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Haryana State Board HBSE 8th Class Science Solutions Chapter 3 Synthetic Fibres and Plastics Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 3 Synthetic Fibres and Plastics

HBSE 8th Class Science Synthetic Fibres and Plastics Textbook Questions and Answers

Question 1.
Explain why some fibres are called synthetic?
Answer:
Some fibres are called synthetic because they do not occur naturally and are made by man using petrochemicals.

Question 2.
Mark (✓) the correct answer:

Rayon is different from synthetic fibre because
(i) it has a silk like appearance
(ii) it is obtained from wood pulp
(iii) its fibres can also be woven like those of natural fibres.
Answer:
(ii) it is obtained from wood pulp. ✓

Question 3.
Fill in the blank with appropriate words:
(i) Synthetic fibres are also called ……………. or ……………. fibres.
(ii) Synthetic fibres are synthesised from raw material called ……………. .
(iii) Like synthetic fibres, plastic is also a ……………. .
Answer:
(i) man-made or artificial fibres
(ii) petrochemicals
(iii) polymer.

Question 4.
Give examples which indicate that nylon fibres are very strong.
Answer:
Nylon fibres are very strong, thus they are used to prepare ropes for mountaineering. They are also used to prepare parachutes.

Question 5.
Explain why plastic containers are favoured for storing food.
Answer:
Advantanges of storing foods in plastic containers are:
(a) the plastics do not react with the food stored in them.
(b) the plastics are light weight and are strong.
(c) they are easy to handle and safe.

Question 6.
Explain the difference between the thermoplastic and thermosetting plastics.
Answer:
Differences between thermoplastic and thermosetting plastics:
(i) Thermoplastics can be mtelted on heating but thermosetting plastics Cannot be melted.
(ii) Thermoplastics can be reshaped as many times as desired but thermosetting plastics cannot.
(iii) Thermoplastics can be bent but thermosetting plastics cannot be bent.
(iv) Thermoplastics are good conductors of heat, thermosetting plastics are bad conductors of heat.

Question 7.
Explain why the following are made of thermosetting plastics:
(a) Saucepan handles
(b) Electric plugs/switches/plug boards.
Answer:
(a) The handles of saucepan are made of thermosetting plastic because it is a bad conductor of heat and do not get heated up while cooking. So it becomes easy to handle the utensil while cooking.
(b) Electric plugs/ switches and plug boards are made up of thermosetting plastic because it is a bad conductor of electricity. It does not allow the electric current to pass through it, thus safe in using in electric appliances.

Question 8.
Categorise the materials of the following products into ‘can be recycled’ and ‘cannot be recycled’.
Telephone instruments, toys, cooker handles, carry bags, ball point pens, plastic bowls, electric wire covering, plastic chairs, electrical switches.
Answer:
Can be Recycled: Toys, carry bags, plastic bowls, ball point pen, plastic chairs, electric wire covering.
Cannot be Recycled: Cooker handles, electric switches, telephone instruments.

Question 9.
Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from synthetic material? Advise Rana, giving your reason.
Answer:
Cotton clothes are preferred to synthetic clothes in summers because cotton is a bad conductor of heat. It does not allow the outer heat to enter in our body, thus protects body from heat. It also has more capacity to hold moisture than the synthetic clothes. So, it retains
the sweat of the body and keeps it cool. So, Rana should buy shirts made upof cotton.

Question 10.
Give examples to show that plastics are noncorrosive in nature?
Answer:
Following examples show that plastics are non-corrosive in nature:
(i) They are used to store chemicals in laboratories.
(ii) They are used to store all types of food, as it does not react to materials stored in it.
(iii) It does not even react with air and water.

Question 11.
Should theiiandle and bristles of a tooth brush be made of the same material? Explain your answer.
Answer:
No, the handle and bristles of a tooth brush should not be made of the same material because the bristles should be soft and the handle should be hard. So the bristles should be made up of soft material so that it does not harm the gums. The handles should be made up of hard material so that it can give firm grip.

Question 12.
‘Avoid plastics as far as possible,’ Comments on this advice.
Answer:
Plastics are harmful for our environment. Some of the plastics cannot be recycled, so they cannot be used again and thus cannot be finally disposed off. They thus, should be avoided as far as possible.

Question 13.
Match the terms of column I correctly with the phrases given in column II:

Answer:

Question 14.
‘Manufacturing synthetic fibres is actually helping conservation of forests’. Comment.
Answer:
Manufacturing synthetic fibres is actually helping conservation of forests because it does not require cfutting plants and hunting animals to get the natural fibres. The synthetic fibres are made up of chemicals and these chemicals are not available in forests.

Question 15.
Describe an activity to show that thermoplastic is a poor conductor of electricity.
Answer:
Observe all the electric wires of your house from a distance. You can take an electric wire which is not carrying current. Open the main wire you will see three/two small wires in the main wire and will see that they have covering of red, green and yellow plastic covering. This proves that the thermoplastics are bad conductors of electricity.

Extended Learning – Activities And Projects

1. Have you heard of the campaign: “Say No To Plastics”. Coin a few ihore slogans of this kind. There are certain governmental and non-governmental organisations who educate general public on how to make a wise use of plastics and develop environment friendly habits. Find, out organisations in your area which are . carrying out awareness programmes. If there is none, form one. .
Answer:
For self attempt. .

2. Organise a debate in the school. The children may be given an option to rule play as manufacturers of synthetic fabrics or those of fabrics from natural sources. They ican then debate on the topic “My Fabric is Superior.”
Answer:
For self attempt.

3. Visit five families in your Neighbourhood and enquire about the kind of clothes they use, the reason for their choice and advantages of using them in term: of cost, durability and maintenance. Make a short report and submit it to your teacher.
Answer:
For self attempt.

4. Devise an activity to show that organic waste is biodegradable while plastic is not.
Answer:
Take some organe peels or peels of any fruit or vegetable. Now take any broken object of plastic.
Take two flower pots. In one pot dig a small pit and throw peels and cover it with mud. In second pot put the plastic and cover it with mud. Observe them after 5-10 day, and you will see that the peels have started decomposing and nothing has happened to plastic toy.

5. If you wish to know more about fibres and plastics and the products made from them, you may explore the following web sites:
• http://www.pslc.ws/macrog/index.htm
• http://www.edugreenteri.res.in/ exploresolwaste/types/htm
• http://www.nationalgeographic.com/ resouces/ngo/eduction/plastics
• http://www.packagingtoday.com/
• http://www.bbc.co.uk/schools.gcsebitesize/ design/textiles/fibresrev/html/

HBSE 8th Class Science Synthetic Fibres and Plastics Important Questions and Answers

Very Short Answer Type Questions

Question 1.
Why do we wear clothes?
Answer:
We wear clothes to get protected from heat, cold and other outer conditions.

Question 2.
How many types of fibres are there?
Answer:
There are two types of fibres: Natural fibre and Synthetic fibres.

Question 3.
What are natural fibres?
Answer:
Fibres obtained from animals and plants are called natural fibres.

Question 4.
What are synthetic fibres?
Answer:
Fibres made of chemicals by the man are called synthetic fibres.

Question 5.
Name some natural fibres.
Answer:
Silk, wpol, cotton, jute, etc.

Question 6.
Name some synthetic fibres.
Answer:
Nylon, rayon, polyester, Acrylic.

Question 7.
What are polymers?
Answer:
Polymers are small jinits which combindfo make a synthetic fibre.

Question 8.
Name one natural polymer.
Answer:
Cellulose is a polyiper of cotton.

Question 9.
Which synthetic fibre is called synthetic silk?
Answer:
Rayon.

Question 10.
Which country discovered silk for the first time?
Answer:
China.

Question 11.
Which raw material is used to make rayon?
Answer:
Wood pulp.

Question 12.
Which raw material is used to make Nylon?
Answer:
Coal, water and air.

Question 13.
Name few items made from nylon.
Answer:
Socks, ropes, tents, sleeping bags, parachutes, etc.

Question 14.
Which is the strongest synthetic fibre?
Answer:
Nylon.

Question 15.
Which synthetic fibre can be stronger than a steel wire?
Answer:
Wire made of nylon.

Question 16.
Name a synthetic fibre which works like wool.
Answer:
Acrylic.

Question 17.
What happens when synthetic fibre is burnt?
Answer:
It starts melting.

Question 18.
What are petrochemicals?
Answer:
Petrochemicals are raw materials processed to make synthetic fibres.

Question 19.
Name a few properties of plastics.
Answer:
They can be moulded, recycled, reused and melted.

Question 20.
What use polythene is put to?
Answer:
Polythene is used to make carry bags.

Question 21.
What do we call the plastics which can be remoulded again and again?
Answer:
Thermoplastics.

Question 22.
What do we call the plastics, which cannot be remoulded and reused?
Answer:
Thermosetting plastics.

Question 23.
Why electric switches and plugs are made of plastics?
Answer:
They are resistant to electricity.

Question 24.
Which material is used to make non-stick utensils?
Answer:
Teflon.

Question 25.
Which material is used to make the handles of the cookware?
Answer:
Melamine.

Question 26.
What makes plastic a wonder material?
Answer:
Lightness, strength, durability and non-reactiveness.

Short Answer Type Questions

Question 1.
Distinguish between Natural fibre and Synthetic fibre.
Answer:
Natural fibres are obtained from natural resources like plants and animals e.g., cotton, jute, etc. are obtained from plants. Silk and wool are obtained from animals. Synthetic fibres are made from synthetic materials, like petrochemicals, e.g. Nylon, Terelene, acrylic etc.

Question 2.
Why silk is so costly?
Answer:
Silk is a natural fibre obtained from silk moth. It takes a lot of time and efforts to make silk. So, it costs high.

Question 3.
What is Polyester?
Answer:
Polyester is the word coined by joining ‘poly’ and ‘ester’. This synthetic fibre is made by joining many ester units. Ester is a chemical which causes smell in fruits.

