and flower) and root in plants. In the green part of the plant their number used to be more. These cells can be round, elongated or polygonal shape. These are living cells. Their cell wall is thin and is made up of cellulose. These cells contain dense protoplasm. The main functions of these tissues are storage of food, assimilation, provide strength, storing of resin tanin and gum and many times preparing food too.

(ii) Collenchyma:
These cells too are living. These are multiarmed, oval and rounded shaped. Their cell wall is thin, but at the corners of the cell due to deposition of cellulose and pectin they get hard or stout. In these cells generally there are some chloroplasts. This tissue brings flexibility and strength in plants and prepare glucose and starch due to presence of chloroplast in it.

(iii) Sclerenchyma:
These cells are elongated in size and thin but are equipped with lignin. These are dead cells and are attached together. These cells are pointed at both ends. There is a clear mid lamella between adjacent ceils. Cells consist of askewed regions that are called as pit canals. The cells provide strength to the parts of plant.

Question 3.
What is called as complex tissues ? What are their types in plants ? Explain each of them.
Answer:
Complex Tissue:
Complex tissue is a group of more than one type of cells which perform a special function. Complex tissue is of two types :
(1) Xylem: Xylem is a transport tissue. It transports water and dissolved mineral salts from root to the shoot-system. All the cells of this tissue are dead, thick walled and lignified. This tissue is formed of with the combination of four cells.
(i) Trachieds
(ii) vessels
(iii) xylem or wood-parenchyma
(iv) xylem fibres.

(2) Phloem:
It is a living transport tissue. Starch prepared due to photosynthesis process is transported to different parts of the plant by it. This tissue is also formed of with the combination of four components :
(i) Sieve tubes
(ii) companion cells
(iii) phloem parenchyma
(iv) phloem fibres.
Out of these sieve tubes are significant. These sieve tubes consist of porous wall that send food from the leaves to different parts of the plant.

Question 4.
What is called as nervous tissue ? How many types does it have ?
Or
Define the neuron with diagram.
Answer:
Nerve cells (neurons): It is a specialised elongated cell which is the basic unit of conduction of impulses Tn this cell there a nucleus surrounded with cytoplasm. Many small branches project out of cytoplasm, which are called as dendrites. One of these branches is the longest one which is called as Axon. Axon carries the impulses away from cells. One nerve cell does not directly join with the another neuron. They have some empty space between them in which there is a very closed transportation. It is called as synapses.

If we have pain in our hand, this information gets collected by the dentrites of the sensory neuron located in the hand. The sensory neuron converts it into electric signal. This signal is transmitted by the motor neurons and passing through synapse reaches the brain. The brain on receiving the impulse reacts to that. The motor nerve carries this reaction to the muscles of the hand and thus, the muscles of the hand make suitable reaction.

Thus, nerve cells (neurons) are of three types:
1. Sensory nerve cells (neurons): They carry sensations in different parts of the body towards brain.
2. Motor neurons: These receive message from the brain and further send it to the muscles.
3. Multipolar neurons: They does both the functions they carry sensations towards brain and further carry the commands of brain towards the muscles.

Question 5.
What is blood (human blood) ? Explain its constituents.
Answer:
Blood: Blood is liquid connective tissue which is red in colour. Blood circulates in the organs of body, thus it can be said that it connects the entire parts of the body together.

Human blood has mainly two constituents:
(A) Plasma: This is a substance in the blood which is light yellow in colour. It contains 90% of water. The remaining salts, glucose, amino acid, protein, hormone, oxygen, carbon dioxide gas and certain digested undigested food materials are also found in it.

Function: It consists of fibrin named protein, that helps in coagulation or clotting of blood. It also consists anti bodies which destroy foreign bodies harmful bacteria etc.

(B) Blood corpuscles (Blood cells): There are three types of corpuscles found in blood which are described as ahead:

(a) Red Blood Corpuscles or Erythrocytes: These are round in shape. Each red corpuscle has the life time of nearly four months. They have a substance namely haemoglobin in them which provides red colour to blood. They are round in shape, flat and small in size. They have no nucleus in them. They have the largest number (50 lakh oer cubic milliletre).

Functions:
(i) Red blood corpuscles provide red colour to the blood.
(ii) Their haemoglobin distributes oxygen throughout the body. On receiving oxygen these corpuscles i become oxy-haemoglobin.

(b) White Blood corpuscles or Leucocytes : The number of white blood corpuscles is lesser than red blood corpuscles, but they are bigger in size than them. They are white in colour, since they have no haemoglobin in them. Therefore they do not have a definite shape. They also have nucleus. They are of five types.
Function: They kill the harmful bacteria in the body and gobble them up. Thus, they protect us from diseases.

(c) Thrombocytes or Platelets: They are thick in the centre and thin at the ends. They are very small. They also have nucleus.
Function: They help in coagulation of blood. When in case of injury, blood oozes out from the wound, these platelets gather around the injury and by a chemical action clot there, so that there might not be any more bleeding.

Practical Work

Experiment-1:
Observing the structure of stem by cutting it in a transverse section (T.S.).

Procedure:
(i) Peel off a thin slice or transverse section of a thin and soft stem of a plant, keep it into the safranine solution.
(ii) Take a slice of stem section and keep it on a glass slide carefully leave a drop of glycerine on it and cover it with a coverslip.
(iii) Observe the prepared slide under the compound microscope and draw a sketch diagram of the setting up of the cells that you observe.

Quick Review of the Chapter

1. Blood transports
(A) oxygen
(B) food
(C) harmones and waste substances
(D) all of the above
Answer:
(D) all of the above

2. Nearly all tissues of are dead.
(A) plants
(B) animals
(C) both (A) and (B)
(D) saprophytes
Answer:
(A) plants

3. New cells in plants are formed by tissues.
(A) parenchyma
(B) collenchyma
(C) meristematic
(D) sclerenchyma
Answer:
(C) meristematic

4. Which of the follow ing is not the characteristic of meristematic?
(A) highly active
(B) more cytoplasm
(C) vacuole present
(D) distinct nucleus
Answer:
(C) vacuole present

5 tissues are found in the growing up parts of root and stem.
(A) Parenchyma
(B) Meristematic
(C) Sclerenchyma
(D) Collenchyma
Answer:
(B) Meristematic

6. The helpful tissue in photosynthesis is :
(A) parenchyma
(B)
(C) sclerenchyma
(D)
Answer:
(A) parenchyma

7 tissues carries the function of storage.
(A) collenchyma
(B)
(C) sclerenchyma
(D)
Answer:
(B) parenchyma

8. The tissues which makes a plant hard and strong is :
(A) collenchyma
(C) parenchyma
Answer:
(B) sclerenchyma

9. Which tissues make up the husk of coconut ?
(A) sclerenchyma
(C) parenchyma
Answer:
(A) sclerenchyma

10. Sclerenchyma is found in the of a plant.
(A) stem
(B) near vascular bundle
(C) buds of leaves and seeds
(D) all of the above
Answer:
(D) all of the above

11. Holes/pores are found :
(A) on the surface of leaf
(B) in vessels
(C) in xylem
(D) in phloem
Answer:
(A) on the surface of leaf

12. Which of the following is not a function of epidermis ?
(A) reduces the loss of water
(B) protects from mechanical shocks against water cell
(C) helpful in entry of parasite fungi
(D) all of the above
Answer:
(C) helpful in entry of parasite fungi

13. The shape of protective cells/tissues in stomata is
(A) like liver
(B) like kidney
(C) like the seed of bean
(D) like the seed of gram
Answer:
(B) like kidney

14. The function of stomata is:
(A) evaporation
(B) intake and release of oxygen
(C) intake and release of carbon dioxide
(D) all of the above
Answer:
(D) all of the above

15. The capacity of water absorption in roots increases by:
(A) increase in the size of root
(B) increase in the length of root
(C) due to hair roots present on roots
(D) all of the above
Answer:
(C) due to hair roots present on roots

16. What makes bark impermeable for air and water ?
(A) waxy cover
(B) thick layer of bark
(C) chemical named subrin
(D) all of the above
Answer:
(C) chemical named subrin

17. The example of complex tissue is:
(A) xylem
(B) meristematic
(C) phloem
(D) both (A) and (C)
Answer:
(D) both (A) and (C)

18. ………….. is Conductive tissue.
(A) xylem
(B) phloem
(C) both (A) and (B)
(D) neither (A) nor (B)
Answer: (C) both (A) and (B)

19. The parts of xylem are:
(A) tracheids
(B) vessels
(C) xylem parenchyma and fibre
(D) all of the above
Answer:
(D) all of the above

20. The parts of phloem are:
(A) sieve tubes
(B) companion cells
(C) phloem parenchyma and fibres
(D) all of the above
Answer:
(D) all of the above

21. Minerals and water are transported by:
(A) phloem
(B) xylem
(C) sieve tube
(D) companion cells
Answer:
(B) xylem

22. Phloem conducts:
(A) synthesised food
(B) mineral salts
(C) water
(D) all of the above
Answer:
(A) synthesised food

23. Which tissue is not a simple tissue?
(A) sclerenchyma
(B) phloem
(C) parenchyma
(D) collenchyma
Answer:
(B) phloem

24. Which tissue is not an animal tissue?
(A) epithelial
(B) epidermal
(C) connective
(D) muscular
Answer:
(B) epidermal

25. Which tissue carries the function of covering the body and making covers for different organs inside the body?
(A) epithelium
(B) connective
(C) nervous
(D) muscular
Answer:
(A) epithelium

26. Which one is not a type of epithelium tissues?
(A) squamous
(B) cubical
(C) rounded
(D) columnar and ciliated
Answer:
(C) rounded

27. Which tissue forms the difference of alimentary canal and mouth?
(A) glandular
(B) squamous
(C) columnar
(D) cubical
Answer:
(B) squamous

28. What kind of tissue is blood?
(A) epithelium
(B) connective
(C) muscular
(D) nervous
Answer:
(B) connective

29. Which blood cells carries the function of intake of oxygen?
(A) RBC
(B) WBC
(C) platelets
(D) all of the above
Answer:
(A) RBC

30. Bone is an example of what type of tissue?
(A) epithelium
(B) connective
(C) muscular
(D) nervous
Answer:
(B) connective

31. The tissue which provides motion to body is:
(A) epithelium
(B) connective
(C) muscular
(D) all of the above
Answer:
(C) muscular

32. The feature of voluntary muscle is:
(A) long in size
(B) cylindrical
(C) unstriated
(D) all of the above
Answer:
(D) all of the above

33. Involuntary muscles are not found in:
(A) bones
(B) eyelids
(C) urinal
(D) trachea of lungs
Answer:
(A) bones

34. Which cell can be longest?
(A) epithelium
(B) nervous
(C) connective
(D) muscular
Answer:
(B) nervous

35. Which tissue rs found in heart?
(A) muscular
(B) nervous
(C) epithelium
(D) connective
Answer:
(A) muscular

Haryana State Board HBSE 9th Class Science Important Questions Chapter 5 The Fundamental Unit of Life Important Questions and Answers.

Haryana Board 9th Class Science Important Questions Chapter 5 The Fundamental Unit of Life

Very Short-Answer Type Questions

Question 1.
Who discovered the first cell and when?
Answer:
A scientist named Robert Hooke discovered the cell in 1665.

Question 2.
What was discovered by Leeuwenhoek?
Answer:
Leeuwenhoek discovered bacteria cells in 1674 with the help of a microscope.

Question 3.
Which scientist gave the name protoplasm to the living material inside the cell?
Answer:
J.E. Purkinje in 1939.

Question 4.
Which scientists proposed cell theory?
Answer:
M.Schleiden (1838) and T. Schwann (1839).

Question 5.
What is a cell ?
Answer:
The cell is the structural and functional unit of living organisms.

Question 6.
Which scientist expanded cell theory?
Answer:
Virchow (1855).

Question 7.
When was the electron microscope discovered?
Answer:
In 1940.

Question 8.
What is a unicellular organism?
Answer:
When a single cell of the organism performs all the life functions, it is called a unicellular organism.

Question 9.
What is a multicellular organism?
Answer:
When more than one cell group together to form an organism, it is called a multicellular organism.

Question 10.
Give some examples of unicellular organisms.
Answer:
Amoeba, Euglena, Entamoeba, Paramoecium.

Question 11.
Name one multicellular organism.
Answer:
Man.

Question 12.
Name the longest cell.
Answer:
Nerve cell.

Question 13.
Name the smallest cell.
Answer:
Mycoplasma galisepticum.

Question 14.
Which is the largest cell?
Answer:
Ostrich egg.

Question 15.
Name the smallest cell found in the human body.
Answer:
Lymphocyte.

Question 16.
Name the largest plant cell.
Answer:
Acetabularia.

Question 17.
Which cell organelle is responsible for protein synthesis?
Answer:
Ribosome.

Question 18.
In which organism is a division of labour found?
Answer:
In multicellular organisms.

Question 19.
What are cell organelles?
Answer:
In every cell, some specific components perform specific functions. They are called as cell organelles.

Question 20.
Cell organelles group together to form which unit?
Answer:
Cell.

Question 21.
Name the main functional zones oLa cell.
Answer:
The plasma membrane, nucleus cytoplasm.

Question 22.
Name one special feature of plasma membrane.
Answer:
Selective permeability.

Question 23.
What is osmosis?
Answer:
The movement of water or some other liquid substance from a region of high concentration to a region of low concentration through a semi-permeable membrane is called osmosis.

Question 24.
Give one example of osmosis.
Answer:
Absorption of water by plant roots.

Question 25.
Why does kishmish (dried raisin) get swollen in kheer?
Answer:
As the protoplasm of the kishmish is more concentrated than the kheer, internal osmosis takes place due to which it gets swollen.

Question 26.
What is diffusion?
Answer:
The movement of a substance from a region of high concentration to a medium of low concentration is called diffusion.

Question 27.
What happens when a cell is kept in a hypertonic solution?
Answer:
The cell will lose water by osmosis.

Question 28.
What is the membrane called which allows only specific substances to pass through it?
Answer:
Semi-permeable membrane.

Question 29.
What is plant cell wall made of?
Answer:
Cellulose.

Question 30.
Which cell organelle controls the activities of the cell?
Answer:
Nucleus.

Question 31.
Write the full form of RNA.
Answer:
Ribonucleic acid.

Question 32.
Write the full form of DNA.
Answer:
Deoxyribonucleic acid.

Question 33.
What is a gene?
Answer:
The functional unit of a chromosome is called a gene.

Question 34.
Which is the carrier of hereditary characters ?
Answer:
Chromosome.

Question 35.
How many chromosomes are found in man ?
Answer:
23 pairs or 46 chromosomes.

Question 36.
Name two cell organelles.
Answer:
Mitochondria, Golgi apparatus.

Question 37.
Which cell organelle is knows as suicide bag?
Answer:
Lysosome.

Question 38.
Name one secretive organelle of cell.
Answer:
Golgi apparatus.

Question 39.
Name the powerhouse of cell.
Answer:
Mitochondria.

Question 40.
What is ATP?
Answer:
ATP is the energy of the cell.

Question 41.
Name an organelle which is found only in plant tissue.
Answer:
Plastids.

Question 42.
Name the organelle which is helpful in cell division.
Answer:
Centrosome.

Question 43.
What are prokaryotic cells ?
Answer:
The cells which are small, have no cell organelle and have only one chromosome, are called prokaryotic cells.

Question 44.
What are eukaryotic cells ?
Answer:
Cells which are large in size, have cell organelle and more than one chromosome are called eukaryotic cells.

Question 45.
What is the green colour of plants due to ?
Answer:
Due to green pigment.

Question 46.
Name a prokaryotic cell.
Answer:
Bacteria.

Question 47.
Name a eukaryotic cell.
Answer:
Animal or plant cell.

Question 48.
What is cytoplasm ?
Answer:
The substance enclosed by the plasma membrane is called cytoplasm.

Question 49.
What is protoplasm ?
Answer:
Cytoplasm and nucleus together constitute protoplasm.

Question 50.
How many types of endoplasmic reticulum are there ?
Answer:
Two types:
(i) Rough Endoplasmic Reticulum (RER),
(ii) Smooth Endoplasmic Reticulum (SER).

Question 51.
What is the main function of SER ?
Answer:
To Synthesis lipid molecules.

Question 52.
What does ER denote ?
Answer:
Endoplasmic Reticulum.

Question 53.
Which organelle detoxifies toxic substances and drugs in the liver cells ?
Answer:
SER.

Question 54.
Name coloured plastids.
Answer:
Chromoplast.

Question 55.
Name a white and colourless plastid.
Answer:
Leucoplast.

Question 56.
Which plastid contains chlorophyll ?
Answer:
Chloroplast.

Question 57.
Are the vacuoles present in plants smaller or larger (in size)?
Answer:
Larger.

Short-Answer Type Questions

Question 1.
What is a cell ?
Answer:
Just as a house is made up of small bricks, living organisms are formed of small units called cells. Cell is the structural and functional unit of each living organism cell has its own organisation.

Question 2.
Write a note on the size of the cell.
Answer:
The size of the cell is so small that it is difficult to see it. It can be seen under a microscope, but to see and measure its structural organisation, a special unit called micron (p) on a micrometre is used. A micron is the l/000th part of a millimetre. Generally cells are around 30 microns in size. The smallest cell is mycoplasmas galisepticum and the largest cell is the egg of ostrich which is 170 x 135 mm in size. The size of pleuropneumonia is 0.1 pm. The size of the cell depends on the function it performs.

Question 3.
What is cell theory (principal) ?
Answer:
Cell is the basic unit of life. This is the cell theory. According to this theory, all living organisms are made up of cells. Cell is the functional and structural unit of life. Cell is a body containing protoplasm. Cell theory was proposed by M. Schleiden (1838) and T. Schwann (1839) after studying plant and animal cells. Afterwards, in 1855, Virchow expanded the cell theory by saying, ‘The new cells are formed from division of pre-existing cell.’ This is the cell theory.

Question 4.
What are unicellular and multicellular organisms ?
Answer:
1. Unicellular organisms:
The organisms which are formed of single cell are called unicellular organisms; e.g. amoeba, fungi, chlamydomonas, paramoecium, euglena etc.

2. Multicellular organisms:
The organisms which are formed of many cells grouped together are called multicellular organisms; e.g. hydra, whale, sponge, ferm, man, tagetus, fish, etc.

Question 5.
Draw a labelled diagram of the cells of onion peel as seen under a microscope.
Answer:
Cells of onion peel:

Question 6.
Draw a labelled diagram of various cells found in human body.
Answer:
Different cells of human body

Question 7.
What are the major differences between the cells of unicellular and multicellular organisms ?
Answer:
The main differences between the cells of unicellular and multicellular organisms are :
(1) The cell of a unicellular organism is generally circular or oval, while the cells of multicellular organisms are cylindrical.

(2) As a unicellular organism is made up of a single cell, all the life activities are performed by this single cell. On the other hand in multicellular organisms, all cells perform certain specific functions.

(3) As all the life activities are performed by a single cell in unicellular organisms, these activities are not performed efficiently. But division of labour is found in the cells multicellular organisms. Different cells perform specific functions, which they do efficiently.

(4) Amoeba, Paramoecium, etc. are unicellular organisms while dog, frog, man, etc. are multicellular organisms.

Question 8.
What are the advantages of multicellularity ?
Answer:
Multicellularity has a lot of advantages. Because of multicellularity, division of labour is found in higher animals. Because of difference in the types of cells, various cells perform specific functions in these organisms. All the cells co ordinate with each other. Thus, all the activities relating to growth and development depend upon the co ordination between all the cells.

Question 9.
What are the differences between plasma membrane and cell wall ? Give their functions also.
Answer:
Differentiate between Plasma Membrane and cell wall are as follows :
Plasma Membrane:
1. It is living.
2. It is formed of proteins, and lipid peptides.
3. It is smooth and flexible.
4. It is semi-permeable.

Cell Wall:
1. It is non-living.
2. It is formed of cellulose, lignin and pectin.
3. It is hard.
4. It is permeable.

Functions:
Plasma Membrane: Only molecules of definite size can pass through it. It is semi-permeable. It is a protective covering of the cell.

Cell Wall: It provides shape, size and protection to the cell.

Question 10.
What happens when we put an animal cell or a plant cell into a sugar solution ?
Answer:
The following can happen if we put a living cell in sugar solutions having different concentration:
(1) When put in a hypotonic solution, water will enter the cell by osmosis.
(2) When put in an isotonic solution,there will be no net movement of water through the cell membrane.
(3) When put in a hypertonic solution, the water will come out of the cell through osmosis.

Question 11.
How is diffusion important for a cell ?
Answer:
Diffusion plays an important role for the entry and exit of water and gases in and out of the cell. It helps the cell to get nutrition from the outside environment. The entry and exit of various molecules and in and out of the cell takes place by diffusion only.

Question 12.
What is cell wall ?
Answer:
Cell Wall: Cell wall is found only in plant cells. Some bacteria also possess cell wall. As the cell wall is made up of cellulose, it is permeable to water. Because of hardening of cellulose, it is non-living.

Question 13.
Write the advantages and disadvantages of cell wall.
Answer:

Advantages:
(1) It provides a definite shape to the cell.
(2) The cell remains structurally strong and protected.
(3) The plasma membrane remains protected.
(4) Because of its permeability, the cell wall maintains balance of different materials inside the cell.
(5) It prevents the cell from the attack of disease causing molecules.
(6) It provides a definite structure to the cell.

Disadvantages:
(1) The pace of cell division gets slowed down because of cell wall.
(2) It reduce the expanding power of cell.

Question 14.
Write a note on protoplasm shrinkage.
Answer:
If a plant cell is kept in a hypertonic solution, then exosmosis starts, i.e. water starts coming out of cytoplasm, due to which the cell wall loosens. If the hypertonic solution is highly concentrated, then the shrinkage of protoplasm continues. This process is called protoplasm shrinkage.

Question 15.
What are the main functional zones of a cell ?
Answer:
The main functional zones of a cell are plasma membrane, cysoplasm and nucleus which perform the following functions : ‘
1. Plasma membrane: It is the outer covering of every cell. It is made of lipids and proteins. It protects the cell and controls the movement of molecules inside and outside the cell.

2. Cytoplasm: Apart from the nucleus it constitutes the remaining part of the cell. It has various cell organelles like Golgibodies, mitochondria, endoplasmic, reticulum, ribosomes, lysosomes and cnloroplasts which perform various functions.

3. Nucleus: It is the main part of the cell, circular of oval-shaped. It controls all the activities of the cell. It contains nucleoplasm, nucleolus and chromosomes. Nucleus is covered by nuclear membrane.

Question 16.
Name the main cell organelles.
Answer:
The main cell organelles are:
(1) Endoplasmic Reticulum
(2) Ribosomes
(3) Lysosomes
(4) Mitochondria
(5) Nucleus
(6) Golgibodies
(7) Cilia and Plagella
(8) Vacuoles
(9) Plastids
(10) Centrosomes
(11) Perotisomes.

Question 17.
Write a note on nucleus.
Answer:
Nucleus is circular and the largest cell organelle found in the centre of cytoplasm. It controls and co ordinates all the activities of a cell. Nucleus is surrounded by nuclear membrane which is filled by nucleoplasm. Nucleolus and chromosomes are present in the nucleoplasm. There are some cells which possess many nuclei. These are called coenocytes.

Question 18.
Give four functions of nucleus.
Answer:
Functions of nucleus :
(1) It controls all the activities of the cell.
(2) It controls cell division.
(3) It takes part in reproduction.
(4) It maintains the functional ability of the cell.

Question 19.
Name both the nucleic acids present in the cell. What functions do they perform ?
Answer:
(1) DNA (Deoxyribose nucleic acid),
(2) RNA (Ribose nucleic acid).

(i) Functions of DNA: It contains genes. DNA stores the hereditary characters and passes these characters to the next generation. So, it is the hereditary material.
(ii) Functions of RNA: It synthesises proteins. In many types of viruses, RNA also acts as the hereditaiy material.

Question 20.
Write a note on Gene.
Answer:
Small granular structures present on the chromosomes are called genes. Genes are always found in pail’s on the chromosomes. One pair of genes controls one character. For example, our height is decided by a pair of two genes present in our body. Similarly, other characters/features of our body, like skin colour, colour of the eyes, etc. develop from a pair of genes each.

Question 21.
What are genes ? What is their function ?
Answer:
Gene:
Gene is a part of deoxyribonucleic acid (DNA). They are present on the chromosome, one above the other, in a specific order. Gene is the hereditary unit of life. In living organisms one character is controlled by one pair of genes. Genes hold the chloroplasts together.

Question 22.
Describe prokaryotic and eukaryotic cells.
Answer:
Prokaryotic and eukaryotic ceils are of following types:
1. Prokaryotic ceils: Pro means primitive (primary) and karyon means nucleus. These cells do not possess nuclear membrane. Only one chromosome is found in these ceils. The cell organelles are not enclosed by a membrane in these cells, like blue-green algae, bacterial cell.

2. Eukaryotic cells: Eu means continuous and karyon means nucleus. These cells have a well-defined nucleus which is enclosed by a nuclear membrane. More than one chromosomes are present in these cells, like plant and animal cells.

Question 23.
Define the following :
Protoplasm, cytoplasm, nucleoplasm.
Answer:
(i) Protoplasm : All the substances present inside the cell membrane constitute protoplasm. Protoplasm is the very basis of life. It performs all the activities of life.
It has two parts:
(a) Nucleus
(b) Cytoplasm.

(ii) Cytoplasm : Apart from the nucleus, the remaining part of the protoplasm is called cytoplasm. It contains living as well as non-living material. Many cell organelles are present in the cytoplasm i.e. Mitochondria, ribosomes, Golgibodies, lysosomes, vacuoler, endoplasmic reticulum etc.

(iii) Nucleoplasm : It is found inside the nucleus in which proteins, nucleolus, enzymes and chromosomes are present.

Question 24.
Write a note on Endoplasmic Reticulum (E.R.) Or White down the functions of Endoplasmic Reticulum (E.R.).
Answer:
Near the nucleus, a large network of membrane-bound tubes is found, which is called endoplasmic reticulum. These look like long tubules or round or oblong bags (vesicles). ER is of two types:
(i) Rough Endoplasmic Reticulum (RER),
(ii) Smooth Endoplasmic Reticulum (SER).
ER helps in intracellular transport of materials. It also acts as a cytoskeleton for some bio-chemical reactions. In the liver cells of vertebrates it plays a crucial role in detoxifying many poisons and drugs.

Question 25.
Differentiate RER and SER.
Answer:
Differences between RER and SER as below:
RER (Rough Endoplasmic Reticulum)
1. They are present on the surface of the ribosomes.
2. They, lie near the nucleus.
3. They help in photosynthesis.

SER (Smooth Endoplasmic Reticulum):
1. They don’t have any ribosomes.
2. They are present near the plasma membrane.
3. They help in lipid synthesis and in the formation of plasma membrane.

Question 26.
Write a note on Golgibodies.
Answer:
Golgibodies were first described by Camillo Golgi. The substance secreted by Golgibodies is accumulated in the vacuoles. Golgibodies form the cell wall. They are made up of vesicles, vacuoles and tubules. They are called golgi complex or golgi apparatus. It packages the materials produced by the ER and despatches it outside the cell.