Question 4.
What makes acrylic more popular than pure wool?
Answer:
Acrylic is a synthetic fibre. It resembles wool in looks and in qualities. Wool is expensive becuse it is obtained from natural sources but acrylic is cheaper and is available in vibrant colours. It is more durable than wool.

Question 5.
What is the main disadvantage of synthetic fibre?
Answer:
Synthetic fibres are good conductors of heat. They melt when heated. This causes a great danger for the user. In case the fibre catches fire while working in the kitchen, it will stick to the user’s body and will cause great damage to skin.

Question 6.
Which fibre will you prefer to get your raincoat stitched? Why?
Answer:
We will prefer synthetic fibre for getting our raincoat stitched because it will not absorb much amount of water and dispell it saving us from rain water. It will also dryup soon later.

Question 7.
How can polythene carry bags be harmful for animals?
Answer:
Polythene carry bags are thrown here and there after using them. Stray cattle consume them. In this case, it can choke the respiratory system and damage their stomach. It can even cause their death.

Question 8.
What are thermoplastics? Explain with examples.
Answer:
Those plastics which can melt on heating and which can be reshaped on moulding again and again are called thermoplastics P.V.C., Polythene are examples of thermoplastics. Toys, containers, car grills, combs etc. are made with thermoplastics.

Question 9.
What are thermosetting plastics?
Answer:
Thermosetting plastics are those plastics, which can be only moulded for once. They cannot be reshaped or reused because they do not get softened op heating. Bakelite, melamine etc. are examples of thermosetting plastics.

Question 10.
What are biodegradable and non-biodegradable materials?
Answer:
Biodegradable substances are those substances which can be decomposed by bacteria and other natural processes. Those substances which cannot be decomposed are called non-biodegradable substances. Plastics are non-biodegradable.

Long Answer Type Questions

Question 1.
Distinguish between natural fibres and synthetic fibres.
Answer:

Question 2.
Name different artificial fibres and write their uses.
Answer:
Following are the main synthetic fibres:
(i) Rayon:
It is also called the artificial silk as it has great lustre and is fight in weight. It is obtained by the chemical treatment of wood pulp. It can be woven like silk and dyed in different colours. It is used as dress material. Mixed with cotton, it is used to make curtains, bedsheets etc. It is mixed with wool to make beautiful carpets.

(ii) Nylon:
It is the strongest fibre. It is made by coal, water and air. It is elastic in nature and fight in weight. It is lustrous and thus ideal for making dresses. It is also used to make stockings, seat belts, ropes, tents, toothbrushes, sleeping bags, curtains and parachutes, etc.

(iii) Polyester:
It is made up of multiple units of ‘esters’. The clothings made of this fibre do not get wrinkled easily. It is always crisp and easily washable. PET is also derived from polyester which ip turn is used to make containers, utensils, films, wires etc.

(iv) Acrylic: Acrylic is just like wool and is used to make sweaters and suit lengths.

Question 3.
Describe the characteristic features of the synthetic fibres.
Answer:
Synthetic fibres are made from chemical substances. Their qualities are quite different from those of natural fibres. Following are the characteristic features of the synthetic fibres:
1. Raw material: All synthetic fibres are made from chemicals. They are prepared by a number of processes using raw materials of petroleum family called petrochemicals.

2. Strength: Synthetic fibres are quite strong. Nylon is the strongest known fibre.

3. Durability: Synthetic fibres are quite durable. They do not wither easily. They are so strong and durable that ropes and parachutes etc. are made by using synthetic fibres.

4. Soak less water: Synthetic fibres absorb small quantities of water and loose it quick, so they dry up very soon.

5. Availability and cost: Synthetic fibres are less expensive and readily available. That makes it a popular dress material.

Question 4.
What are plastics? How many types of plastics are available? Explain.
Answer:
Plastics are synthetic materials which can be moulded to give any desirable shape. Plastics are two types:
Thermoplastics: Those plasties which can be melted and reshaped again and again to give any shape on heating are called thermoplastics. Thermoplastics can be reused as many times as desirable e.g. PVC and polythene.

Thermosetting Plastics are those plastics which can be melted on heating mid cannot be reshaped again and again. Melamine, Bakelite etc. are examples of thermosetting plastics.

Question 5.
Write the characteristic features of plastics.
Answer:
Plastic is a wonder material. Following characteristic features make it a common and popular choice:
(i) Plastics are light in weight so they are easy to handle and manage.
(ii) Plastics are strong and durable so they are used to make buckets, mugs, ropes, etc.
(iii) Plastics are non-reactive as they do not get corroded when they come in contact with other materials or substances. This property make them perfect for storing food items and chemicals.
(iv) Plastics are poor conductors of electricity. They do not allow the electric current to pass through them easily. They are, therefore, used to make coverings of electric wires and other electric appliances.

Question 6.
Write advantages and disadvantages of synthetic fabrics.
Answer:
Following are the advantages of synthetic fabrics:
(a) Most of the synthetic fibres are wrinkle resistant. They do not get wrinkled easily. They easily retain their original shape, if they get wrinkled. So it is convenient to wash and wear.
(b) Synthetic fibres are strong so they can take up heavy loads easily. They have got high tensile strength, which enables them to carry weights.
(e) They have great elasticity. They can be easily streched.
(d) Synthetic fibres are generally soft, so they are used to make variety of clothes and clothing materials.

Disadvantages:
(a) Synthetic fibres cannot absorb moisture. This makes them unsuitable to be warm during summers. When our body sweatsv This make body sticky and irritates the skin
(b) They are dangerous to be worn near fire or heat, as they easily catch fire and is unfit to he worn.
(c) They cannot be easily ironed as they melt very easily.

Question 7.
How disposal of plastic is a problem? Explain.
Answer:
Plastic is wonderful synthetic material which is very useful. But biggest disadvantage of plastic is its disposal. Plastic is a non- biodegradable subtance, which do not get decomposed on its own by other microorganisms. So, accumulation of plastic is causing great danger for environment in the following ways:
(i) We throw plastics openly on roadsides and streets. This provide home to many disease causing germs.
(ii) Plastics if burned in the soil create more problem. They cannot be decomposed and prevents the water from seeping into the soil. This affects the plants adversLy. Water gets accumulated on the soil and cause muddy pubbles.
(iii) Buring the plasties produce toxic gases alongwith smoke which cause air pollution. Such an air is unfit for consumption and give birth to many respiratory problems in animals.
(iv) Plastic waste when dumped in water, cause water pollution. Aquatic animals consume these toxic plastics and die. It can also cause reproductive problems in aquotic animals.

Synthetic Fibres and Plastics Class 8 HBSE Notes

1. All the clothes we wear are made up of fabrics. Fabrics in turn are made up of fibres. Fibres can be of two types: natural fibre and manmade or synthetic fibres.
2. Natural fibres are those fibres which we get from plants and animals e.g. cotton, wool, silk, jute, etc.
3. Artificial or synthetic fibres are made up of the chemical substances by processing in factories and mills.
4. A synthetic fibre is chain of small units, woven together to form a long chain. These chemical substances or this chain of small units is called a polymer. All synthetic fhbrics are made up of these repeating units called polymers.
5. Rayon, Nylon, polyester etc. are examples of the manmade fibres.
6. These synthetic fibres are used for many other purposes, except making clothes. Nylon is a very strong fibre. It is used to make parachutes, socks, ropes, toothbrushes, sleeping bags and other drappery accessories.
7. Synthetic fibres are stronger than natural fibres. They absorb lesser amount of water than, the natural fibres. That is why raincoats etc. are made up of the synthetic fibres. They get dry! very soon and need less care and maintenance.
8. Plastics are synthetic materials which are used for many purposes. We can see objects made up of plastics all around us.
9. Plastics are also made up of polymers. Plastics can be moulded, melted and recycled. But all plastics are hot same.
10. Plastics are of two types: Plastics which can be melted, reshaped, bent easily are known as thermoplastics. The plastics which cannot be melted or reshaped are called thermosetting plastics.
11. Thermoplastics are used to make toys, combs, containers, etc. P.V.C. is an example of thermoplastic.
12. Thermosetting plastics are poor conductors of heat and are resistant to electricity. So they are used to make handles of utensils, electric plugs and switches, etc.
13. Plastics are very useful for us in every sphere of life. But they do have their disadvantages too.
Plastics are non-biodegrada,ble, so we cannot get rid of waste plastic easily. It is causing threat to our environment.
14. Environment friendly habbits like Reduce, Reuse, Recycle and Recovery of plastics can help in saving Environment.

Haryana State Board HBSE 8th Class Science Solutions Chapter 2 Micro Orgmisms: Friends and Foe Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 2 Micro Orgmisms: Friends and Foe

HBSE 8th Class Science Micro Orgmisms: Friends and Foe Textbook Questions and Answers

Question 1.
Fill in the blanks:
(a) Microorganisms can be seen with the help of a ……….. .
(b) Blue green algae fix ………….. directly from air to enhance fertility of soil.
(c) Alcohol is produced with the help of ………….. .
(d) Cholera is caused by ……………… .
Answer:
(a) microscope
(b) atmospheric nitrogen
(c) yeast
(d) bacteria.

Question 2.
Tick the correct answer:
(a) Yeast is used in the production of:
(i) sugar
(ii) alcohol
(iii) hydrochloric acid
(iv) oxygen
Answer:
(ii) alcohol

(b) The following is an antibiotic:
(i) Sodium bicarbonate
(ii) Streptomycin
(iii) Alcohol
(iv) Yeast
Answer:
(ii) Streptomycin

(c) Carrier of malaria-causiiig protozoan is:
(i) female Anopheles mosquito
(ii) cockroach
(iii) housefly
(iv) butterfly
Answer:
(i) female Anopheles mosquito

(d) The most common carrier of communicable diseases is:
(i) ant
(ii) housefly
(iii) dragonfly
(iv) spider
Answer:
(ii) housefly

(e) The bread or idli dough rises because of:
(i) heat
(ii) grinding
(iii) growth of yeast cells
(iv) kneading
Answer:
(iii) growth of yeast cells

(f) The process of conversion of sugar into alcohol is called:
(i) nitrogen fixation
(ii) moulding
(iii) fermentation
(iv) infection
Answer:
(iii) fermentation

Question 3.
Match the organisms in Column I with their action in Column II.