Question 27.
Which cell organelle is called digestive bag and why ?
Answer:
Lysosome functions as a digestive bag in the cell.
Lysosomes occur in all the cells. These are spherical structures enclosed by a green coloured membrane. These contain many membrane bound small vesicles which are filled with catabolic substances lenzymes, also which are called as digestive bags which contain enzymes. These vesicles digest organic substances in the cell. These work as intercellular digestive system.

Lysosomes also function in digestion of food particles as well as worn-out cell organisms as a result of which old cells die. Therefore, they are also called ‘suicidal bags’ because during disturbances in cellular metabolism, when the cell gets damaged, lysosomes burst and the enzymes digest their own cell. RER make the digestive enzymes of the lysosomes.

Question 28.
Write a note on lysosomes.
Answer:
Lysosomes: Lysosomes are sac like structures which are also called as suicidal bags. They are found in all cells. In each cells, there are over one hundred lysosomes. They were discovered by D. Dueve, a scientist, in 1955. Their function is the elimination of some disturbances in the cell as well as destruction of foreign particles. Many digestive enzymes are found in them due to which they are also called digestive enzymes.

Question 29.
What is a centrosome ?
Answer:
Centrosome: Centrosome is a spherical structure found near the nucleus. It is found only in animal cells and is totally absent in plant cells. It contains one or two centrioles. In plant cells, polar caps are present instead of centrosomes. Centrosome play an important role in cell division.

Question 30.
Write a note on ribosomes.
Answer:
They are made up of RNA and proteins. These extremely small bodies are either scattered freely in the cytoplasm or are attached on the outer surface membrane of the rough endoplasmic reticulum. In the cell, ribosomes systhesise proteins with the help of amino acids.

Question 31.
Write a note on mitochondria.
Answer:
Mitochondria is a spherical or rod-shaped important organelle of the cell bounded by two membranes. The outer membrane is smooth but the inner layer contains folds. These folds are called cristae. In between the two membranes, a fluid called matrix is present. Mitochondria produces respiratory enzymes. It also oxidises food to produce energy, so it is also called as energy house or power house of the cell.

Question 32.
Differentiate the structural organisation of lysosomes and mitochondria.
Answer:
Differences between the structural organisation of lysosomes and mitochondria are as follows :
Lysosomes:
1. These are sac like structures
2. These are enclosed by a single membrane.
3. They do not bear any folds on the inner surface.
4. They contain digestive enzymes, which digest the food material.
5. They do not contain DNA.

Mitochondria:
1. These are spherical or rod-shaped organelles.
2. These are enclosed by a double membrane.
3. They bear folds on the inner surface, which are called cristae.
4. They contain some specific enzymes, which help in respiration.
5. They contain DNA.

Question 33.
Give differences between the functions of lysosomes and mitochondria.
Answer:
Differences between the functions of lysosomes and mitochondria as follows :
Lysosomes
1. They produce energy by digesting stored food in the times of emergency.
2. They do not contain ATP.
3. The destroy viruses and bacteria.
4. They function to destroy old and damaged cell organelles.
5. Through destructive process, they destroy the unwanted materials and are also called as suicidal bags.

Mitochondria
1. They produce energy through respiration.
2. They store energy in ATP and release it according to the requirement.
3. They do not do so.
4. They are not capable to perform such functions.
5. They do not perform any protective functions.

Question 34.
Write any five differences between ribosomes and centrosomes.
Answer:
Differences between ribosomes and centrosomes are as follows:
Ribosomes:
1. These are granular and spherical structure.
2. These are found both in plant and animal cells.
3. They synthesise proteins from the amino acids.
4. They do not take part in cell division.
5. They are found either scattered freely in the cytoplasm or attached to the Rough Endoplasmic Reticulum.

Centrosomes:
1. These are small star-like structure present outside the nuclear Wall.
2. These are found only in the animal cells.
3. They do not take part in protein synthesise.
4. They form Aster Rays at the time of cell division.
5. They occur in pairs near the nucleus.

Question 35.
Write a brief note on chloroplasts.
Answer:
Chloroplast is found in all green-coloured plants. It a double membrane cell organelle on the inner membrane of which are found flat structures, thylakoids, the number of which is innumerable in a chloroplast. Thylakoids are held together in a granum. Chloroplast plays an important role in photosynthesis. Green coloured pigment called chlorophyll found in chloroplast. Its ground matter is called stroma.

Question 36.
Write a note on plastids.
Answer:
Plastids are present only in plant cells. They are of two types:
(1) Chromoplast (coloured plastid).
(2) Leucoplast (white and colourless plastid).
The plastid having green pigment is called chloroplast. It is essential for photosynthesis. Yellow and purple coloured pigments are also found in chloroplasts. Plastids also contain their own DNA and ribosomes.

Question 37.
Why does papaya look yellow, spinach look green and watermelon look red from inside ?
Answer:
Different pigments present in plants impart different colours in them. The pigment named carotene gives yellow colour to papaya, green pigment chlorophyll in spinach gives it green colour; xanthomycin pigment gives red colour to the inside of the watermelon. So, different colours found in plants are due to different pigments.

Question 38.
Write a note on vacuoles.
Answer:
Vacuoles are the storage sacs for solid or liquid materials. Vacuoles are small in size in animal cells whereas plant cells have larger vacuoles. In plant cell, vacuoles provide turgidity and rigidity to the cells. They play an important role in the disposal of waste products from the body.

Essay Type Questions

Question 1.
Explain the microscopic structure of an animal cell.
Answer:
Microscopic structure of an animal cell: The basic unit of life in living organism is called a cell. It is a small sized structure filled with protoplasm. The body of every animals is formed by grouping together of many cells. The shape ofthe cell varies and their number also varies (from organism to organism). Cell has two main parts:
(a) Cell membrane,
(b) Protoplasm.

(a) Cell membrane:
A cell is enclosed by a thin membrane which is made up of plasma. It is very thin, soft and smooth. Cell membrane is semi-permeable. It gives shape to the cell and protects the protoplasm in it. It controls the movement of material inside and outside the cell.

(b) Protoplasm:
All the material present inside the cell membrane constitutes protoplasm. In fact, protoplasm is the basis of life. All life activities are completed in the protoplasm. Protoplasm has two main parts:
(1) Nucleus,
(2) Cytoplasm.

1. Nucleus:
Every cell has a spherical structure in its centre known as nucleus. Nucleus controls all the activities of the cell. Nucleus has four main parts nuclear membrane, nucleoplasm, chromatin reticulum, nucleolus. Nucleus is enclosed by a double membrane which is attached to endoplasmic reticulum. Nucleus contains DNA, RNA and substance chromatin which is made up of proteins. Chromosomes are found on the thread-like structures which constitute chromatin. Chromosomes are composed of DNA and protein. Chromosomes carry the hereditary traits from parents to offspring through genes. In the centre of the nucleus is present a dense, dark straining organelle called nucleolus. It stores RNA in it and helps in cell division.

2. Cytoplasm: Protoplasmic material of the cell other than nucleus is called cytoplasm. It contains living as well as non-living particles.

Following cell organelles are present in the cytoplasm:

(i) Mitochondria: These are double membraned spherical or rod-shaped structures. Mitochondria contains DNA, RNA and respirator)’ enzymes. These are helpful in respiration. Mitochondria are also called energy houses or powerhouses of the cell.

(ii) Ribosomes: These are spherical structures composed of RNA and protein. They are found scattered freely throughout the cell cytoplasm in prokaryots. However, in eukaryotic cells they are found either in free state in the cytoplasm or attached on the outer surface membrane of RER.

(iii) Endoplasmic Reticulum:
It is a large network of membrane-bound tubules. ER communicates both with plasma-membrane as well as nuclear membrane. Ribosomes are found on its outer surface membrane (in case of RER). It is a network formed of proteins and lipids. It helps in the transport of materials within the cell. It establishes contact between cytoplasm and nucleus.

(iv) Golgibodies:
These are membrane-bound structures found near the nucleus. Its function is not so clear or distint, but it helps in the formation of cell wall and despatches the material synthesised in ER outside the cell.

(v) Centrosome:
It is a small spherical structure found near the nucleus. It contains one or two granules, the centrioles. It helps in cell division.

(vi) Lysosomes:
These are spherical or oval structures present inside the cell. They contain digestive enzymes. Lysosomes help in digestive activity and destruction of damaged cell organelles.

(vii) Vacuoles:
These are a few spherical or egg shaped regions in the cell where there is very little cytoplasm. These are called vacuoles. Vacuoles help in the disposal of poisonous material from the cell as well as in the storage of food particles. In some unicellular organisms, specialised vacuoles also help in expelling excess water outside the cell.

(viii) Cilia and Flagella:
These are some thin, hair-like structures which help in movement of the organism in a fluid medium. Cilia are more in number but smaller in size whereas flagella are one or two in number. Their length is comparatively more.

Question 2.
What is a nucleus ? Write its functions.
Answer:
Every cell has a nucleus present in the centre. It is spherical or oval-shaped. The cell which have more than one nucleus is called coenocyte.

Following are the main parts of a nucleus :
1. Nuclear membrane: It is a thin and elastic membrane which keeps the nucleus separate from the cytoplasm.
2. Nucleoplasm: The fluid present inside the nucleus is called nucleoplasm.
3. Nucleolus: It is present inside the nucleus and controls the synthesis of protein.
4. Chromosomes: Every nucleus contains thin and long structures called chromosomes. Chromosomes are composed of a substance called nucleoprotein. This substance is formed by the joining of nucleic acids and proteins. The number of chromosomes for one type‘of organisms is fixed.

Functions of Nucleus: Following are the functions of a nucleus:
(i) The main function of the nucleus is to control and coordinate the activities of the cell.
(ii) A cell cannot remain alive without a nucleus.
(iii) It controls the hereditary characters with the help of genes.

Question 3.
What are the main functions of:
(a) Plasma membrane
(b) Mitochondria
(c) Chromosomes
(d) Nucleolus
(e) Lysosomes
(f) Cell wall
(g) Ribosome
(h) Golgi apparatus
(j) Peroxisomes ?
Answer:
The main functions of each cell constituent are as follows :
(a) Plasma membrane: Being semi-permeable, it controls the movement of materials inside and outside the cell.
(b) Mitochondria: It is the powerhouse of the cell. It oxidises carbohydrates to produce energy.
(c) Chromosomes: They are the carriers of hereditary traits and DNA is present in them.
(d) Nucleolus: It synthesises ribosomes.
(e) Lysosomes: It functions as a digestive sac,/bag because it plays the role of intercellular digestion.
(f) Cell wall: It protects the internal contents of the cell.
(g) Ribosomes: These help in protein synthesis.
(h) Chloroplast: Its green pigment produces food during photosynthesis.
(i) Golgi apparatus: It forms lysosomes and peroxisomes.
(j) Peroxisomes: They are helpful in the oxidation reactions.

Practical Work

Experiment 1:
To observe osmosis with dried raisin.

Procedure:
(1) Take 3-4 dried raisins and put them in water. After 30 minutes observe them. Raisins swell because water enters them by osmosis.
(2) Place the swollen raisins in concentrated sugar solution and observe after half an hour. Raisins shrink because water in them moves to the solution because of osmosis.

Experiment 2:
To prepare a temporary slide of onion peel.

Procedure:
(1) Take onion peel from its concave side and place it in the watch glass containing water.
(2) Put a drop of water on a glass slide and with the help of a brush transfer the onion peel from the watch glass to the slide (on the drop of water) and put a drop of iodine and place a cover slip on it. Take care that there is no air bubble beneath the coverslip.
(3) Observe this under a compound microscope and make a diagram of the cells as per your observation.

Quick Review of the Chapter

1. Who coined the term ‘cell’?
(A) Robert Brown
(B) Robert Hooke
(C) M. Schielden
(D) Virchow
Answer:
(B) Robert Hooke

2. Which substance ¡s used by Robert Hooke in discovery of cell?
(A) membrane of an onion
(B) cork
(C) a leaf
(D) Toot of a plant
Answer:
(B) cork

3. Which scientist discovered living cells first of all?
(A) Robert Hooke
(B) Leeuwenhoek
(C) Virchow
(D) Robert Brown
Answer:
(B) Leeuwenhoek

4. Who discovered the nucleus of a cell?
(A) Purkinje
(B) Virchow
(C) Robert Brown
(D) Robert Hooke
Answer:
(C) Robert Brown

5. Who gave the name protoplasm to the living material inside the cell?
(A) Purkinje
(B) Robert Brown
(C) M. Schleiden
(D) Virchow
Answer:
(A) Purkinje

6. Who proposed ‘Cell Theory’?
(A) M. Schleiden
(B) T. Schwann
(C) Virchow
(D) both (A) and (B)
Answer:
(D) both (A) and (B)

7. …………… is not a unicellular organism.
(A) Amoeba
(B) Euglena
(C) Ferns
(D) Paramoecium
Answer:
(C) Ferns

8. When was electron microscope discovered?
(A) in 1936
(B) in 1940
(C) in 1942
(D) in 1944
Ans.
(B) in 1940

9. Which organelle is not found in all organisms?
(A) plasma membrane
(B) cell wall
(C) nucleus
(D) cytoplasm
Answer:
(B) cell wall

10. Which organelle allows in and out of materials and stops them?
(A) plasma membrane
(B) cytoplasm
(C) nuclei’s
(D) centrosome
Answer:
(A) plasma membrane

11. The process of osmosis is related to:
(A) plasma membrane
(B) cell wall
(C) selective permeable membrane
(D) nucleus membrane
Answer:
(C) selective permeable membrane

12. The use of osmosis process ¡s carried out in the plants as:
(A) absorption of water by roots
(B) exchange of gases in leaves
(C) intake of nutrition from outside environment
(D) all of the above
Answer:
(D) all of the above

13. Which is not a feature of plasma membrane?
(A) flexible
(B) formed of lipid, protein
(C) study possible under simple microscope
(D) absence of selective permeable feature
Answer:
(D) absence of selective permeable feature

14. Plant cell wall is composed of which substance?
(A) minerals
(B) fats
(C) cellulose
(D) glucose
Answer:
(C) cellulose

15. The longest cell of human body is:
(A) RBC
(B) WBC
(C) neuron cell
(D) skin cell
Answer:
(C) neuron cell

16. Which is non-living?
(A) plasma membrane
(B) cell wall
(C) golgibodies
(D) ribosome
Answer:
(B) cell wall

17. Which waste require to be excreted out by the cell?
(A) CO₂
(B) O
(C) water
(D) all of the above
Answer:
(A) CO₂

18. controls all functions of a cell.
(A) centrosome
(B) golgi apparatus
(C) nucleus
(D) chromosome
Answer:
(C) nucleus

19. Where are chromosomes found?
(A) in nucleus
(B) in nucleolus
(C) in protoplasm
(D) in cytoplasm
Answer:
(A) in nucleus

20. Hereditary characters are found in
(A) nucleus
(B) chromosome
(C) nucleolus
(D) mitochondria
Answer:
(B) chromosome

21. Which substance forms chromosome?
(A) DNA
(B) Protein
(C) fat
(D) both (A) and (B)
Answer:
(D) both (A) and (B)

22. The functional unit of a chromosome is called
(A) chioroplast
(B) chromosome
(C) gene
(D) lamella
Answer:
(C) gene

23. The feature of prokaryotic is not:
(A) small size
(B) nucleus present
(C) only one chromosome
(D) nucleus is not surrounded by nucleus membrane
Answer:
(B) nucleus present

24. The feature of eukaryotic ¡s not:
(A) small size
(B) nucleus region fully developed
(C) nucleus is found
(D) more than one chromosome
Answer:
(A) smaLl size

25. Ribosomes synthesise ………..
(A) fats
(B) proteins
(C) carbohydrates
(D) all three
Answer:
(B) proteins

26. What is formed by endoplasmic reticulum (ER)?
(A) respiratory system
(B) food synthesis system
(C) reticulum system
(D) all three
Answer:
(C) reticulum system

27. Which organelle detoxifies toxic substances and drugs in the liver cells?
(A) ER
(B) goigi apparatus
(C) lysosome
(D) vacuoles
Answer:
(A) ER

28. Which scientist told about Golgi apparatus first of all?
(A) Virchow
(B) Purkinje
(C) Camino
(D) T. Schwann
Answer:
(C) Camillo

29. Lysosome is formed by
(A) ER
(B) golgi apparatus
(C) vacuole
(D) mitochondria
Answer:
(B) Golgi apparatus

30. Which is not an organ of an animal cell? ‘
(A) plasma membrane
(B) cytoplasm
(C) vacuole
(D) cell wall
Answer:
(D) cell wall

31. How many m are there in ijtm?
(A) 106
(B)
(C) l0
(D) 106
Answer:
(A) l06

32. What is the name of system of disposal of waste of a cell?
(A) golgi apparatus
(B) vacuoles
(C) lysosome
(D) centrioles
Answer:
(C) lysosome

33. ………. is called a suicidal bag.
(A) golgi apparatus
(B) lysosome
(C) ER
(D) plastid
Answer:
(B) lysosome

34. ………….. is called powerhouse of a cell.
(A) centriole
(B) Golgi bodies
(C) mitochondria
(D) plastid
Answer:
(C) mitochondria

35. plays an important role in photosynthesis.
(A) m mitochondria
(B) ch chloroplast
(C) vacuole
(D) Golgi bodies
Answer:
(B) chloroplast

36. pigments are found in the chloroplast.
(A) green
(B) yellow
(C) pink
(D) all above mentioned
Answer:
(A) green

37. are storage sacs of solid or liquid substances.
(A) lysosome
(B) golgi apparatus
(C) vacuoles
(D) ER
Answer:
(C) vacuoles

38. In which ‚ear cell was discovered?
(A) 1565
(8) 1605
(C) 1600
(D) 1665
Answer:
(D) 1665

39. The fundamental organizational unit of life is:
(A) Chromoplasts
(B) Cell
(C) Leucoplasts
(D) Plasma
Answer:
(B) Cell

Haryana State Board HBSE 9th Class Science Important Questions Chapter 4 Structure of the Atom Important Questions and Answers.

Haryana Board 9th Class Science Important Questions Chapter 4 Structure of the Atom

Very Short-Answer Type Questions

Question 1.
How are materials formed?
Answer:
Materials are formed with the combination of atoms and molecules.

Question 2.
What is known as Atom?
Answer:
Atom is the microscopic indivisible particles that have an independent existence.

Question 3.
During which century did Dalton agree an atom to be indivisible?
Answer:
During 19th century, Dalton agreed an atom to be indivisible.

Question 4.
Which are the basic particles of an atom ?
Answer:
The basic particles of an atom are electrons, protons and neutrons.

Question 5.
Define isobars with examples.
Answer:
Atoms of different elements which have same mass number but different atomic numbers are known as isobars. For example, calcium (₂₀Ca⁴⁰) and argon (₁₈Ar⁴⁰) are isobars.

Question 6.
What is meant by electron ?
Answer:
In an atom, the negatively charged particle whose mass is \(\frac {1}{2000}\) part mass of a proton that revolves around the nucleus is called an electron.

Question 7.
Which scientist gets the honor of discovering electron?
Answer:
J.J. Thomson.

Question 8.
Which charge does remain on an electron?
Answer:
Negative (-ve) charge.

Question 9.
Which scientist discovered the canal Rays?
Answer:
The German scientist, E. Goldstein.

Question 10.
Which other name is called as the canal rays ?
Answer:
Canal rays are also called as positive rays.

Question 11.
Which electron are canal rays attracted towards in the electronic field ?
Answer:
Towards negative electron.

Question 12.
How are electron and proton represented ?
Answer:
Electron is represented by e~ and proton is represented by p+.

Question 13.
What is the mass and charge of proton ?
Answer:
The mass of proton is 1 unit and the charge is +1.

Question 14.
How much is the charge on an electron ?
Answer:
An electron has -1 charge.

Question 15.
Why is atom electrically neutral ?
Answer:
Because in an atom the number of electrons and protons mutually balance the charges.

Question 16.
Which discovery enabled J.J. Thomson to win the Nobel Prize in Physics ?
Answer:
For discovery of‘electron’.

Question 17.
When was J.J. Thomson born ?
Answer:
J.J. Thomson was born on 18 December, 1856.

Question 18.
What is the mass of‘alpha’ particles ?
Answer:
The mass of ‘alpha’ particles is 4u.

Question 19.
What are alpha particles?
Answer:
Alpha particles are binary-charged helium particles.

Question 20.
Which scientist is known as the father of nuclear physics?
Answer:
E. Rutherford is called as the father of nuclear physics.

Question 21.
When was E. Rutherford born?
Answer:
E. Rutherford was born on 30 August 1871.

Question 22.
According to Rutherford, where does the entire mass of an atom lie in ?
Answer:
In the micronucleus of the atom.

Question 23.
Compare the size of the nucleus with respect to that of the size of an atom.
Answer:
The size of the nucleus is 1O3 times less than that of the size of an atom.

Question 24.
Which charge does atom-nucleus have?
Answer:
Positive charge.

Question 25.
Of which element’s nucleus is known as proton?
Answer:
Of hydrogen nucleus.

Question 26.
What was the proposal of Neils Bohr regarding the revolving of electrons?
Answer:
According to Neils Bohr electrons revolve in a certain energy orbit.

Question 27.
According to Neils Bohr model, when an electron returns from a higher level orbit to a lower level orbit, then the difference of energy gets radiated into which form?
Answer:
Electromagnetic radiation or in the form of light.

Question 28.
Which particles does the nucleus of an atom have?
Answer:
Protons and Neutrons.

Question 29.
How many a maximum number of electrons can be accommodated in the first and second orbit of an atom?
Answer:
In the first orbit, two and in the second orbit, maximum of eight electrons can be accommodated.

Question 30.
Write down the name of the lightest atom.
Answer:
Hydrogen.

Question 31.
Write down the name of that atom which does not have any neutron.
Answer:
Protium (₁¹H ) which is an isotope of hydrogen.

Question 32.
Write down the number of proton and neutron present in the nucleus of helium.
Answer:
There are two protons and two neutrons in the nucleus of helium.

Question 33.
When and who discovered the neutron ?
Answer:
Chadwick discovered neutron in 1932.

Question 34.
In the structure of atom the electrons of which orbit determine the properties of atoms.
Answer:
The electrons in the last shell (valence shell).

Question 35.
In a single molecule of water, how many atoms of hydrogen and oxygen are there?
Answer:
In a single molecule of water, there are two atoms of hydrogen and one atom of oxygen.

Question 36.
Which atoms are chemically active?
Answer:
The atoms whose outermost shells are not complete are chemically active.

Question 37.
Which atoms are chemically neutral?
Answer:
Those atoms whose outermost shells are complete are chemically neutral. For example; helium and neon.

Question 38.
Give names of two bivalent atoms.
Answer:
(i) Calcium (Ca)
(ii) Berkelium (Be).

Question 39.
What is the valency of chlorine?
Answer:
One.

Question 40.
What will be the number of neutrons in the atom of the element whose atomic number is 19 and mass number is 39?
Answer:
Neutron = mass number – atomic number = 39 – 19 = 20

Question 41.
Why is the mass of the atom M and its ion M+ same?
Answer:
Because both have same number of neutrons and protons.

Question 42.
Write dow n two isotopes of uranium.
Answer:
²³⁵₉₂U and ²³⁸₉₂U

Question 43.
Which two of the following nuclei are isotopes mutually?
₉₀Z²³¹, ₉₁Z²³⁰, ₈₈Z²³⁰, ₉₀Z²³³
Answer:
₉₀Z²³¹ and ₉₀Z²³³

Question 44.
How many isotopes does carbon have ?
Answer:
Carbon has two isotopes 12 C and 14 C .

Question 45.
What are the atoms called that belong to only one element, which has same atomic number but different mass number?
Answer:
Isotopes.

Question 46.
What is the average mass of isotopes of chlorine?
Answer:
The average mass of isotopes of chlorine used to be 35.5u.

Question 47.
Which of the followings are nuclear isotopes?
₈₈Z²²⁶, ₈₇Z²³⁶,₈₈Z²³⁸,₈₈Z²³⁸
Answer:
₈₈Z²²⁶, ₈₈Z²³⁸,

Question 48.
Which radioactive isotope is used in the treatment of cancer ?
Answer:
Isotope of cobalt of mass number 60.

Question 49.
Which fuel is used in a nuclear plant ?
Answer:
In a nuclear plant, isotope of uranium (U-235) is used as fuel.

Question 50.
Which elements isotopes are used in treatment of goitre disease ?
Answer:
Isotopes of iodine are used in the treatment of goitre disease.

Question 51.
Write down names of two isobaric elements.
Answer:
Calcium and argon are isobaric elements.

Short-Answer Type Questions

Question 1.
Why are canal rays called as positive charged rays ?
Answer:
Falling of the canal rays towards negative electrons in the electric field shows that these rays are jointly made up of positively charged particles.

Question 2.
Write down the properties of canal rays.
Answer:
Following are the properties of canal rays:
(1) These rays move in a straight line.
(2) These rays are bent towards negative electrode in electric and magnetic field.
(3) They have mass many times more than the mass of electron.

Question 3.
Why are electrons called as planetary electrons in an atom ?
Answer:
In an atom, electrons revolve in their respective fixed large elliptical orbits just like planets in the sky revolve around the sun in their large elliptical orbits. Hence, electrons are called as planetary electrons.

Question 4.
Enunciate similarities and dissimilarities between protons and neutrons.
Answer:
Similarities between protons and neutrons:
(1) Mass of proton and neutron is approximately equal to a single atomic mass unit.
(2) Proton and neutron both exist in the nucleus of an atom.

Dissimilarities between protons and neutrons:
(1) Protons are positively charged particles, whereas neutrons are neutral particles.
(2) The mass of a neutron is somewhat more than that of the mass of a proton.

Question 5.
Write down the difference between electron and neutron.
Answer:
Following is the difference between electron and neutron.

Electron:
1. Electron possesses negative (-ve) charge.
2. They revolve around in different orbits outside the nucleus.
3. Their mass is the 1/2000th part by mass of a hydrogen atom.

Neutron:
1. Neutron possesses negligible charge.
2. They remain inside the nucleus.
3. Their mass is almost the same to that of the mass of an atom of hydrogen.

Question 6.
Write down the difference between electron and proton.
Answer:
Following is the difference between electron and proton :
Electron:
1. They possess unit (-ve) charge on them.
2. Their mass is l/’2000th part mass of an atom of hydrogen.
3. They revolve around in their respective orbits outside the nucleus.

Proton:
1. They possess unit (+ve) charge on them.
2. Their mass is almost the same to that of the mass of an atom of hydrogen.
3. They remain in the nucleus.

Question 7.
Explain the essential properties of the atomic nucleus.
Answer:
The essential properties of the atomic nucleus are as follows:
(1) The size of the atomic nucleus is 105 times smaller than the size of the atom itself i.e., its size is 10^-5A or 10^-15 m.
(2) Atomic nucleus is positively charged.
(3) Absolute mass of the atom remains to withstand into the nucleus.
(4) Most of the space around the atomic nucleus remains unoccupied.

Question 8.
Compare the properties of atomic nuclei and electron.
Answer:
The comparison of properties of atomic nucleus and electron is as follows:

Atomic Nucleus:
1. It possesses +ve charge on it.
2. It is situated in the central part.
3. Its mass is almost equal to that of the mass of the atom.