Answer:

Question 4.
Can microorganisms be seen with the naked eye? If not, how can they be seen?
Answer:
Some organisms are very small in size. They are so small that they cannot be seen with naked eyes. A microscope has to be used to see these organisms. Therefore, they are called microorganisms.

Question 5.
What are the major groups of microorganisms?
Answer:
Microorganisms can mainly be divided into five groups:
(i) Bacteria
(ii) fungi
(iii) protozoa
(iv) algae,
(v) virus.

Question 6.
Name the microorganisms which can fix atmospheric nitrogen in the soil.
Answer:
Bacteria like Rhizobium, Azotobacter, Blue green algae like Anabaena and Nostoc can fix atmospheric nitrogen in soil.

Question 7.
Write 10 lines on the usefulness of microorganisms in our lives.
Answer:
Microorganisms are very useful to us.
They help us in following ways:
(i) Microorganisms help us in food sector. They are used for curdling of milk, preparation of bread, cake, etc.
(ii) Microorganisms are used to produce alcohol at large scale.
(iii) They are also used to produce wine.
(iv) Yeast is used to prepare vinegar.
(v) They are also used as preservatives for food items.
(vi) Used to make different medicines, especially the antibiotics.
(vii) Microorganisms are used to prepare vaccines for various disease.
(viii) Useful for agriculture sector, as they enhance the fertility of soil by fixing the biological nitrogen.
(ix) They work as natural cleansers, as they decompose the dead bodies of plants and animals.
(x) Microorganisms prepare manures by decomposing dead bodies of plants and animals.

Question 8.
Write a short paragraph on the harms caused by microorganisms.
Answer:
Microorganisms can prove very harmful to us, as they cause a number of human and animal diseases. Diseases in humans like common cold, tuberculosis, measles, chiken pox, Polio, Cholera, Typhoid, Hepatitis B, Malaria, etc. are caused by microorganisms. Some serious deseases like Anthrax is also caused in animals by the microbes. Microbes grow on food products and render them unfit for consumption.

Consumption of such food causes food poisoning. Microbes also spoil clothings and leather products. Microbes also cause diseases of plants like blights in potatoes, sugarcanes, oranges etc. They also reduce the yield.

Question 9.
What are antibiotics? What precautions must be taken while taking antibiotics?
Answer:
Medicines taken to kill or stop the growth of harmful or disease causing microbes in human body are called antibiotics. Antibiotics are very useful as only antibiotics can save us from many microbial infections and diseases. Antibiotics are made from fungi and bacteria. Alexander Fleming discovered the first antibiotic called Penicillin in 1929. Now-a-days a number of antibiotics are used to cure a variety of human and animal diseases. Streptomycin, Tetracycline, Erythromycin etc. are some commonly used antibiotics.

Antibiotics should only be taken when adviced by a qualified physician. Antibiotics should only be taken when needed otherwise, they become less effective for future use.

Extended Learning – Activities And Projects

1. Pull out a gram or bean plant from the field. Observe its roots. You will find round structures called root nodules on the roots. Draw a diagram of the root and show the root nodules.
Answer:
Do it yourself.

2. Collect the labels from the bottles of jams and jellies. Write down the list of contents printed on the labels.
Answer:
Ingredients: Sugar, Mixed fruit pulp, Gelling Agent (E440), And acidity regulator (E330). Permitted synthetic food colour (E122) and added artificial flavours. Contains permitted class-II Preservatives (E211, E224).

3. Visit a doctor. Find out why antibiotics should not be overused. Preapare a short report.
Answer:
Antibiotics should not be overused because they reduce of power of immunity.
(i) Regular or frequent use make the drug ineffective when needed in future.
(ii) They kill beneficial bacteria in our body.
So, antibiotics should only be consumed when prescribed by doctore only.

4. Project:
Requirement – 2 text tubes, marker pen, sugar, yeast powder, 2 ballons and lime water.

Take two test tubes and mark them A and B. Champ these tubes in a stand and fill them with water leaving some space at the top. Put two spoonfuls of sugar in each of the test tubes. Add a spoonful of yeast to test tube B. Inflate the two balloons incompletely Now tie the balloons on the mouths of each test tube. Keep them in a warm place, away from sunlight. Watch the setup every day for next 3-4 days. Record you observations and think of an explanation.

Now take another test tube filled V4 with lime water. Remove the balloon from test tube B in such a manner that gas inside the balloon does not escape. Fill the balloon on the test tube and shake well. Observe and explain.
Answer:
The balloon in test tube B will get inflated because process of fermentation has taken place in test tube B due to yeast bacteria and carbondioxide gas produce during this process has inflated the balloon. Now the balloon will get a little deflated as gas in consumed by the lime water and the lime water will turn milky.

5. For more information, visit the following websites.

• www.microorgan.isms
• www.biology4kids.com/files/micro_main html

HBSE 8th Class Science Microorganisms: Friend and Foe Important Questions and Answers

Very Short Answer Type Questions

Question 1.
Define microorganisms.
Answer:
Very small organisms around us which cannot be seen with naked eyes are called microorganisms.

Question 2.
Where are microorganisms found?
Answer:
Microorganisms are found everywhere. In air, water and in the body of other organisms.

Question 3.
Name the groups in which microorganisms can be divided.
Answer:
Bacteria, fungi, protozoa, some algae and viruses.

Question 4.
Which common diseases do viruses cause?
Answer:
Viruses cause diseases like common cold, flu and most of the coughs.

Question 5.
Which serious diseases are caused by viruses?
Answer:
Diseases like polio and chicken pox.

Question 6.
Name diseases caused by protozoans.
Answer:
Dysentery and malaria are caused by protozoans.

Question 7.
Name any two algae.
Answer:
Chlamydomonas and spirogyra.

Question 8.
Name any two protozoa.
Answer:
Amoeba and paramecium.

Question 9.
Name any two fungi.
Answer:
Rhizopus and Aspergillus.

Question 10.
Name unicellular microbes.
Answer:
Bacteria and protozoa.

Question 11.
Name multicellular microbes.
Answer:
Algae and fungi.

Question 12.
Which bacteria is responsible for the curdling of milk?
Answer:
Lactobacillus.

Question 13.
Which bacteria is used to produce alcohol?
Answer:
Yeast.

Question 14.
What do you mean by fermentation?
Answer:
Conversion of sugar into alcohol using yeast is palled fermentation.

Question 15.
Who discovered the process of fermentation?
Answer:
Louis Pasteur.

Question 16.
What are antibiotics?
Answer:
Medicines used to kill or stop the growth of diseases causing microorganisms inside human body are called antibiotics.

Question 17.
Who discovered the first antibiotic?
Answer:
Alexander Fleming.

Question 18.
Which antibiotic did Alexander Fleming discover?
Answer:
Penicillin.

Question 19.
Which microorganism is not affected by antibiotics?
Answer:
Viruses.

Question 20.
Name certain diseases which can be prevented by vaccination.
Answer:
Cholera, tuberculosis, small pox, hepatitis, polio, etc.

Question 21.
Name microorganisms which can fix atmospheric nitrogen.
Answer:
Bacteria and blue green algae.

Question 22.
Name one free living bacteria and one blue green algae who fix nitrogen using oxygen from atmosphere.
Answer:
Azotobacter, Anabaena.

Question 23.
What are pathogens?
Answer:
Disease causing microorganisms are called pathogens.

Question 24.
What are communicable diseases?
Answer:
Diseases which spread with physical contacts are called communicable diseases.

Question 25.
Name an insect which is a common carrier of microbial diseases.
Answer:
Housefly.

Question 26.
Name the carrier of dengue virus.
Answer:
Female Aedes mosquito.

Question 27.
Where do mosquitoes breed?
Answer:
Mosquitoes breed in stagnant water and damp places.

Short Answer Type Questions

Question 1.
What are the major group of the microorganisms?
Answer:
Major groups of microorganisms are:
(i) Bacteria: They are non-green single celled microorganisms.
(ii) Fungi: They are long thread like unicellular as well as multicellular microorganisms.
(iii) Algae: Aquatic* photosynthetic organisms commonly called sea weeds.
(iv) Protozoan: They are unicellular organisms.
(v) Virus: They are non-cellular microbes which only get active inside a living cell.

Question 2.
Describe various types of bacteria with examples.
Answer:
On the basis of their shape, the bacteria are divided into three types:
(i) Bacillus or rod shaped: Long rod shaped bacteria like Bacillus, Pseudomonas, Lactobacillus.
(ii) Cocus or round shaped: Streptococus, Sarcinaltc. are round shaped bacteria.
(iii) Spirillum or spiral: Comma shaped bacteria, they can also be spiral rods e.g. Camphilovector, Triponema.

Question 3.
State some beneficial effects of bacteria.
Answer:
Bacteria are very useful to us. Some of the beneficial effects of bacteria are as follows:
(i) Bacteria is helpful in agriculture as it fixes the atmospheric nitrogen in soil.
(ii) Products like vinegar, alcohol, curd etc. are obtained.
(iii) It decomposes the dead bodies of plants and animals.
(iv) Valuable medicines like antibiotics are obtained by bacteria.

Question 4.
Mention important uses of fungi,
Answer:
(i) Some fungi are eaten raw as food such as mushrooms.
(ii) Yeast being rich in amino acids and proteins are an important source of food for man and his farm animals.
(iii) Yeast is also used in the preparation of products like wine and bears from fruit juices or barley. It brings about fermentation of sugars into alcohols and carbondioxide.