Electron:
1. It possesses (-ve) charge on it.
2. It revolves around the nucleus.
3. Its mass is l/2000th part mass of hydrogen atom.

Question 9.
What are the fundamental contributions of E. Rutherford to understand the structure of atom ?
Answer:
To understand the structure of atom, E. Rutherford gave a model of atom, according to which electrons were assumed revolving around the nucleus in their pre-planned orbits, it was just like as the planets in our solar system revolve around the sun in their fixed orbits. Besides, he told that the absolute mass of atom lies in its 4vely charged nucleus which is of the size 10^-15 m .

Question 10.
Is the number of electrons in different shells of an atom constant or inconstant ? Illustrate with examples.
Answer:
The number of electrons in different shells of an atom is constant. The distribution of electrons in different shells is done on the basis of Quantum Equation i.e., 2n²; where n indicates the serial number of the orbit like:

This distribution of electrons was conceived by Bohr and Bury. According to them, the valence shell (outermost shell) cannot accommodate more than eight electrons and second last shell cannot accommodate more than 18 electrons.

Example:
Hydrogen has only single orbit where only 1 electron is there. 2 electrons of helium revolve in the first orbit. Lithium has 3 electrons out of which the third electron enters the second shell. Similarly in the atom of calcium there are 20 electrons out of which in the first shell there are 2, in the second and third orbit 8-8 and in the fourth shell there are 2 electrons.

Question 11.
Define valency. How is it related to atomic structure?
Answer:
Valency:
Valency of an atom is the number of valence electrons, whereas valence electrons are the electrons of the valence shell of any atom. The valency of an element and the valency of the electrons present in its outermost shell have the following relationship :
(1) The elements that have 1-4 electrons in their valence shells, their valency is equal to that of the electrons present in the valence shell.

(2) The elements that have 5-8 electrons in their valence shells, their valency is equal to the (8-electrons existing) outermost shell of the element.

(3) In the valence shell of helium, due to two electrons, its outermost shell gets filled up completely, that is why the valency of helium is zero. Similarly, the valency of other active gases is zero because the outermost shells get accommodated.

Normally, valency of metals = number of electrons present in the outermost shell and valency of non-metals = 8- number of electrons present in the outermost shell. Therefore, we can say that valency is related to the atomic structure, since the valency of electrons present in the valence shell is known only by atomic structure.

Question 12.
What are valence electrons? How many valence electrons are there in Mg and Al ?
Answer:
Valence electrons present in the outermost orbit are known as valence electrons.
The atomic serial number of Mg and A1 is 12 and 13 respectively. Their electronic configuration is:
Mg – 2,8,2
Al – 2,8,3
Therefore, we come to know that the number of valence electrons in Mg and Al is 2 and 3 respectively.

Question 13.
Describe the distribution of electrons in different orbits of the following atoms : lithium, nitrogen, neon, magnesium and silicon.
Answer:

Question 14.
In the given hint ₂₀⁴⁰Ca , write down the mass number of calcium, atomic number, electronic configuration and atomic structure.
Answer:
Mass number = 40
Atomic number = 20
Electronic configuration = 2, 8, 8,2

Structure of nucleus :
Number of protons = 20
Number of neutrons = 40 – 20 = 20

Question 15.
How many of the following are protons and neutrons ?
¹⁴N₇ ¹⁴C₆ ¹⁵P₁₅
Answer:
(1) ¹⁴N₇
Atomic mass = 14
Atomic number = 7
Number of protons = 7
Number of neutrons = Atomic mass – atomic number = 14 – 7 = 7

(2) ¹⁴C₆
Atomic mass = 14
Atomic number = 6
Number of protons = 6
Number of neutrons = Atomic mass – atomic number
= 14 – 6 = 8

(3) ¹⁵P₁₅
Atomic mass = 31
Atomic number = 15
Number of protons = 15
Number of neutrons = Atomic mass – atomic number
= 31 – 15 = 16

Question 16.
Explain the chemical neutrality and chemical reactivity of atom.
Answer:
The chemical properties of an atom depend upon the schematic system of setting up of electrons in it. When the valence shell of an atom of an element gets filled up completely, then that element does not participate in chemical reaction, that is, such an atom is chemically neutral, for example neon, argon, etc. When the outermost shell of an atom of any element is not completely filled up, then such an atom is chemically reactive. The law of chemical reactivity depends upon the distribution system of electrons.

Question 17.
Why are inert or inactive gases behaviourally inactive?
Answer:
The valence shell in inert gases remains filled up completely. In helium, being the first orbit it gets completed due to two electrons. In rest of the inert gases it gets filled up with 8 electrons. Thereby, the electronic configuration of inert gases used to be stable. The cause of neutrality of these elements is the difficulty of entrance or exit of the electrons. It needs more energy to out electrons out of them more on so they also do not have the efficiency of acquiring electrons.

Question 18.
Boron has two isotopes ₅B¹⁰ (19%) and ₅B¹¹ (81%). Find average atomic weight for Boron.
Answer:
Average atomic mass of Boron atom = [10 x \(\frac {19}{100}\) + 11 x \(\frac {81}{100}\) ]
= \(\left[\frac{190}{100}+\frac{891}{100}\right]\) = [1.90 + 8.91] = 10.81 = 11

Essay Type Questions

Question 1.
Who discovered the nucleus of atom and how ?
Answer:
The nucleus of atom was discovered by Ernest Rutherford by experimenting with the scattering of alpha particles.

In this experiment, Rutherford happened to bombard a high speed stream of alpha particles on a thin foil of gold and he found that after striking the gold leaf, the alpha particles generally deflect from their path by an angle of 1°. One of the smallest parts of the alpha particles get scattered by a larger angular deflecting and come back after getting deflected very little.

It is a general fact that alpha particles are too much energetic particles. Their deflection of forming of bigger angle shows that they had hit against the total mass of atom of the substance. On the basis of this demonstration, he concluded that:

(i) The central part of the atom i. e., the nucleus is solid and has positive charge. The nucleus possesses approximately the total mass of the atom.
(ii) This central part of atom has a very’ small size as compared to the atom itself.

Question 2.
What new concept was introduced in Neils Bohr model of an atom by him ?
Answer:
Neils Bohr proposed a model of atom in 1912 A.D., which was basically based upon the new concept. These concepts are:

(1) Electrons revolve around the nucleus in fixed orbits and each orbit has a different radius.
(2) Each orbit does have its definite energy. Accordingly, the orbit located near the nucleus possesses the least energy and the orbit situated farthest from the nucleus possesses the maximum energy.
(3) When an electron moves to the orbit of a lower energy level from the higher energy level, then the difference of energy is emitted in the form of electromagnetic radiation or in the form of light.
(4) All around the nucleus to fill up the different orbits or shells the number of electrons does have a definite number.
(5) Electrons can constantly revolve in a stable orbit in the form of electromagnetic waves without radiating energy.
(6) If energy is propagated to the electron with a definite energy level, it can enter the orbit with a higher energy level.

Question 3.
What are the similarities in the electronic configuration of the following atoms?
(i) Lithium, Sodium, Potassium
(ii) Helium, Neon, Argon
(iii) Beryllium, Magnesium and Calcium.
Answer:
(i) Lithium, Sodium, Potassium:

In the above electron distribution, we learn that there is only one or single electron in the valence shell of all the three atoms of the elements i.e. Lithium, Sodium and Potassium due to that reason the valency of all these elements is the same.

(ii) Helium, Neon, and Argon:

From the above electron distribution, it is learned that the valence shells (outermost shells) of the atoms of all the three elements i.e., Helium, Neon and Argon are completely filled up, due to that reason their valency is zero or all these elements are inert or inactive.

(iii) Beryllium, Magnesium and Calcium:

From the above electron distribution we learn that in the atoms of all three elements, there are two electrons in the valence shell. Because of that reason, all the valency of all these elements is 2.

Question 4.
Explain with suitable examples the experimental uses of radioactive isotopes.
Answer:
Following are the experimental uses of radioactive isotopes :
(1) It can help in fixing the age of the earth, rocks, hills, meteors, etc.
(2) It can be used to find the thickness of paper, glass, plastic, etc.
(3) It can be used in finding out the cracks and crevices in the pipes.
(4) It helps in knowing the wear and tear in the machines.
(5) Isotopes are used in the treatment of different diseases in the medical field; e.g., CO-60 for curing cancer; isotope of iodine for curing thyroid, isotope of phosphorus for leukemia (blood cancer), etc.
(6) The radiations emitted through the radioactive isotopes are used in the form of high disease resistance in growing crops like wheat, paddy and groundnut (peanut).
(7) Isotopes are used in reforming fertilizers.
(8) Isotope Fe-59 is used to examine anemia

Question 5.
Show the electronic distribution of the first 20 elements in the Periodic Table.
Answer:
The electronic distribution of the first 20 elements in the periodic table is:

Practical Work

Experiment 1:
Prove experimentally that when two bodies are rubbed against each other, charge is produced.

Procedure:
(1) Take a comb and rub it against the dry hair. Bring the comb near to the paper-bits. We notice the comb attracts the paper-bits to it. This proves that on rubbing two bodies against each other, a charge gets produced.

(2) Rub a glass rod with a silken cloth on bringing this glass rod near to the balloon, the balloon will get attracted to the charged glass rod. Thus, the experiment proves that on rubbing the glass rod against the silken cloth, the glass rod gets charged.

Experiment 2:
Explain with an experiment Rutherford’s scattering of alpha (a) particles.

Procedure:
To understand Rutherford’s scattering alpha (a ) particles experiment is performed in the open ground. Suppose a child is standing in front of a wall with their eyes shut. Now, ask him to throw some stones against the wall from at a short distance. On striking every stone against the wall, he will hear a sound.

If he repeats the activity ten times, he will hear the sound ten times. But if the child with his eyes shut throws the stones against a wall surrounded with barbed wire, most of the stones will not strike against that boundary and hence, no sound will be heard. As there is enough blank space in between the boundary, through which the stone escapes.

Quick Review of the Chapter

1. Which scientist discovered Canal Rays ?
(A) Dalton
(B) Li. Thomson
(C) E. Goldstein
(D) Neils Bohr
Answer:
(C) E. Goldstein

2. Which scientist discovered electrons ?
(A) Thomson
(B) Dalton
(C) Goldstein
(D) Neils Bohr
Answer:
(A) Thomson

3. When was J.J. Thomson awarded Nobel Prize ?
(A) in 1878
(B) in 1902
(C) in 1906
(D) in 1912
Answer:
(C) in 1906

4. Which scientist proposed that an atom consists of positively charged sphere and the electrons are embedded in it ?
(A) Rutherford
(B) Thomson
(C) Dalton
(D) Neils Bohr
Answer:
(B) Thomson

5. E. Rutherford discovered
(A) atom
(B) nucleus
(C) proton
(D) neutron
Answer:
(B) nucleus

6. The radius of nucleus is times than the radius of an atom.
(A) 105
(B) 104
(C) 103
(D) 102
Answer:
(A) 105

7. Which scientist told that when electrons revolve in discrete orbits, then energy ?
(A) Neils Bohr
(B) Rutherford
(C) Dalton
(D) Thomson
Answer:
(A) Neils Bohr

8. Who is the author of the book ‘Atomic Theory’ ?
(A) Rutherford
(B) Thomson
(C) Neils Bohr
(D) both (A) and (B)
Answer:
(C) Neils Bohr

9. Charge on nucleus of an atom is:
(A) zero charge
(B) negative charge
(C) positive charge
(D) no charge
Answer:
(C) positive charge

10. When was neutron discovered?
(A) in 1902
(B) in 1912
(C) in 1922
(D) in 1932
Answer:
(D) in 1932

11. Who discovered neutron?
(A) J. Chadwick
(B) J ,J. Thomson
(C) Neil Bohr
(D) None of the above
Answer:
(A) J. Chadwick

12. The characteristic of electron is not:
(A) uncharged
(B) mass same as proton
(C) found in nucleus
(D) it has negative charge
Answer:
(D) it has negative charge

13. The characteristic of electron is not:
(A) positively charged
(B) represents by e-
(C) negatively charged
(D) lightest particle
Answer:
(A) positively charged

14. The characteristic of proton is not:
(A) found in nucleus
(B) represents by p+
(C) mass 1 unit
(D) negatively charged
Answer:
(D) negatively charged

15. The first electron shell of an atom can have maximum electrons.
(A) 2
(B) 8
(C) 18
(D) 32
Answer:
(A) 2

16. The maximum number of electrons in third electron shell can be:
(A) 8
(B) 12
(C) 18
(D) 32
Answer:
(C) 18

17. The number of electrons in fourth electron shell can be:
(A) 8
(B) 18
(C) 32
(D) 2
Answer:
(C) 32

18. What will be the atomic number of an element having 6 electrons in its M shell?
(A) 8
(B) 16
(C) 24
(D) 34
Answer:
(B) 16

19. The number of electrons present in outermost shell of neon:
(A) 2
(B) 8
(C) 18
(D) 32
Answer:
(B) 8

20. Which of the following element is inert gas?
(A) neoft
(B) argon
(C) cripton
(D) all of the above
Answer:
(D) all of the above

21. The number of electrons present in the outermost shell of fluorine
(A) 2
(B) 5
(C) 7
(D) 17
Answer:
(C) 7

22. The number of electrons in electrons in outermost shell can be:
(A) 2
(B) 8
(C) 18
(D) 32
Answer:
(B) 8

23. What is the number of neutrons in hydrogen
(A) zero
(B) one
(C) two
(D) four
Answer:
(A) zero

24. Protium is an isotope of which element ?
(A) helium
(B) hydrogen
(C) lithium
(D) nitrogen
Answer:
(B) hydrogen

25. The symbol of tritium is:
(A) ₁¹H
(B) ₁²H
(C) ₁³H
(D) ₁⁴H
Answer:
(C) ₁³H

26. Deuterium is an isotope of which element?
(A) uranium
(B) lithium
(C) helium
(D) hydrogen
Answer:
(D) hydrogen

27. …………. is used as fuel in atomic furnace.
(A) Lithium
(B) Helium
(C) Uranium
(D) Beryllium
Answer:
(C) Uranium

28. The isotope of which element is used in the treatment of cancer ?
(A) Cobalt
(B) Iodine
(C) Boron
(D) Chlorine
Answer:
(A) Cobalt

29. the isotope of iodine is used in the treatment of ……………. disease
(A) atomic nucleus
(B) electron
(C) proton
(D) neutron
Answer:
(A) atomic nucleus

30. If K and L shell of an atom are full, then the number of electrons in it will be:
(A) 16
(B) 8
(C) 17
(D) 18
Answer:
(D) 18

31. For Which invection is Rutherfords alpha scattering experement responsible?
(A) atomic nucleus
(B) electron
(C) proton
(D) neutron
Answer:
(A) atomic nucleus

32. The number of electrons in Cl^– ion is:
(A) 16
(B) 8
(C) 17
(D) 18
Answer:
(D) 18

33. Which is correct electronic configuration of sodium ?
(A) 2, 8
(B) 8, 2, 1
(C) 2,8,1
(D) 8,2
Answer:
(C) 2, 8, 1

34. The fundamental particle of an atom is not:
(A) electron
(B) positron
(C) proton
(D) neutron
Answer:
(B) positron

35. Which one of the following is a correct electronic configuration of chlorine?
(A) 2, 7, 8
(B) 2, 8, 7
(C) 7, 8, 2
(D) 1, 8, 8
Answer:
(B) 2, 8, 7

Haryana State Board HBSE 9th Class Science Important Questions Chapter 3 Atoms and Molecules Important Questions and Answers.

Haryana Board 9th Class Science Important Questions Chapter 3 Atoms and Molecules

Very Short-Answer Type Questions

Question 1.
Which two laws did the scientist Antonie L. Lavoisier establish who laid the foundation of chemical sciences?
Answer:
(1) Law of Conservation of Mass.
(2) Law of Constant Proportions.

Question 2.
What is the law of conservation of mass?
Answer:
According to the law of conservation of mass, during the chemical reaction mass is neither created nor destroyed.

Question 3.
What is the law of constant/definite proportions?
Answer:
According to the law of constant/definite proportions, in pure chemical matter, element always exist in definite proportions by mass.

Question 4.
in accordance with mass in ammonia (NH₃), what is the ratio of nitrogen and hydrogen ?
Answer:
According to mass in ammonia (NH₃), the ratio of nitrogen and hydrogen is 14:3.

Question 5.
In water (H₂O), according to mass what is the ratio of hydrogen and oxygen ?
Answer:
In water (H₂O), according to mass the ratio of hydrogen and oxygen is 1 : 8.

Question 6.
What is an atom ?
Answer:
Atom is that smallest particle of an element, in which all the chemical properties of that element are present and it also maintains those properties.

Question 7.
Which principle did John Dalton introduce regarding the nature of matter ?
Answer:
According to John Dalton, all the matter, whether element, compound or mixture are formed of small particles, which are called atoms.

Question 8.
Which are the basic particles of atom ? .
Answer:
The basic particles of atom are proton, neutron and electron.

Question 9.
Which microscope is used to catch the photograph of atom ?
Answer:
To catch the photograph of atoms Scanning Tunneling Microscope (STM) is used.

Question 10.
Define a molecule.
Answer:
A molecule is that smallest particle of an element or a compound which has its individual or independent existence and it displays all the properties of that substance (element or compound).

Question 11.
Write down the names and symbols of any two monoatomic molecules.
Answer:
Argon (Ar) and Helium (He). –

Question 12.
Write down the formulae of two diatomic and tetra-atomic molecules.
Answer:
Diatomic molecules – H₂, N₂, HCl
Tetra-atomic molecules – H₂O, CO₂

Question 13.
What is meant by poly-atomic molecules ?
Answer:
The molecules that have more than four atoms, are called poly-atomic molecules like Sg and C2HsOH.

Question 14.
What information does a molecular formula of a substance provides us ?
Answer:
The molecular formula of a substance tells us that how many atoms of every type coexist in its single molecule.

Question 15.
What is the relationship between nanometre and metre ?
Answer:
1 nanometre (nm) = 10^-9 metre (m).

Question 16.
What is measure unit to measure atomic radius?
Answer:
Atomic radius is measured in nanometre (nm).

Question 17.
What is the atomic radius of hydrogen?
Answer:
The atomic radius of hydrogen is 10^-10 metre.

Question 18.
What does the abbreviation IUPAC stand for?
Answer:
IUPAC means International Union of Pure and Applied Chemistry.

Question 19.
What is the symbol of iron and where does it originate from?
Answer:
The symbol of iron is Fe which originates from its Latin name Ferrum.

Question 20.
Which are the Latin names from where the symbols of sodium and potassium originated ?
Answer:
The symbols of sodium (Na) and potassium (K) originated from the Latin names Natrium and Kalium respectively.

Question 21.
What is the difference between N₂ and 2N ?
Answer:
N₂ is a molecule of nitrogen, whereas 2N are two atoms of nitrogen. .

Question 22.
What is meant by structural formula ?
Answer:
Structural formula is a chemical formula that shows how do atoms in a molecule remain united on combined.

Question 23.
What is the structural formula of water ?
Answer:
The structural formula of water is H-O-H.

Question 24.
What is the formula of carbon monoxide ?
Answer:
The formula of carbon monoxide is CO.

Question 25.
Define atomic mass unit (a m u).
Answer:
Atomic mass unit (a m u) is defined w.r.t. \(\frac {1}{2}\) part mass of atom of a particular isotope of carbon (C-12).

Question 26.
What is meant by molecular mass ?
Answer:
The molecular mass of a substance is the sum total of atomic mass of all the atoms existing in the one molecule of that substance.

Question 27.
What is meant by mass formula ?
Answer:
The mass formula of a substance is the sum total of atomic mass of the entire atoms existing in the formula unit of that compound, whether
it is a molecule or not, it doesn’t concern.

Question 28.
What is the molecular mass of CH₃OH ?
Answer:
The molecular mass of CH₃OH = (12 + 3 × 1 + 16 + 1)u = (12 + 3 + 16 + 1) u = 32u

Question 29.
What is the numerical unit of atoms and molecules?
Answer:
The numerical unit of atoms and molecules is mole.

Question 30.
Which micro-particles combine to form molecules?
Answer:
Atoms.

Question 31.
Who provided information about atom and when?
Answer:
John Dalton in 1808 A.D. ‘

Question 32.
What is called as writing of an element in short form?
Answer:
Symbol.

Question 33.
What is the symbol of copper ?
Answer:
Cu.

Question 34.
What is the symbol of aluminium ?
Answer:
Al.

Question 35.
Write down the symbols of gold and silver.
Answer:
Gold = An, Silver = Ag

Question 36.
What is meant by chemical formula ?
Answer:
Representation of structure of a molecule of a compound through chemical symbols is called chemical formula.

Question 37.
What is meant by atomicity ?
Answer:
Number of atoms present in a molecule of an element is called its atomicity.

Question 38.
What is the atomicity of inert gases?
Answer:
One.

Question 39.
Write the name of a triatonic atom.
Answer:
Ozone (O₃).

Question 40.
What are the molecules possessing two atoms called ?
Answer:
Diatomic.

Question 41.
What is the atomicity of phosphorus and sulphur ?
Answer:
The atomicity of Phosphorus is four and that of sulphur is eight.

Question 42.
Give the chemical formula of copper chloride.
Answer:
CuCl₂.

Question 43.
What is meant by chemical equation ?
Answer:
The symbolic representation of a chemical reaction is known as chemical equation.

Question 44.
What is mole ?
Answer:
Mole is the quantity of matter in which 12 g of C-12 the number of molecules (atoms, molecules or ions) that have an equal number of atoms.

Question 45.
What is Avogadro’s Constant?
Answer:
Avogadro’s constant (6.022 × 10²³ mol^-1) is defined as the number of atoms present in 12 grams of 12 C.

Question 46.
Define molar mass.
Answer:
The mass of one-mole molecules of a substance is called as molar mass.

Question 47.
What is the symbol and unit of molar mass?
Answer:
Symbol: M.
Unit: g/mol or Gram per mole.

Question 48.
Give the molar mass of water and oxygen.
Answer:
M(H₂O) = 18 g/mol
M (O₂) = 32 g/mol.

Question 49.
What are charged particles called?
Answer:
Charged particles are called ions.

Question 50.
What is meant by anion and cation?
Answer:
Negatively charged particles are called as anions and positively charged particles are called cations.

Short-Answer Type Questions

Question 1.
Discuss the basic principle introduced by John Dalton regarding the nature of matter.
Answer:
The basic principle introduced by John Dalton regarding the nature of matter states that all substances whether they are elements, compounds or mixtures are composed of minute particles called atoms. It can be discussed as follows:
(1) Element is composed of very tiny indivisible particles, which are called atoms.
(2) All the atomic masses and characteristics or properties of a given element are equal in both. Atoms
of different elements have different masses and properties.
(3) The creation and destruction of atoms of an element cannot be transformed into atoms of other element.
(4) When atoms of different elements combine themselves in smaller but complete ratio, then they form compounds.
(5) In the given compound the relative number and kinds of atoms remain constant.
In brief, atom is the smallest particle of an element that keeps its chemical identity in all chemical and physical changes. The atoms of an element are different from the atoms of other elements.

Question 2.
How is modern concept different from that of the Daltons principle in terms of atom ?
Answer:
According to Daltons opinion, atom is the smallest and indivisible particle of matter and atom can neither be created nor destroyed, but according to the modem concept an atom can be further divided into even more smaller particles – electrons, protons and neutrons. Nowadays, by splitting the nucleus of atom, atom bomb is made, which expresses the difference from the law of indestructibility of atom.

Question 3.
What were the drawbacks found in the principle of Dalton ? Clarify with examples.
Answer:
Daltons principle could not explain some of the facts, which are as follows:
(1) Diamond and Graphite are formed of the same element, even then why is there so much difference in their properties ? Diamond is the hardest and the brightest thing found in nature and graphite on the other hand, is soft and of black colour.
(2) According to the principle of atom, atom is an indivisible particle, but according to the modem discoveries; atom is formed of protons, electrons and neutrons in a combined way.
(3) Mass of two atoms of an element can also be different like uranium has two isotopes ₉₂U²³⁵ and ₉₂U²³⁸whose atomic mass is 235u and 238u respectively.

Question 4.
Explain that atom is divisible rather than indivisible.
Answer:
A comprehensive study has proved that atoms of certain elements release radiations that are capable to penetrate through many substances like paper. The emission of radiations or particles from atoms proves this thing that atoms are not indivisible but, divisible.

Question 5.
How big are atoms in size?
Answer:
Atoms are very small. They are even smaller than a thing that we can imagine or compare. When millions of atoms are stacked, then it would hardly form a thick layer same as thick that of a sheet of paper.

Question 6.
Show the radii of the following substances in metres:
(1) Atom of hydrogen
(2) Molecule of water
(3) Molecule of haemoglobin
(4) Grain of sand.
Answer:

Question 7.
Fill in the blanks:
(1) Element is composed of only one type of
(2) In a hydrogen molecule, the number of hydrogen atoms are
(3) A compound is formed of with the combination of at least elements.
Answer:
(1) atoms
(2) two
(3) two.

Question 8.
Write down the symbols of the following elements : aluminium, calcium, cobalt, iodine and mercury.
Answer:

Question 9.
Which elements do the following symbols represent ? Na, K, P, Pb, Ca, Zn, Br and Sn.
Answer:

Question 10.
Match the statements given in Column A with the symbols given in Column B:

Answer:

Question 11.
On the basis of Latin names, write down names and symbol of some elements.
Answer:

Question 12.
Write down the names of the elements present in the following compounds:
Calcium Oxide (CaO), sulphur dioxide (SO₂), potassium nitrate (KNO₃), mercuric oxide (HgO) and borax (Na₂B₄O₇).
Answer:
Elements present in the given compounds are shown in the following chart:

Question 13.
Why da we not take 1/6 part of the mass of oxygen atom in the form of a unit ?
Answer:
We do not take 1/6 part of the mass of oxygen atom in the form of a unit because:
(1) Oxygen forms compound after reacting with many other elements.
(2) With this atomic mass unit, the atomic masses of most of the elements are obtained in maximum number.

Question 14.
How do atoms remain in existence ?
Answer:
Atoms of most of the elements cannot remain in existence in independent state. Atoms form molecules and ions. These molecules or ions combine together in a huge number to form a fluid which we can see, feel or touch.

Question 15.
Show the following compounds by means of molecular models:
(i) Water
(ii) ammonia
(iii) ethyl alcohol
(iv) chlorine
(v) phosphorus
(vi) sulphur.
Answer:
The molecular models of the given simple compounds are as follows:

Question 16.
Give the difference between the following :
(i) Hydrogen atoms and its molecules.
(ii) Molecules of oxygen and molecules of water.
(iii) Molecules of sugar and molecules of water.
(iv) Molecules of calcium oxide and molecules of magnesium oxide.
Answer:
(i) The smallest unit of hydrogen (H), is the atom of hydrogen, but a molecule of hydrogen is formed of with the combination of two atoms (H₂).
(ii) A molecule of oxygen consists of two atoms of oxygen (O₂), but in a molecule of water there are two atoms of hydrogen and a single atom of oxygen (H₂O).
(iii) A single molecule of sugar consists of 12 atoms of carbon, 22 atoms of hydrogen and 11 atoms of oxygen (C₁₂H₂₂O₁₁), but a single molecule of water consists of two atoms of hydrogen and one atom of oxygen (H₂O).
(iv) A single molecule of calcium oxide consists of one atom of calcium and one atom of oxygen (CaO), but in a single molecule of magnesium oxide consists of one atom of magnesium and one atom of oxygen (MgO).