Question 5.
Write the harmful effects of Bacteria.
Answer:
Bacteria cause a number of diseases in humans and animals. Diseases like cholera, pneumonia, tuberculosis are caused by bacteria. It also causes food poisoning as it makes the food unfit to consume. It spoils leather and clothings.

Question 6.
Write the harmful effects of fungi and algae.
Answer:
Some fungi causes damages or diseases. Smuts and rusts are fungi that damage the crops. Ring-warm and atheletes food diseases are caused by fungi. Amanite mushrooms contain poisonous substance. Algae are great nuisance as they spoil the drinking water. Excess growth of algae also blocks the movement of water in channels.

Question 7.
Write the diseases caused by protozoa.
Answer:
Several protozoa cause diseases in man and other animals. Antaemoeba Histolytica causes amoebic dysentry in man. Dangerous plasmodium causes malaria and dengue. Trypanosoma, causes sleeping sickness in man, cattle, pigs and horses.

Question 8.
Describe the main characteristics of viruses in brief.
Answer:
(i) They do not possess any cell wall or cell membrane.
(ii) They can only multiply in the bodies of living beings.
(iii) They cause many diseases.
(iv) Antibiotics do not have any affect on viruses.

Question 9.
What are vaccines?
Answer:
A vaccine consists of antigens of mild strains of pathogens of a particular disease. Vaccine when injected into the blood stream stimulates white blood cells to produce antibodies. These antibodies act against the antigens and neutralise their toxins or destroy them.

Question 10.
How does microorganisms enter into our body?
Answer:
Microorganisms enter into our body:
(i) through the air we breathe.
(ii) through the water we drink.
(iii) through direct contact with infected person.
(iv) by the use of polluted water or food.

Question 11.
What are viruses?
Answer:
Viruses are microscopic organisms. These are the smallest organisms. They may be rod-shaped, polygonal, spherical or even cubical. There are four types of viruses: Plant viruses, Insect viruses, Bacterial viruses and mammalian viruses.

Long Answer Type Questions

Question 1.
What do you understand by microorganisms? Describe their different forms.
Answer:
Different living organisms present around us which cannot be seen with naked eyes are called microorganisms. They are present in soil, water and air. Microorganisms can be divided into five groups:
(i) Bacteria are the non-green single celled microscopic organisms. They have a rigid cell wall. It has a nuclear material. They are the simple most common form of life on earth. They have different shapes and sizes.

(ii) Algae are aquatic, photosynthetic organisms. In simple terms they are called sea weeds. They range in size, colour. Algae are of green, blue, red and blue^green colours.

(iii) Fungi are plants not having chloroplast but a cell wall. They are both unicellular and multicellular. Moulds, mushrooms etc. are fungi.

(iv) Protozoa are one celled living things. They range from 2 to 200 microns. Amoeba, Paramecium, Euglena and Plasmodium etc. are protozoas.

(v) Viruses are the non-cellular microbes. They are smaller than bacteria and multiply only inside a living cell.

Question 2.
Write a short note on Bacteria.
Answer:Bacteria are non-green single celled microscopic organisms. They have a rigid cell wall. They have a nuclear material. They are simple most common form of life on earth. They occur singly but are seen in chain of cells. They are of different shapes such as rod shaped, spiral, cork screw and comma shaped.

Bacteria are harmful for us, but some bacteria are quite useful. The most disadvantageous aspect of bacteria is their disease causing tendency. Various serious diseases like Tuberculosis, cholera, typhoid etc. are caused by bacteria. Bacteria are useftd as they are used to prepare vaccines and antibiotics. They decompose waste material and fix the atmospheric nitrogen into soil to enhance its fertility. Bacteria are also used to manufacture vinegar, acetic-acid, curd and cheese etc.

Question 3.
What are fungi? How are they useful or harmful to us?
Answer:
Fungi are microorganisms which exist in unicellular as well as multicellular forms. Some of the fungus like mushroom, yeast etc. can be seen with naked eyes. They have long thread like structures called hyphae. Fungus can reproduce sexually as well as asexually. Fungi are both harmful and useful. Smuts, crusts and ringworm etc. cause many diseases in humans as well as in animals and plants.

They are useful as they are used as food in many parts of world. Mushrooms are the mostly used food around the word. Yeast is used to make alcohol, breads, bhathuras, idlis, dosas etc. Penicillium is used to make penicillin an antibiotics.

Question 4.
What do you know about Protozoa?
Answer:
Protozoa are single celled living things. The size ranges from 2 microns to 200 microns.

Amoeba, Paramesium, Euglena, Plasmodium etc. are examples of Protozoa. Protozoa are the part of animal kingdom because they do not have chlorophyll.

They are oval, elongated and spherical in shape. Protozoa cause diseases like malaria and dengue. Protozoa like Entamoeba Histolytica causes amoebic dysentery in man. Trypanosoma causes sleeping sickness in man and cattle. Protozoa are useful as they form an important link in acquatic food chain. They decompose organic matters to convert them in useful soil nutrients.

Question 5.
What are food preservatives? Explain some common preservatives.
Answer:
Chemicals used to check or stop the growth of harmful microorganisms in food are called preservatives. These preservatives keep the edibles protected from the invasion of microorganisms which can spoil the food.
Some commonly found preservatives are:
Salt: Common salt is used to preserve meat, fish, amla, raw mangoes, tamarind, etc.

Sugar preserves jam, jellies, squashes and other sweet drinks. Sugar reduces the moisture and checks the growth of microorganisms.

Oil: Edible oils are used as preservatives in vegetables and pickles. Oil does not allow the moisture to surface thus preventing the growth of harmful bacteria.

Vinegar preserves vegetables, fruits, fish, meat and pickles.
Other processes like pasteurization etc. also preserve the milk and other liquids.

Question 6.
How can we detect the spoilage in food?
Answer:
Following indications help us an detecting the spoilage in food:
(a) Odour:
When food gives out smell, it is the indication that the bacteria has spoiled the food. Food gives out repulsive smell when bacteria breaks the proteins found in food. This is called Putrefaction.

(b) Discoluration:
Growth of microbes on food results in discolouration of food black. Moulds on breads, blue green moulds on citrus fruits and cheese cause the change in the original colour of the food. Any small discolouration indicates that the food has been spoiled and is unfit for consumption.

(c) Souring:
Sometimes the cooked food starts tasting sour. It is due to the production of acids by the action of certain bacteria. Milk starts tasting sour if not preserved properly, same is the case with curries and gravies of some vegetables.

(d) Sliminess:
Sometimes the food became slimy. It is also due to action of certain bacteria thread like slimes are also caused due to moulds.

(e) Gas formation:
Due to action of bacteria gases like carbondioxide are produced. They also spoil the food by making it swell or become spongy.

Microorganisms: Friend and Foe Class 8 HBSE Notes

1. Many living organisms exist around us in water, soil and air. They are so small that they cannot be seen with naked eyes. These tiny organisms are called microorganisms or microbes.
2. Microorganism can live in any kind of extreme environment like hot, cold, humid, icecold, saline water, desert or hot soil.
3. Microorganisms have wide variety of structural forms. They can be from unicellular to multicellular organisms.
4. Microorganisms are classified as bacteria, fungi, protozoa, algae and viruses.
5. Viruses are different from other microorganisms, yet referred to as the microorganism.
6. These microorganisms are helpful economically. They are also used to make many medicines.
7. These microorganisms can be very harmful too as they cause many diseases. Such microbes are called pathogens.
8. Microorganisms are used to enhance the fertility of the soil as they trap the biological nitrogen and fix them in the soil, which in turn is used by plants.
9. Microorganisms work on the dead bodies of the plants and animals to decompose them. They, thus, work as the natural cleansers of the environment.
10. Some microorganisms destroy our food by growing on it. The food infected by these microorganisms become unfit to consume. If consumed it can cause food poisoning.
11. Some special microbes reside in the nodules of the leguminous plants which fix the biological nitrogen from air into soil. The nitrates and nitrites present in soil are further converted into nitrogen gas and released in atmosphere. This whole cycle is called the nitrogen cycle.

Haryana State Board HBSE 8th Class Science Solutions Chapter 1 Crop Production and Management Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 1 Crop Production and Management

HBSE 8th Class Science Crop Production and Management Textbook Questions and Answers

Question 1.
Select the correct word from the following list and fill in the blanks:
Float, water, crop, nutrients, preparation
(a) The same kind of plants grown and cultivated on a large scale at a place is called …………… .
(b) The first step before growing crops is …………… of the soil.
(c) Damaged seeds would …………… on top of the water.
(d) For growing of crop, sufficient sunlight and …………… and …………… from the soil are essential.
Answer:
(a) Crop
(b) preparation
(c) float
(d) water, nutrients.

Question 2.
Match items in column ‘A’ with those in column ‘B’:

Answer:

Question 3.
Give two examples of each:
(a) Kharif Crop
(b) Rabi Crop
Answer:
(a) Paddy and maize
(b) Wheat and gram

Question 4.
Write a paragraph in your own words on each of’the following:
(a) Preparation of soil (b) Sowing (c) Weeding (d) Threshing.
Answer:
(a) Preparation of Soil:
Soil is prepared to sow the seeds. It is tilled to loosen the soil particles for better absorption of water and manures. Loosening of soil particles add humus and nutrition to the soil for better crops. Tilling of soil is done by using ploughs which are pulled by bulls. Tractor driven cultivators are also used to till the soil.

(b) Sowing:
Sowing means implanting the seeds in the prepared soil. Seeds are first selected. Better and healthy breeds of seeds are selected. They are then sowed in the fields with the help of seed drills and funnel shaped tools. The funnel, has a long body on one end of which is placed in soil. Seeds are put in the funnel and seeds go into the soil through long pipe which is carried over in the field with help of ploughs, the lower end pierces through the soil, spreading the seeds. Some seeds are simply spread through the field by hand. Some saplings are planted directly in the field manually.