Question 17.
Write down the names of the elements present in the following compounds and also give the number of atoms present in the atoms:
Baking Soda (NaHCO₃), Sodium Carbonate (Na₂CO₃), Copper Sulphate (CuSO₂), Sand (SiO₂), Aluminium Chloride (AlCl₃):
Answer:
The names of the elements present in the given compounds and the number of atoms present in each element is given in the table as given ahead:

Question 18.
What is meant by monoatomic, diatomic and polyatomic?
Answer:
Monoatomic: Elements that are found in the form of single atom are called monoatomic. For example, Helium (He) and Neon (Ne).
2. Diatomic: Those elements that have two atoms in a single molecule, are called diatomic. For
example, Hydrogen (H₂), Oxygen (O₂), and Nitrogen (N₂).
3. Polyatomic: The elements that consist of more than two atoms in their single molecule are called
polyatomic. For example, Phosphorus (P₄) , and Sulphur (S₉).

Question 19.
What is meant by atomicity? Write down formulae and atomlcity 01 some elements.
Answer:
The number of atoms present in a molecule of an element is called its atomicity. The formulae and atomicity of some elements is as follows:

Question 20.
What things should be kept in mind while writing a chemical formula of a compound ?
Answer:
While writing a chemical formula of a compound, following things should be kept in mind:
(1) The valency or change of ion should be balanced.
(2) When a compound is made up of any metal or non-metal, then the name of the metal or its symbol is written in chemical formula before. For example, Calcium Oxide (CaO), Sodium Chloride (NaCl), Iron Sulphide (FeS), Copper Oxide (CuO), etc. where oxygen, chlorine, sulphur are non-metals and they are written on right hand side, whereas calcium, sodium, iron and copper are metals and they are written on left nand side.
(3) In compounds composed of polyatomic ions, ions are put into brackets first, after that the number showing the proportionalities is written.

Question 21.
The chemical formula of water is H₂O. What information do we get from it ?
Answer:
We get the following information from the chemical formula of water H₂O:
(1) We come to know from the chemical formula that the given compound H20 is formed of the combination of hydrogen and oxygen.
(2) Also, we come to know about the number of atoms of each element present in the single molecule of a substance through the chemical formula i.e., there are two atoms of hydrogen and one atom of oxygen in H₂O.
(3) Through chemical formula, the valency of each element present in a given substance is understood or in H₂O, the valency of oxygen is 2 and that of hydrogen is 1.
(4) Through chemical formula, we come to know the molecular mass of the given substance i.e., the molecular mass of H₂O is 1 x 2 + 16 = 18 u.
(5) Through chemical formula we come to know that what the proportion of the number of atoms of
the components of elements is and the ratio from the point of view of mass in the given substance. i’. e., in H₂O, H: O = 2 : 1 and from the point of view of mass H : O = 2 : 16 or = l : 8.
(6) The chemical formula shows that the given compound is electrically neutral i. e. H₂O does not possess any charge on it.

Question 22.
How is molecular mass or molecular weight calculated with the help of formula?
Answer:
In the following way the molecular mass or molecular weight is calculated :
(1) First of all write down the chemical formula of the compound.
(2) Now write down each element separately.
(3) Then write down the number of atoms of all elements.
(4) Thereafter, write down the atomic mass of the elements.
(5) Now, multiple the number of atoms of the elements with their atomic masses.
(6) Now add all the products. This is the real mass of the compound.
For Example:

Question 23.
How many moles of chlorine atom are there in each mole of the following compounds?
(a) Cl₂O₇
(b) HCl
(e) BaCl₂
(d) AlCl₃
(e) FeCl₃
(f) CCl₄
Solution:

Question 24.
How is the mass percentage of element Aand element B in the given compound AB calculated?
Answer:
AB is a compound whose one element is A and the other element is B. We give the mass percentage of A in terms of AB of its one hundred parts in the form of division of A.

Numerical Questions

Question 1.
Calculate the molecular mass of the following compounds:
(i) NH₃
(ii) NaCl
(iii) (NH₄)₂ SO₄
(iv) Al₂ (SO₄)₃
(v) C₆H₁₂O₆
(vi) CaCO₃
[N = 14, H 1, Na 23, Cl = 35.5, S = 32,0 16, Al = 27, C = 12, Ca = 401]
Solution:
(1) Molecular mass of NH₃ = [14 + 3 × 1] u
= [14 + 3]u
= 17u

(ii) Molecular mass of NaCI = [23 + 35.5] u = 58.5 u

(iii) Molecular mass of (NH₄)₂ SO₄ = [2(14 + 4 × 1) + 32 + 4 × 16] u
= [2(18) + 32 + 64]u
= [36 + 32 + 64]u
= 132u

(iv) Molecular mass of A12(S04)3 = [2 × 27 + 3 (32 +4 × 16)] u
= [54 + 3(32 + 64)lu
= [54 + 3(96)]u
= [54 + 288]u
= 342u

(v) Molecular mass of C₆H₁₂O₆ [6 × 12 + 12 × + 6 × 16] u = [72 + 12 + 96] u = 180u

(vi) Molecular mass of CaCO3 [40 + 12 + 3 x 16] u
= j40+12+48]u
= 100 u

Question 2.
Find number of molecules in the following:
(i) 0.25 mole of oxygen gas
(ii) 66 g carbon dioxide
Solution:

(i) Number of molecules in I mole oxygen = 6.022 × 10²³ molecules
∴ Number of molecules in 0.25 mole oxygen = 6.022 × 10²³ × 0.25 molecules = 1.505 × 10²³ molecules

(ii) We know that I mole carbon dioxide (CO₂) = = (1 × 12 + 2 × 16]g = (12 + 32)g = 44g
Number of molecules in 44g carbon dioxide = 6.022 × 10²³ molecules
∴ Number of molecules in 66g carbon dioxide = \(\frac{6.022 \times 10^{23}}{44}\) × 66 molecules
= 9.033 × 10²³ molecules

Question 3.
How many atoms of iron will be there in the piece of iron (Fe) with 2.8 gram mass ?(Fe = 56g)
Solution:
One mole of atoms of iron = 6.022 × 10²³ atom = 56g
Number of atoms in 56 g of iron = 6.022 × 1o²³
Number of atoms in 2.8 g of iron = \(\frac{6.022 \times 10^{23}}{56}\) × 2.8 = 3.011 × 10²² atoms

Question 4.
Calculate the mass of the following in grams:
(a) One mole of sulphuric acid (H₂SO₄),
(b) 0.5 mole of aluminium sulphate (Al₂(SO₄)₃).
Solution:
(a) Mass of one mole of H₂SO₄ in grams = 1 × 2 +32 + 16 × 4
= 2 + 32 + 64
= 98g

(b) Mass of one mole of Al2 (SO4)3 in grams = 27 × 2 + 3(32 + 16 × 4)
= 54 + 3(32 + 64)
= 54 + 3 × 96
= 54 + 288 = 342g
= 54 + 288 = 342g
∴ Mass of 0.5 mole of Al₂(SO₄)₃ in grams = 342 × 0.5
= 342 × \(\frac {5}{10}\) = 171 g

Question 5.
Calculate the number of moles of CaCO₃ of 20 g of calcium carbonate (CaCO₃).
Solution:
Onemole of CaCO₃ = 40 × 1 + 12 × 1 + 16 × 3
= 40 + 12 + 48
= 100g

Question 6.
In aluminium sulphate Al₂(SO₄)₃ of 34.2 g salt, how many moles of each element will be there?
Solution:
One mole of Al₂(SO₄)₃ = 2 × 27 + 3 × 32 + 12 × 16 = 54 + 96 + 192 = 342g
(1) Number of Al moles in 342 g of Al₂ (SO₄)₃= 2 mole
∴ Number of Al moles in 34.2 g of Al₂ (SO₄)₃ = \(\frac{2}{342}\) × 34.2 = 0.2 mole

(2) Number of S moles in 342 g of Al₂ (SO₄)₃ = 3 mole
∴Number of S moles in 34.2 g of Al₂ (SO₄)₂ = \(\frac{3}{342}\) × 34.2 = 0.3 mole

(3) Number of O moles in 342 g of Al₂ (SO₄)₃ = 12 mole
∴Number of O moles in 34.2 g of Al₂ (SO₄)₃ = \(\frac{12}{342}\) × 342 = 1.2 mole

Question 7.
How many molecules of water are there in 1 g of H₂O?
Solution:
I mole of H₂O = 1 × 2 + 16 × 1
= 2 + 1618g
∴Molecules in 18 g (one mole) H₂O = 6.022 × 10²³
Molecules in 1 g H₂O = \(\frac{6.022 \times 10^{23}}{18}\)
= 3.346 × 10²²

Question 8.
Convert the following into moles:
(i) 3.012 x 10²³ Sodium atoms
(ii) 180 g water
Solution:
(i) 6.022 × 10²³ Sodium atoms 1 mole sodium
∴3.0 12 × 10²³ Sodium atoms = 6.022x 10²³ × 3.012 × 10²³ mole sodium

(ii) We know that 1 mole water (H₂O) (2 × 1 + 1 × 16] g = 2 + 16 = 18g
∵ 18 g water = 1 mole water
∴180 g water = \(\frac {1}{18}\) × 180 mole water = 10 mole water

Question 9.
Determine the mass of 6.022 × 10²³ N₂ molecules.
Solution:
1 mole N₂ = 2 × 14 = 28g
= 6.022 × 10²³ molecules
∴Mass of molecules 6.022 x 10²³ molecules N₂ = 28g

Question 10.
Calculate the molar mass of the following and write down their suitable standard units.
C₂H₅OH, S₈, PCl₅
Solution:
We know that mass of one mole of a substance is called as its molar mass.
(i) Molar mass of C₂H₅OH = (2 x 12 + 5 × 1 + 16 + 1)g/mol
= (24 + 5 + 16 + 1) g/mol = 46 g/mol

(ii) Molar mass of S₈ = (8 x 32 = 256) g/mol
(iii) Molar mass of PCl₅ = (3 1 + 5 × 35.5) g/mol = (3 1 + 177.5) g/mol
= 208.5g/mol

Question 11.
Calculate the number of particles in 0.1 mole carbon atom.
Solution:
1 mole carbon = 6.022 × 10²³ particles
0.1 mole carbon = 0.1 × 6.022 × 10²³ particles = 6.022 × 10²² particles

Question 12.
Calculate the molecular mass of the following:
(i) PCl₅
(ii) NH₃
(iii) CH₂ Cl₂
(iv) H₂O₂
(v) S₈
(vi) HCl
Where-P=31, Cl=35.5, N=14, H=1, Cl₂, O₁₆, S=32
Solution:
(i) Molecular mass of PCl₅ = [31 + 5 x 35.5] u = [31 + 177.5] u = 208.5 u
(ii) Molecular mass of NH₃ = [14 + 3 × l]u = 17u
(iii) Molecular mass of CH₂Cl₂ = [12 + 2 × 1 + 2 × 35.5] u = [12 + 2 + 71]u = 8Su
(iv) Molecular mass Of H₂O₂ = [2 x 1 + 216]u = [2 + 32] u = 34u
(v) Molecular mass of S₈ = 8 x 32u = 256u
(vi) Molecular mass of HCl = [1 + 35.5] u = 36.5 u

Question 13.
Calculate the mass formula of the following compounds:
(i) MgO
(ii) CaCl₂
(iii) CaCO₃
(iv) MCl₃
Solution:
(i) Mass formula of MgO = [24 + 16] g = 40 g
(ii) Mass formula of CaCl₂ = [40 + 2 x 35.5] g = [40 + 71]g = lllg
(iii) Mass formula of CaCO₃ = [40 + 12 + 3 x 16] g = [40 + 12 + 48] g = 100 g
(iv) Mass formula of Al Cl₃ = [27 + 3 x 35.5] g = 127 + 106.51g = 133.5g

Question 14.
Calculate the percentage of each element in I mole formaldehyde (CH₂O).
Solution:
Molar mass of CH₂O [12 + 2 x 1 + 16] g/mol = 3Ogfmol
Percentage of C in CH₂O = \(\frac {π}{2}\) x 100 = 40%
Percentage of H in CH₂O = \(\frac{2 \times 1}{30}\) x 100 = 6.7%
Percentage of O in CH₂O = \(\frac{16}{30}\) x 100 = 53.3%

Question 15.
How many atoms of each element are there in 6.3 g of nitric acid (HNO3)?
Solution:
Molecular mass of HNO₃ = 1 x 1 + 14 x 1 + 16 x 3 = 1 + 14 + 48 = 63 u
Mass of I mole of HNO₃ = 63 g
63g HNO₃ = 1 mole
∴63g HNO₃ = \(\frac{1 \times 6.3}{63}\) mole = 0.1 mole
(1) Number of H-atoms in I mole HNO₃ = 1 mole H – atoms
= 6.022 x 10²³ H-atoms (Avogadro’s number)
∴Number of H-atoms in 0.1 mole HNO₃ = \(\frac{6.022 \times 10^{23} \times 0.1}{1}\)
= 6.022 x 10²³ H-atoms

(2) Number of N-atoms in I mole HNO₃ = 1 mole N-atoms
= 6.022 x 10²³ N-atoms
∴Number of N-atoms in 0.1 mole HNO₃ = \(\frac{6.022 \times 10^{23} \times 0.1}{1}\)
= 6.022 x 10²² N-atoms

(3) Number of 0-atoms in I mole HNO₃ = 3 mole 0-atoms
= 3 x 6.022 x 10²³ 0-atoms
= 18.066 x 10²² 0-atoms
Number of 0-atoms in 0.1 mole HNO₃ = \(\frac{6.022 \times 10^{23} \times 0.1}{1}\)
18.066 x 1o 0-atoms Ans

Question 16.
Calculate number of chloride ions in 9.Sg of magnesium chloride.
(Atomic mass: Mg = 24, Cl = 35.5)
Solution:
1 mole of magnesium chloride (MECl₂) = mass of Mg + mass of Cl x 2 = 24 + 35.5 x 2 = 24 + 71 = 95g
∵ 95g Magnesium Chloride = 1 mole
∴ 9.5g Magnesium Chloride = \(\frac {1}{95}\) x 9.5 mole = 0.1 mole
∵ 1 moIe Magnesium Chloride = 2 x 6.022 x 10²³ Chloride ions
∴ 0.1 mole Magnesium Chloride = 0.1 x 2 x 6.022 x 10²³ Chloride ions
= 1.2044 x 10²³ Chloide ions

Question 17.
Calculate Molecular mass of the following compounds.
Na₂SO₄, ZnCO₃, CaSO₄, H₂SO₃, HNO₂ and N₂O₅
(Atomic Mass): (Na 23.04, S = 32.04, 0 = 16.04, Zn = 65.04, C = 12.04, Ca = 40.04, 11 = 1.04, N= 14.04)
Answer:
(i) Molecular mass of Na₂SO₄ = [2 x 23 + 1 x 32 + 4 x 16] u = [46 + 32 + 64]u = 142u
(ii) Molecular mass of ZnCO₃ [1 x 65 + 1 x 12 + 3 x 16] u = [65 + 12 + 48]u = 125u
(iii) Molecular mass of CaSO₄ = [1 x 40 + 1 x 32 + 4 x 16] u = [40+ 32+ 64] u = 136u
(iv) Molecular mass of H₂SO₃ = [2 x 1 + 1 x 32 + 3 x 16]u = [2 + 32 + 48]u = 82u
(v) Molecular mass ofHNO₂ = [1 x 1 + 1 x 14 + 2 x 16]u = [1 + 14 + 32]u = 47u
(vi) Molecular mass of N₂O₅ = [2 x 14 + 5 x 16] u = [28 + 80] u = 108u

Do Yourself

Question 1.
Calculate the number of moles in the following:
(i) 52g helium (get mole from mass).
(ii) 5.6g Fe
Answer:
(i) 13 mole
(ii) 0.1 mole.

Question 2.
Non-gas has single atoms. In how much rass of neon will there be 6.022 x 10²³ atoms?
Answer:
20g

Question 3.
(i) In 9 g water
(ii) In 17 g ammonia how many molecules will be present?
Answer:
(i) 3.011 x molecules
(ii) 6.022 x 10²³ molecules.

Question 4.
Find out the number of moles in 17g H₂O₂
Answer:
0.5 mole.

Question 5.
Calculate the masses of the follòwing:
(i) 0.5 mole N₂ gas (mass from the mole of molecule).
(ii) 0.5 mole N atoms (mass from the mole of atom).
(iii) 3.011 x 10²³N number of atoms (mass from number).
Answer:
(i) 142
(ii) 72
(iii) 72.

Question 6.
Calculate the molar mass of the following substances:
(i) Ethyne (C₂H₂)
(ii) Molecular Sulphur (S₈)
(iii) Phosphorus molecule (P)
(iv) Hydrochloric acid (HCl)
(v) Nitric acid (HNO₃)
Answer:
(i) 26g/mol
(ii) 256g/mol
(iii) 124 g/mol
(iv) 36.5g/mol
(v) 63g/mol.

Question 7.
What is the mass of the following?
(i) 0.2 moles atoms of oxygen.
(ii) 0.5 moles molecules of water
Answer:
(i) 3.2g.
(ii) 9g

Question 8.
Calculate the number of particles in each of the following:
(i) 46g Sodium atom (number from mass).
(ii) 8g Oxygen molecule (number of molecules from mass).
Answer:
(i) 12.044 x 10²³
(ii) 1.51 x 10²³

Question 9.
(i) Calculate the number of Sulphur (S₈) molecules In 16 g of solid sulphur.
(ii) Calculate the number of ions of Aluminium In 0.056 g of Aluminium Oxide (Al₂O₃).
Answer:
(i) 3.76 x 10²² molecules
(ii) 6.612 x 10²⁰ ions.

Question 10.
Calculate the percentage of each element en 1 mole ethyl alcohol (C₂H₅OH).
Answer:
C 52.17%, H 13.04%, 0 34.79%.

Question 11.
Calculate the percentage of oxygen In the following compounds:
(i) HgO
(ii) K₂CrO₇
(iii) Al₂
(iv) (SO)₃
Answer:
(i) 7.39%
(ii) 37.84%
(ii,) 56.14%.

Question 12.
What will be the mass in grams of the following compounds?
(i) 0.40 mole CO₂
(ii) 3.00 mole NH₃ mole
(iii) 5.14 mole H₅IO₆
Answer:
(i) 17.6 g
(ii) 512 g
(iii) 1171.92 g

Question 13.
A compound ‘X’ after analysing produces 85.72% carbon and 14.28% hydrogen. 1f the molar mass of the compound is 28, then find out its molecular formula.
Solution : Proportionality formula = C₂H₄

Essay Type Questions

Question 1.
Explain the method to find the molecular formula of a compound.
Answer:
By getting the following significant knowledge about an unknown compound, the molecular formula of the compound can be known:
(1) First of all, percent number of compounds should be known. For that, find out the percentage of different elements in the compound.
(2) Find out the atomic mass of elements in the Periodic Table.
(3) Find out the atomic ratio of elements by dividing per cent quantity of elements by atomic mass.
(4) To findthe simplest ratio of elements divide the ratio of elements by the least ratios among those.
(5) Write the symbols of elements side by side. On the right-hand side below them, write down the ratio of the concerned atom. Thus, the basic proportionality of the formula will be known.
(6) By writing the mass of elements in the basic proportionality formula, find out the mass of basic proportionality formula.
(7) Find out the proportionality number ‘n’ by dividing molecular mass with .baic proportionality mass for Thula.

(8) By multiplying basic proportionality formula with n molecular formula can be known Molecular formula basic proportionality formula xn.

Question 2.
Write down the formulae of the following compounds: .
(1) Hydrogen Chloride
(2) Hydrogen Sulphide
(3) Carbon tetrachloride
(4) Magnesium Chloride
(5) Calcium Oxide
(6) Aluminium Oxide.
Answer:
While writing the chemical formulae of molecular compounds, the symbols of each formed combined elements are written, thereafter, their valencies are written. Finally, the valencies of the combined atoms are crossed over and then the molecular formula is written.
(1) Formula of Hydrogen Chloride

∴ Formula of Hydrogen Chloride = HCl

(2) Formula of Hydrogen Sulphide

∴Formula of Hydrogen Suiphide H₂S

(3) Formula of Carbon tetrachioride

∴Formula oTCarbon tetrachlonde = CCl₄

(4) Formula of Magnesium Chloride

∴Formula of Magnesium Chloride = MgCl₂

(5) Formula of Calcium Oxide

Here the valences of both elements is same. Hence, its formula will be Ca₂O₂, but we write this formula in a simple form i.e., CaO.

(6) Formula of Aluminium Oxide

∴Formula of Aluminium Oxide = Al₂O₃

Question 3. Write down formulae of the compounds of the following: .
(i) Sodium nitrate
(ii) Calcium hydroxide
(iii) Ammonium sulphate
(iv) Sodium carbonate.
Answer:
(i) Formula of Sodium Nitrate

∴ Formula = NaNO₃
(ii) Formula of Calcium Hydroxide

∴ Formula Ca(OH)₂

(iii) Formula of Ammonium Sulphate

∴Formula = (NH₄)₂SO₄

(iv) Formula of Sodium Carbonate

∴Formula = Na₂CO₃

Practical Work

Experiment 1.
Prove with an experiment the law of solutions conservation of mass.

Procedure:
Prepare a 5% solution of copper sulphate and sodium carbonate in water. Now, take a little quantity of sodium carbonate solution in a conical flask and take a little quantity of copper sulphate in a test tube and suspend it into the conical flask in such a way that both the solvates should not get mixed up with each other as shown in the figure. After that fix it to the neck of flask and find its mass. Now, rotate the flask in a tilted position so that both the solutions get mixed up together. Now, again note down the mass of the flask. You will notice that before and after the activity the mass of the conical flask remains constant. This proves the law of mass conservation.

Experiment 2.
Describe an activity to explain the standard atomic mass unit.

Procedure:
Suppose a fruit seller is selling fruits without standard weights. He takes a watermelon and says “This has a mass equal to 12 units.” He chops the watermelon into 12 equal pieces and finds that the mass of each fruit being sold by him is relative to the mass of the single piece of the watermelon. As shown in the figure. Now, he sells the fruits by relative fruit mass unit (frnu). Thus, the relative atomic mass of an element is defined as average mass of its atoms w.r.f. the mass of 1/12 th part the mass of one carbon-l2 atoms.

Important Information And Tables

List of Symbols and Atomic Masses of Some Common Elements

Some Common, Simple and Polyatomic ions

Quick Review of the Chapter

1. Which Indian scientist gave name of atom to smallest indivisible particle of an element?
(A) Maharshi Kariade
(B) Pakudha
(C) Dr. Radha Krishan
(D) Dr. Raman
Answer:
(A) Maharshi Kanade

2. Who proposed the law of conservation of mass?
(A) Democratis
(B) Leucippus
(C) Lavoisier and Joseph L. Proest
(D) John Dalton
Answer:
(C) Lavoisier and Joseph L. Proest

3. Which Indian scientist gave name of atom to smallest indivisible particle of an element?
(A) Maharshi Kanade
(B) Pakudha
(C) Dr. Radha Krishan
(D) Dr. Raman
Answer:
(B) Pakudha

4. The atomic principle of John Dalton is:
(A) All liquids are composed of atoms
(B) Atoms are smallest indivisible particles
(C) The properties of atoms of an element
(D) All above mentioned
Answer:
(D) All above mentioned

5. The symbol of hydrogen proposed by Dalton was:

Answer:

6. According to Dalton, the symbol of phosphorus was:

Answer:

7. According to tUPAC, the symbol of cobalt is:
(A) K
(B) Co
(C) CO
(D) C
Answer:
(B) Co

8. According to IUPAC, the symbol of aluminium is:
(A) AL
(B) AL
(C) AL
(D) AI
Answer:
(D) Al

9. According to IUPAC, the symbol of silicon is:
(A) si
(B) SI
(C) Si
(D) Cl
Answer:
(C) Si

10. The atomic mass of hydrogen is:
(A) 1
(B) 2
(C) 4
(D) 6
Answer:
(A) 1

11. What ¡s the atomic mass of carbon?
(A) 4
(B) 6
(C) 12
(D) 16
Answer:
(C) 12

12. The number of atoms of oxygen present in Ozone is:
(A) 2
(B) 3
(C) 4
(D) 5
Answer:
(B) 3

13. What is the atom icity of sulphur?
(A) 8
(B) 7
(C) 5
(D) 3
Answer:
(A) 8

14. What is the atomic mass of sodium?
(A) 11
(B) 23
(C) 46
(D) none of these
Answer:
(B) 23

15. The atomic mass of chlorine is:
(A) 17
(B) 35
(C) 35.5
(D) 34
Answer:
(C) 35.5

16. What is the mass proportion of hydroge4n and oxygen in water?
(A) 1:4
(B) 1:8
(C) 8:1
(D) 1:16
Answer:
(B) 1:8

17. The mass proportion of nitrogen and hydrogen in ammonia is:
(A) 7:1
(B) 14:1
(C) 14:3
(D) 7:14
Answer:
(C) 14:3

18. The mass proportion of carbon and oxygen in carbon-dioxide is:
(A) 3:8
(B) 16:3
(C) 8:3
(D) 2:7
Answer:
(A) 3:8

19. The correct symbol of aluminium ion is:
(A) Al
(B) Al
(C) Al₂
(D) Al₃
Answer:
(D) Al3

20. What is the Latin name of iron element?
(A) Ferum
(B) Cuprum
(C) Kalium
(D) Natrium
Answer:
(A) Ferum

21. What is the chemical formula of hydrogen chloride?
(A) HCl
(B) HCl₂
(C) HCl₃
(D) H₂Cl
Answer:
(A) HCl

22. The chemical formula of hydrogen suiphide is:
(A) HS
(B) H₂S
(C) H₂S₂
(D) H₂S₃
Answer:
(B) H₂S

23. What ¡s the formula of carbon tetrachioride?
(A) C₄Cl
(B) CCl
(C) CCl₄
(D) C₄Cl₄
Answer:
(C) CCl₄

24. What is the formula of sodium carbonate is:
(A) NaCO₃
(B) NaCO₂
(C) Na₂CO₃
(D) Na₃CO₃
Answer:
(C) Na₂CO₃

25. The chemical formula of common salt is:
(A) NaCl
(B) MgCl
(C) CaCl₂
(D) Ca(OH)₂
Answer:
(A) NaCI

26. The molecular mass HNO₃ is:
(A) 53u
(B) 63u
(C) 73u
(D) 58.5 u
Answer:
(B) 63 u

27. What is the molecular mass of NaCl?
(A) 36.5 u
(B) 35.5 u
(C) 58.5 u
(D) 63 u
Answer:
(C) 58.5 u

28. What is the molecular mass of CaCl₂?
(A) 98.2u
(B) 111u
(C) 112u
(D) 114.2 u
Answer:
(B) IIlu