(c) Weeding:
Unwanted plants growing along the crop are called the weeds. These weeds absorb the nutrients from the soil which are ment for the crops. They are, therefore, removed from the fields. Weeds are either removed manually or by mechanical tools. Certain chemicals are also used to kill the unwanted plants growing in the crops.

(d) Threshing:
Separation of grains from the chaff is called threshing. Seeds are removed from the chaff by threshers. When the crop is harvested, it is cut alongwith the stalks. They are then separated and the grains are removed. This whole process takes place with the help of a huge machine called combine.

Question 5.
Explain how fertilisers are different from manure.
Answer:
Differences between fertilizers and manure:
(i) Fertilisers are chemical substances, while the manures are the organic substances.
(ii) Fertilisers are prepared in the factories while the manures are prepared in fields.
(iii) Fertilisers don’t provide any humus to soil while manures provide a lot of humus.
(iv) Fertilisers are rich in plant nutrients will manures are less rich in plant nutrients.

Question 6.
What is irrigation? Describe two methods of irrigation which conserve water.
Answer:
Watering the crops in the fields is called irrigation. Irrigation is done at different intervals. Irrigation should be done in a way in which water does not get wasted, two such methods which conserve water are:
(i) Sprinklers:
Sprinklers work like fountains. Long perpendicular pipes have holes at regular distances, when water is supplied, it comes out of these holes and spray water in field. These holes have rotating nozzles which sprinkle water in all directions. Limited outflow of water, controls wastage of water.

(ii) Drip System:
This system allows the water to flow drop by drop at the roots of the plants. It contains a main pipe which have further lateral pipes containing small nozzles for the outflow of the water. Nozzles are such placed that they throw water at the roots of the plants, which saves water from flowing around uselessly.

Question 7.
If wheat is sown in kharif season, what would happen? Discuss.
Answer:
If wheat are grown in Kharif season, they would not grow as they do not need ihuch water to grow. The seeds would get destroyed in excess water due to rainy season.

Question 8.
Explain how soil get affected by the continuous plantation of crops in a field.
Answer:
Continuous plantation of crops drains off the nutrients of the soil. It leaves the land unfertile and unable to bear crop. It does not give any time to the soil to replenish the absorbed nutrients by the crops, thus unable to sustain any further healthy and good crop.

Question 9.
What are weeds V How can we control them?
Answer:
Weeds are the unwanted plants growing along crops. They share the nutrients meant for plants and thus are harmful. We can control weeds with the help of chemicals called weedicides. Weeds are the unwanted plants growing along the main crops. They are either removed manually or by chemicals. Weedicides are sprayed in the fields to kill the unwanted plants. These weedicides do not affect the main crop. Weeds are removed or killed during their vegetative phase before flowering or bearing seeds.

Question 10.
Arrange the following boxes in proper order to make a flow chart of sugarcane crop production:

Answer:

Question 11.
Complete the following word puzzle with the help of clues given below:

Down
1. Providing water to the crops.
2. Crop grains have to be kept for a long time in proper conditions.
5. Certain plants of the same kind grown on a large scale.

Across
3. A machine used for cutting the taatured crops.
4. A rabi crop that is also one of the pulses.
6. A process of separating the grain from chaff.
Answer:

Activity 1.3

Extended Learning – Activity And Projects

Question 1.
Sow some seeds in the soil and arrange to water them by drip irrigation. Observe daily.
(i) Do you think it can save water?
(ii) Note the changes in the seed.
Answer:
(i) Yes, drip irrigation saves water as it doe not allow the water to flow on sides and get wasted.
(ii) Seeds slowly get germinated.

Question 2.
Collect different types of seeds and put them in small bags. Attach these bags in a herbarium file and label them.
Answer:
Do it yourself.

Question 3.
Collect new agricultural machine pictures and paste in a file with their names and uses.
Answer:
Tractor to drew ploughs and carriage combines for threshing.
Plough for tilling soil.
Winnowing machine for removing chaff.

4. Project Work: Visit a farm, nursery or a garden nearby. Gather information about:
(i) importance of seed selection
(ii) method of irrigation
(iii) effect of extreme cold and extreme hot wather on the plants
(iv) effect of continuous rain on the plants
(v) fertilisers / manure used.
Answer:
(i) Good seed give good crops.
(ii) Traditional and modern
(a) Traditional: Moat, Chain pumps, Dhekli and Rahat
(b) Modern: Drip irrigation and Sprinklers.
(iii) Extreme cold and heat destroy the crops.

(iv) → Continuous rain get plants decomposedand waer logged in fields.
→ Minerals and fertilisers get flown away.
→ Top fertile layers get destroyed.
(v) Enhance the productivity of soil.

For more information, visit:

• www.krishiworld.com / html / balanced fertiliser.htm.
• www.ikis.com / links / ap.cultivation.html.

HBSE 8th Class Science Crop Production and Management Important Questions and Answers

Very Short Answer Type Questions

Question 1.
Why do every living organism need food?
Answer:
Every living organism needs food to grow and perform various other activities and body functions.

Question 2.
Where do we get our food from?
Answer:
We get our food from plants and animals.

Question 3.
What is agriculture?
Answer:
Growing and managing crops is called agriculture.

Question 4.
What is crop?
Answer:
When same type of plants are grown at a large scale, it is called crop.

Question 5.
Name the factors controlling crop production.
Answer:
Soil, water, sunlight and air.

Question 6.
What are the rainy season crops called?
Answer:
Kharif crops.

Question 7.
What are the summer season crops called?
Answer:
Zayed crops.

Question 8.
What are the winter season crops called?
Answer:
Rabi crops.

Question 9.
Name any three Kharif crops.
Answer:
Paddy, maize, cotton.

Question 10.
Name any three Rabi crops.
Answer:
Wheat, gram, mustard.

Question 11.
Name any three Zayed crops.
Answer:
Moong, musk melon, bitter gourd.

Question 12.
What is tilling?
Answer:
Tilling is the loosening and turning of the soil.

Question 13.
What are crumbs?
Answer:
Crumbs are big pieces of soil present in fields, which require tilling.

Question 14.
Which agricultural tools are Used for tilling?
Answer:
Plough, hoe and cultivators.

Question 15.
Name tools used for sowing.
Answer:
Funnel shaped pipe with plough and seed drill.

Q. 16.
What is transplantation of seeds?
Answer:
Small saplings of plants are directly plantedj in fields. This is called transplantation.

Question 17.
What are fertilizers and manures?
Answer:
Manures and fertilizers are the substances added to soil to enhance its fertility and nutrients.

Question 18.
Which manure is called organic manure?
Answer:
Manure obtained from the dead bodies of plants and animals.

Question 19.
Name any two important fertilizers.
Answer:
Urea, NPK (Nitrogen, Phosphorus, Potassium).

Question 20.
What is a fallow?
Answer:
An uncultivated field between two croppings is called a fallow.

Question 21.
Write sources of irrigation.
Answer:
Wells, tubewells, ponds, lakes, rivers, dams and canals.

Question 22.
What is harvesting?
Answer:
Cutting of the crop after it is mature is called harvesting.

Question 23.
What is threshing?
Answer:
Separating seeds from the chaff is called threshing.

Short Answer Type Questions

Question 1.
What do you mean by agriculture?
Answer:
The term agriculture is derived from the Latin words ‘Ager’ which means field and ‘culture’ which means cultivation. Thus, cultivation in fields means agriculture.

Question 2.
Write the names of various agricultural practices undertaken to produce a crop.
Answer:
Following agricultural practices are performed to produce the crop:
1. Soil preparation
2. Sowing
3. Adding manure and fertilizers
4. Irrigation
5. Protection from weeds
6. Harvesting
7. Storage.

Question 3.
How many categories of crops are sown in India based on the seasons?
Answer:
Three categories of crops are sown in India based on the seasons:
(i) Kharif crops are sown during rains.
(ii) Rabi crops are sown during winters, and
(iii) Zayed crops are grown during summers.

Question 4.
Why is the $oil turned and loosened before seeds are sown?
Answer:
The soil is turned and loosened during the process of ploughing. The ploughing loosens the soil particles and turn the soil of upper

surface. This allows the nutrients from the dead organism to be released back in the soil and better penetration and absorption of nutrients by plant roots.

Question 5.
What are manures and fertilizers?
Answer:
Manures and fertilizers are used to enhance the productivity and fertility of the field. Manure is made of waste products of animals and plants. Fertilizers are chemicals rich in nitrogen, potassium.

Question 6.
What is the role of water in production of crops?
Answer:
Water is essential for all plants. Crops should get enough water at different stages of their growth. Different crops require different amount of water in the field. The wheat crop requires moderate amount of water at the time of sowing, flowering and ripening of crop.
Therefore, corps should be irrigated properly according to their needs.

Question 7.
What are the different methods of irrigation?
Answer:
Different methods of irrigation are adopted according to the requirement of soil and size of the field. Some common methods of water supply are through small channels, which get water from tubewells and canals, lift irrigation, sprinkler, dripping irrigation, etc.

Question 8.
Define weeding. What tools are used for weeding?
Answer:
Weeds are unwanted and undesirable plants which grow alongwith the crop plants in the field. They grow rapidly than the crop plants and cause harm to them. It is, therefore, essential to remove weeds at proper time. The process of removing the weed plants is called weeding. It is done either by hand or by khurpi. It is also done by spraying chemicals or weedicides.

Question 9.
What is humus? How is it formed?
Answer:
Humus is a kind of soil rich in nutrients. It is formed by the microbial action on dead decaying bodies and leaves. It is generally formed on those spots where-there are dense layers of trees. The soil below it becomes dark having more number of pathogenic bacteria.

Question 10.
What are pesticides?
Answer:
The chemicals which are used to protect crops from the organisms called pests are known as pesticides. They are used to kill eggs and larvae of insects who could cause harm to the crops. Pesticides are sprayed in the fields by different methods at different intervals.

Question 11.
What safety measures are to be taken in handling pesticides and weedicides?
Answer:
Insecticides and pesticides are highly poisonous chemicals. They kill the pests. They can harm the humans also. So, certain precautionary measures should be taken while spraying pesticides and weedicides.

They should be kept away from the reach of children.
They should not be inhaled while spraying. Gloves and mouth covers should be used while spraying them.
Hands should be washed properly after their use.

Question 12.
Distinguish between pesticides and weedicides?
Answer:
Weeds are controlled by using certain chemicals called weedicides. These chemicals do not cause any damage to the crop.
Pesticides are the chemicals which are used to kill the pests growing on the crops. They kill the eggs and larvae of the insects.

Question 13.
Explain the process of harvesting?
Answer:
The removal of crop after maturity is called harvesting. The harvesting is done manually with the help of ordinary sickles in crops like wheat, paddy and maize. Even tractor driven machines are also used for harvesting wheat and paddy. Fruits and vegetables are plucked manually.

Question 14.
Explain the process of threshing,
Answer:
The crops need to be threshed to separate grains from the chaff. The mechanical harvesters help in both threshing and separating the grains. The small farmers thresh their crops by spreading the crops on the ground and walking of animals over it. Now-a-days threshing is done by threshing machines driven by tractors or electric motors, which separate grain from chaffs.

Question 15.
What factors influence the crop production?
Answer:
The factors that influence the crop production are as follow:
(i) “Soil: It is the upper layer of earth’s crust. It is the natural medium which supports plant growth.
(ii) Water: Plants require water during various stages of their growth and development such as germination, flowering, ripening, etc.
(iii) Air: Air is essential for breathing and photosynthesis.
(iv) Sunlight: It is essential for plants as a major promotion factor for photosynthesis, germination and flowering.

Question 16.
Suggest ways for the improvement of crops.
Answer:
Following ways should be adopted to improve the crops:
(i) Use of improved seeds.
(ii) Improve fertility of soil.
(iii) Protection against pests and weeds.
(iv) Better transport and storage facility.
(v) Introduction of high yielding varieties of seeds.

Long Answer Type Questions

Question 1.
What are some basic principles of crop production?
Answer:
There are certain conditions which are very important for causing the good crop yield. Good and right kind of soil, seeds, water and protection of crops from weeds and pests as well as the use of proper implements and practices- all go to determine the quality and reliability of crop yield.

A field or farm needs to be managed properly in order to get better yield. Farmers, therefore, must observe some important things which are listed below:
(i) The crop field should be open so that sunlight and air are abundantly available.
(ii) The field should be protected from stray cattle and tresspass which may destroy the crop.
(iii) The soil should be loosened and turned before sowing so that the plant roots can penetrate into it easily and are well ventilated. The latter helps in holding the plant firmly. Root and tuber crop plants need loosened soil for proper growth of the plant product.
(iv) The right amount of water should be available neither too less nor too in excess.
(v) The soil should contain sufficient nutrients for the growth of the plants.
(vi) The unwanted plants such as weeds should be removed from the soil. These weeds compete with the main plants and deprive them of their nourishment.

Question 2.
What is the use of soil for the plants?
Answer:
Soil plays an important role in agriculture in following ways:
(i) Soil fix up the plant in the soil. It holds the roots firmly and anchor the plant.
(ii) Soil has the power of retaining the water which helps the absorption by plants. It also contains minerals etc. which provides food nutrients to the plants.
(iii) It also provides space for living to useful animals such as earthworms which turn up soil and make it fertile.
(iv) Soil holds air in its gaps. This air is used by the plant for its respiration as well as for the respiration of the useful plants and bactria.

Question 3.
How are pests controlled in a crop field?
Answer:
Pests are the organisms smaller bugs which damage the crop plants in the field, during transportation, in the godowns. The common pests are birds, rats and other rodents, some animals, insects and micro-organisms belonging to different groups. They are harmful as they destroy the crop. Pests like locusts, beetles, red spiders, aphids, etc. can be controlled by three methods.
(i) Chemical control: The use of pesticides like DDT, malathion, BHC and aldrin. These chemicals are quick and effective way of controlling the growth of the pests.
(ii) Biological control: One insect feeds von other insect. In this method harmless insects are introduced in the field which will be harmful for insects and other pests.
(iii) Growing pests resistant varieties: Breeding crop varieties which are resistant to pests is a very effective and common method of pest control.

Question 4.
Why do we irrigate our crops? Explain.
Answer:
Water is required by the plants for the following activities:
(i) The seeds sown in the soil absorb water for various activities related to germination, such as activation of phenul, radicle and embryonal axis.
(ii) Water is essential for softening of soil particles so that the roots may penetrate deeply into the soil easily.
(iii) The mineral salts, manure particles, etc. dissolve in water and make the dilute solution. It is easily absorbed by the root hair.
(iv) Water is essential to maintain the turgidity of the cells and to keep them inactive form.
(v) Water is evaporated from the soil as well as from the aerial parts of the plants. Irrigation is essential to fill up the loss of water.
(vi) For the preparation of food by the plants through the process of photosynthesis, water is very essential.

Question 5.
Why an earthworm is called a friend of a farmer?
Answer:
Before sowing seeds every farmer prepares his soil for sowing. He digs the soil. He does tilling with help of tractors and ploughs. This all is done to loosen the soil particles so that air .and nutrients can be easily absorbed. Earthworm is an organism which lives under the soil and make burrows for itself. This burrowing action loosens the soil for better penetration of roots of the crops.

It create channels through the field which improves the physical properties of the soil. The burrowing action of earthworm improves soil structure, helps in formation of humus mix and till the soil and increase the supply of nutrients of the plants.

Question 6.
Write a short note of thresting and winnowing.
Answer:
When a farmer cut his crops, he has to separate the grains from the crop it is done in two ways. Manually and with machines.

The separation of seed from the crops by beating out the seeds (grain) from the crop is called threshing. It is done manually or by using threshers with combines.

After separating the grain from the harvested crop, it is required to separate grain from chaff. This process is done by winnowing. The grains are thrown from the height in the direction of air. The air carries away the lighter chaff or dried stems and leaves and the heavier grains drop down in form of a heap. This whole process is called winnowing.

Crop Production and Management Class 8 HBSE Notes

1. All living beings need food to live and perform various other activity.
2. We get food from plants and animals. The plant food is grown in fields making use of various processes. This is called agriculture.
3. All plants of same types grown together are called crops. Different types of crops are grown in the fields e.g. cereals (wheat, paddy rices) fruits and vegetables, etc.
4. Based on seasons many crops are grown. Rainy season crops are called Kharif. Winter crops are called Rabi and Summer crops are called Zayed crops.
5. To grow a crop a number of activities has to be performed. These are called agricultural practices. These agricultural practices include: soil preparation, sowing, adding manure and fertilizers, irrigation, protection from weeds, harvesting, storage, etc.
6. Preparation of soil includes loosening soil. This is called tilling or ploughing. Plough, cultivator and hoe are used as tools.
7. Sowing means putting the seeds in the loosened ground to grow.
8. For a healthy and good crop manure and fertilizers are added to the crop. These are chemicals which enhance the crop production.
9. When we grow crop in the field it takes all the nutrition away from the soil. This nutrition is – required for the next crop. The soil is replenished with nutrition by these fertilizers and manures. Crop-rotation is another method of replenishing nutrition in soil.
10. Crops are watered sufficiently by canals, drips and rainwater. This is called irrigation of crops. Irrigation is the most important process of crop production.
11. Undesirable plants growing among the crops are removed manually or by machines. These unwanted plants are called weeds, chemicals used to kill weeds are Called weedicides.
12. Sometimes some small animals start eating the crops. These are called pests. Special chemicals
are sprayed on the crops to kill the pests. These chemicals are called pesticides.
13. After the crops are ready, they are harvested. Grains are separated from the chaff. This process is called threshing. Threshers are used to do this process.
14. The harvested grains are then Stored in huge stores, after they are properly dried in sun. These stores kre called granaries.
15. We also get our food from animals. For this purpose some useful animals are domesticated
and reared. This is called Animal Husbandry. Animals like cows, buffaloes, goats, hens etc. are domesticated for food.

Haryana State Board HBSE 7th Class Science Solutions Chapter 9 Soil Textbook Exercise Questions and Answers.

Haryana Board 7th Class Science Solutions Chapter 9 Soil

HBSE 7th Class Science Soil Textbook Questions and Answers

Tick the most suitable answer in questions 1 and 2.

Question 1.
In addition to the rock particles, the soil contains:
(i) air and water,
(ii) water and plants
(iii) minerals, organic matter, air and water
(iv) water, air and plants.
Answer:
(iii) minerals, organic matter, air and water.

Question 2.
The water holding capacity is the highest in:
(i) sandy soil
(ii) clayey soil
(iii) loamy soil
(iv) mixture of sand and loam
Answer:
(iii) loamy soil.

Question 3.
Match the items in column I with those in column II:

Answer:

Question 4.
Explain how soil is formed.
Answer:
Soil has been formed from parent rock material over millions of years. The process by which soil formation takes place is called weathering. Weathering is a very slow and gradual process during which parent rock material breaks down into fine particles.

The agents which bring about weathering are many. These are described below:
1. Temperature changes:
Rocks expand when heated and contract when cooled. The hot sun causes the surface layers of rocks to expand more than the layers deeper down. These changes cause the rock surface to break apart.

2. Frost:
Rainwater may become trapped in small crevices of the parent rock. In winter, this water freezes to ice. The ice expands producing a lateral pressure, causing the crevices in the rocks to further open up.

3. Water:
Continual movement of rain and river water, in liquid form, causes breaking down of rock particles into finer particles through their abrasive effect.

4. Wind:
Wind blowing across a rock surface also has a abrasive effect on the rocks. Minute rock particles are carried away by the blowing wind and deposited elsewhere.

Question 5.
How is clayey soil useful for crops?
Answer:
Clayey soils are very useful for crops, because these soils:
(i) contain humus, providing fertility to the soil
(ii) hold sufficient water due to the presence of smaller particles, and
(iii) contain enough air due to the presence of some large particles alsy.

Question 6.
List the differences between clayey soil and sandy soil.
Answer:
Clayey soil:
Clayey soil contains more than 50% of clay particles. Since the clay particles are very small in size, they are very tightly packed and do not allow water to drain out easily. It is poorly aerated because the tightly bound clay particles leave little space in between to trap air. Clayey soil is very sticky and thus tilling the soil is very difficult. However, it is rich in minerals which makes it suitable for plant growth. Due to the great binding capacity of its particles, clayey soil is used for making toys and pots.

Sandy soil:
Sandy soil contains about 60% of sand particles with small amounts of silt and clay. It is very porous and its water holding capacity is very low as all the water easily runs down through the large pores. This type of soil is, therefore, not good for the growth of plants. It is found mainly in the deserts.

Question 7.
Sketch the cross section of soil and label the various layers.
Answer:
Soil profile

Question 8.
Razia conducted an experiment in the field related to the rate of percolation. She observed that it took 40 min for 200 mL of water to percolate through the soil sample. Calculate the rate of percolation.
Answer:
Formula: Percolation rate
\((\mathrm{mL} / \mathrm{min})=\frac{\text { amount of water }}{\text { percolation time }(\mathrm{min})}\)
= \(\frac{200 \mathrm{~mL}}{40 \mathrm{~min}}\)
= 5 mL /min.

Question 9.
Explain how soil erosion could be prevented.
Answer:
Prevention of soil erosion can be brought about by controlling the factors which cause soil erosion. The methods would, thus, be as follows:
1. Deforestation should be stopped. Rather, trees should be planted (afforestation). Afforestation should be undertaken not only in areas already cut, but additional areas should be brought under plantation.

2. To reduce the effect of strong winds in the fields, the boundaries of the fields should be planted with trees in two to three rows.

3. To maintain the soil in its natural condition, it is advisable to grow different crops. Crops rotation, as it is called, helps to maintain the fertility of the soil. The water-holding capacity of the soil is also maintained by this method.

4. Proper drainage and irrigation arrangements should be made in the fields.

5. On the sloping areas in hills, strip cropping should be practised, thereby reducing the steepness of the slopes and checking soil erosion.

Question 10.
Solve the following crossword puzzle with the clues given:

Across:
2. Plantation prevents it.
5. Use should be banned to avoid soil pollution.
6. Type of soil used for making pottery.
7. Living organism in the soil.

Down:
1. In desert soil erosion occurs through.
3. Clay and loam are suitable for cereals like.
4. This type of soil can hold very little water.
5. Collective name for layers of soil.
Answer:

Extended Learning – Activities And Projects

Question 1.
Boojho would like to know the difference between raw and baked soil? Investigate how the soil from which matkas are made is different from the soil used to make status.
Answer:
Do yourself. Take help your teacher.

Question 2.
Paheli is worried. She could see a brick kiln from her house. Bricks were being made there. There was so much smoke coming out of the kiln. She was told that the best quality of clay is required for making pottery, statues and bricks. She has seen truck loads of bricks being taken away for construction of buildings. At this rate, she fears, no soil will be left. Are her fears justified? Discuss this problem with your parents, teachers and other experts of your area and prepare a report.
Answer:
Do yourself.

Question 3.
Try to find out the moisture content of a soil sample. One method is given here.
Activity: Take lOOg soil. (Take help from any shopkeepers to weigh the soil). Place it on a newspaper in the sun and allow it to dry for two hours. This activity is best done in the afternoon. Take care that the soil does not spill outside the newspaper. After drying it, weigh the soil again. The difference in the weight of the soil before and after drying gives you the amount of moisture contained in 100 g of soil. This is called the percentage moisture content.
Suppose your sample of soil loses 10 g on drying. Then
Percent of moisture in soil
= \(\frac{\text { wt. of moisture }(\mathrm{g})}{\text { Original wt. of soil sample }(\mathrm{g})} \times 100\)
In this example
Percent of moisture in soil
= \(\frac{10 \times 100}{100}=10 \%\)
Answer:
Do yourself.

HBSE 7th Class Science Soil Important Questions and Answers

Very Short Answer Type Questions

Question 1.
Define soil.
Answer:
Soil is uppermost layer of earth’s crust, in which plants grow.

Question 2.
Define weathering.
Answer:
Soil is formed from the parent rock material by a very slow and gradual process called weathering.

Question 3.
What is humus?
Answer:The rotting dead matter in the soil is called humus.

Question 4.
Where do plants grow?
Answer:
Plants grow in the soil.

Question 5.
Where does food that helps to sustain and grow, come from?
Answer:
Plants.

Question 6.
How old is our earth?
Answer:
Our earth came into existence about 4.5 billion years ago.

Question 7.
Name the part of the environment which supports life.
Answer:
1. Lithosphire
2. Hydrosphere
3. Atmosphere.

Question 8.
Give one term for the following,
“Removal of top soil by air and water.”
Answer:
Soil erosion,

Question 9.
What do you understand by the term soil conservation?
Answer:
Prevention of soil erosion is called soil conservation.

Question 10.
What is soil pollution?
Answer:
When the structure and properties of the soil are changed by adding unwanted and harmful substances, it is called as soil pollution.

Question 11.
Name two soil pollutions.
Answer:
(i) Insecticides and herbicides
(ii) Industrial wastes like plastic, chemicals, flyash, leather etc.

Question 12.
How soil erosion takes place?
Answer:
When the over grazing or cutting of trees take place the top soil becomes soft and loose which is easily blown by wind and water.

Question 13.
How is soil formed?
Answer:
Soil is formed by cracking of rocks due to contraction and expansion by cooling and heating effect.

Question 14.
What is mineral?
Answer:
Minerals are the non-renewable natural resources.

Question 15.
Name four animals that live in the soil.
Answer:
Bacteria, Earthworm, Snakes, Rats, Ants.

Question 16.
What do you understand by deforestation?
Answer:
When the trees of the forest are cleared to convert the forest land into formland is called deforestation.

Question 17.
State two major problems caused by excessive deforestation.
Answer:
(i) Due to excessive deforestation there is less rain.
(ii) Soil erosion takes place.

Question 18.
Name the materials present in fertile soil.
Answer:
Fertile soil contains nitrates, phosphates, water soluble salts and carbonic acids.

Question 19.
What is crumb?
Answer:
The main skeleton of a fertile soil is called crumb.

Question 20.
What, is the function of air in soil?
Answer:
(i) Air helps, 1:he plants present in the soil in respiration.
(ii) It helps in making soil soft and light in weight.

Question 21.
Which soil horizon is rich in humus?
Answer:
The uppermost layer is called the A- horizon is rich in humus.

Question 22.
Which type of soil is best suited for growth of plants?
Answer:
Loamy soil.

Question 23.
Name the different types of particles present in soil.
Answer:
Soil consists of soil particles, humus (organic matter), water, air and living organisms.

Question 24.
What is strip, cropping?
Answer:
Strip cropping means the planting of crops in rows or strips to check flow of water.

Question 25.
What are loams?
Answer:
Soils having mixtures of different sized particles are called loams or loam soils.

Short Answer Type Questions

Question 1.
What are the components of soil?
Answer:
Some of the main components of soil are as follows:
(i) Humus
(ii) Minerals
(iii) Water
(iv) Air and
(v) Micro organisms 7 bacteria, fungi, insects, larvae and many other organisms.

Question 2.
Write the importance of Humus.
Answer:
Humus is very important for the proper growth of the plants. It helps in growing plants in the following ways:
(i) It makes the soil fertile.
(ii) It allows the roots of plants to penetrate in the soil easily.
(iii) Water and air can pass into it easily,
(iv) It retains water for a longer period.
(v) It binds the soil particles.

Question 3.
What is meant by term wehtherifig?
Answer:
The cooling and heating of rocks cause cracking. They bring about further breaking. This process of breaking the parent rock into fine particles is called weathering.

Question 4.
Describe the harmful effects of deforestation.
Answer:
Deforestation causes the following harmful effects:
(i) Soil erosion will take place.
(ii) There will be draught due to which famine will occur. .
(iii) There will be less rain.
(iv) There will be excess amount of CO, due to which Green House effect will take place. It may cause flood in-the rivers.

Question 5.
Why biosphere supports life?
Answer:
Biosphere has all those requirements such as air, water, minerals, sunlight etc. which are essential for the survival of living things.

Question 6.
What are natural resources?
Answer:
Natural resources are those which are provided by nature to support life. Such as water, air, minerals, sunlight and various life forms.

Question 7.
What is soil erosion?
Answer:
The top soil being soft and light is carried away easily by wind and water, the natural agents. This process of removal of soil is called soil erosion.

Question 8.
Distinguish between residual and transported soils.
Answer:
Residual soils are those in which the whole process of soil formation, i.e., weathering and development of soil profile occurs at the same place. In these soils, the soil is formed at the place where the parent rock is present.

Transported soils are those where the v weathered soil particles are taken away to other places. This is done by several agents.

Question 9.
State any four major advantages of forests.
Answer:
Forest is a natural renewable resource which is advantageous in the following ways:
(i) It creates a suitable environment for rain.
(ii) It helps in controlling the soil erosion.
(iii) It absorbs excess rain water as subsoil water.
(iv) It provides the home to variety of animals.

Question 10.
What is the importance of soil organisms?
Answer:
A number of organisms such as earthworms, bacteria, fungi and round- worms are found in the soil.
Soil organisms are important because of various uses:
1. As you know, earthworms burrow the soil, swallow it and make it loose and soft.
2. Micro-organisms cause the decomposition’ of dead plants and animals, and release the minerals back of the soil. The minerals can again be absorbed by the plant roots. Mineral cycling goes on in this manner.
3. Some bacteria are able to fix nitrogen in association with roots of legume plants like pea and gram.

Long Answer Type Questions

Question 1.
How is soil important to us? Explain.
Answer:
Our mother Earth is blessed with immense land resource. It is valuable to man for food production. It is also a basic part of wildlife habitats and recreational resources. Various soil organisms like earthworms, bacteria, insects and mammals use this as a natural habitat. Plants obtain water and minerals through this land resource. Plant sources of many medicinal drugs exist here. Wood fibres, fruits, rubber, oils, dyes and various other economic products which the man uses, are all dependent on this land. The very existence of mankind is greatly influenced by this land resource.

Question 2.
Describe the factors which cause soil erosion.
Answer:
Soil erosion is the removal of topsoil. This is brought about by wind and water or rain. There are several factors which allow water and wind to cause soil erosion. Some of these factors are:
(i) Deforestation:
Cutting down of trees and excessive farming are practices that destroy vegetation and expose land to the action of wind and water. Water runs off the soil surface with great speed and carries the soil particles into rivers which get chocked with silt resulting in floods. This problem assumes alarming proportions on hills.

(ii) Overgrazing:
Overgrazing by animals also destroys vegetation making land barren. The top soil on barren land can then be eroded by water and wind.

(iii) Poor methods of farming:
Tilling or ploughing loosens the soil which can then be easily eroded by wind and water. Due to excessive farming the layer of humus gets depleted and water holding capacity of the soil also reduces. The topsoil thus dries up and can be carried away by wind and water.

(iv) Forest fires, too, lead to soil erosion. After fire, the soil is exposed to two main factors causing erosion, namely wind and water.

Question 3.
Write short notes on the importance of the following:
(а) Soil, (b) Forests, (c) Soil organisms, (d) Overgrazing, (e) Earthworms.
Answer:
(a) Soil:
(i) Soil provides shelter to several micro-organism and some macro- organisms.
(ii) All the plants grow in it.
(iii) It acts as store-house of minerals.
(iv) It acts as raw material for building bricks, mortar, pottery, pulp for paper industry is. obtained from plants grown in the soil.
(v) It acts as water storage.
(vi) It provides employment.

(b) Forests: Forests are very useful to man-kind in the following ways:
(i) It maintains the balance of gases in the atmosphere.
(ii) It causes rain.
(iii) It provides the shelter to the wild animals.
(iv) It provides the valuable things like timber, honey, bee wax, lac, medicines.

(c) Soil Organisms:
Various micro organisms live in the soil which make the soil porous, soft and airy. They make soil fertile. They convfert manure into simple form which can be used by plants of the forest.

(d) Overgrazing:
When the cattle , eat grass of l^rge area, it is called as overgrazing. This process makes the soil plain which can be used for industrialisation and urbanisation.

(e) Earthworm:
Earthworms are the friends of the farmer. They eat dead organicv substances along with the soil and convert them into simple soluble forms which make the soil fertile and soft.

Question 4.
Describe the composition of soil.
Answer:
Composition of soil varies from place to place. It depends on the type of rock from which it is formed. However, all soils contain the following components:
(i) Rock particles: Tiny particles of soil derived from the parent rock.
(ii) Humus: Humus consists of decaying remains of plants and animals.
(iii) Living organisms: Soil contains a large number of micro-organisms like bacteria, algae, fungi and protozoa. Many small animals like insects, earthworms, spiders, scorpions, centipedes and millipedes are found in the soil. Burrowing animals like rats, moles, rabbits and guinea pigs make tunnels in the soil.
(iv) Water: Water is present in pores between soil particles and helps the plants in their growth.
(v) Air: Air is also present in the soil pores and is essential for the survival of living organisms present in the soil.

Question 5.
What is soil pollution? What are the major sources of soil pollution?
Answer:
Any substance that adversely affects the, productivity of soil is called a soil pollutant. Contamination of soil with pollutants like insecticides, artificial fertilizers and industrial wastes is called soil pollution. The major sources of soil pollution are:
(i) Pollutants like acids washed off from the atmosphere (acid rain).
(ii) Pesticides and herbicides sprayed in fields.
(iii) Excessive use of artificial fertilizers.
(iv) Solid wastes like garbage, trash, ash, building material, plastic bottles and cans.

Soil Class 7 HBSE Notes

1. Soil is the uppermost layer of earth’s crust, in which plants grow.
2. Soil is formed from the parent rock material by a very slow and gradual process called weathering. A number of agents temperature changes, frost, water, wind and living organisms – are involved in the weathering of rocks.
3. Six types of soil are mainly found in India – Red soil, black soil, alluvial soil, desert soil, mountain soil and laterite soil. Humus content is maximum in mountain soil. Black soils are rich for growing cotton and sugarcane while alluvial soil is suitable for wheat and rice.

4. There are three main layers or horizons in the soil profile – A-horizon (top soil), B horizon (subsoil) and C-horizon (parent rock).
5. Soil consists of soil particles, humus (organic matter), water, air and living organisms.
6. Soil particles, depending on size, consist of clay (below 0.002 mm), silt (0.002 to 0.02 mm), sand (0.02 to 2.0 mm) and gravel (above 2.0 mm).
7. A soil containing a mixture of sand, silt and clay is called a loamy soil. It is the best soil for plant growth.
8. Soil is an important natural resource. It provides us food, clothing, shelter, medicines,
rubber, dyes and a number of other useful products. Besides man, it provides shelter to wildlife and different soil organisms.
9. Wind and rain bring about loss of the top soil (soil erosion). Deforestation, over grazing and poor farming methods have accelerated the process of soil erosion.
10. Prevention of soil erosion (soil conservation) can be brought about by growing plants (afforestation), crop rotation, prevention of overgrazing maintaining proper drainage, and growing crops in rows or strips in the hills (strip-cropping).

Haryana State Board HBSE 7th Class Science Solutions Chapter 8 Winds, Storms and Cyclones Textbook Exercise Questions and Answers.

Haryana Board 7th Class Science Solutions Chapter 8 Winds, Storms and Cyclones

HBSE 7th Class Science Winds, Storms and Cyclones Textbook Questions and Answers

Question 1.
Fill the missing word in the blank spaces in the following statements:
(a) Wind is …………… air.
(b) Winds are generated due to …………… heating on the earth.
(c) Near the earth’s surface air rises up whereas …………… air comes down.
(d) Air moves from a region of …………… pressure to a region of …………… pressure.
Answer:
(a) moving
(b) uneven
(c) warm, cooler
(d) high, low.

Question 2.
Suggest two methods to find out wind direction at a given place.
Answer:
(i) Take a piece of a paper in your hand. Let it fall from your hand. It will blow in the direction in which wind is blowing.
(ii) You can use a wind vane (a device helps us to make accurate measurements of wind direction) to find out the direction of wind.

Question 3.
State two experiences that made you think that air exerts pressure (other than those given in the text).
Answer:
(i) Balloons and balls can be used only when they are inflated with air.
(ii) Compressed air is used in the brake system for stopping trains.

Question 4.
You want to buy a house. Would you like to buy a house having windows but no ventilators? Explain your answer.
Answer:
No. A house which has no ventilators is not a healthy house to live in. The air circulation is not there in such a house and hence it has no fresh air.

Question 5.
Explain why holes are made in hanging banners and hoardings.
Answer:
Air exerts pressure. It is due to this pressure banners and hoardings flutter when the wind is blowing. Holes are made in the banners and hoardings as wind pass through that holes and they does not become loose and fall down.

Question 6.
How will you help your neighbours in case cyclone approaches your village/town?
Answer:
(i) A cyclone forecast and warning service.
(ii) Rapid communication of warnings to the Government agencies, the ports, fishermen, ships and to the general public.
(iii) Construction of cyclone shelters in the cyclone prone areas, and Administrative arrangements for moving people fast to safer places.

Question 7.
What planning is required in advance to deal with the situation created by a cylone?
Answer:
In order to deal with cyclone, it is important to follow the following points:
(i) listening carefully to warnings being transmitted on TV and radio.
(ii) moving to safer places or taking adequate steps to ensure safety at home.
(iii) keeping an emergency kit ready.
(iv) storing food in water-proof bags.
(v) not venturing into sea.
(vi) keeping all the emergency numbers handy.

Question 8.
Which one of the following place is unlikely to be affected by a cyclone?
(i) Chennai
(ii) Mangalore
(iii) Amritsar
(iv) Puri
Answer:
(iv) Puri.

Question 9.
Which of the statements given below is correct?
(i) In winter the winds flow from the land to the ocean.
(ii) In summer the winds flow from the land towards the ocean.
(iii) A cyclone is formed by a very high pressure system with very high speed winds revolving around it.
(iv) The coastline of India is not vulnerable to cyclones.
Answer:
(i) In winter the winds flow from the land to the ocean.

Extended Learning – Activities And Projects

Question 1.
You can perform the Activity 8.5. in the chapter at home slight differently at home. Use two plastic bottles of the same size. Stretch one balloon on the neck of each bottle. Keep one bottle in the sun and the other in the shade. Record your observations. Compare these observations and the result with those of Activity 8.5.
Answer:
Do yourself.

Question 2.
You can make your own anemometer. Collect the following items:
4 small paper cups (used ice-cream cups), 2 strips of cardboard (20cm long and 2cm wide), gum, stapler, a sketch pen and a sharpened pencil with eraser at one end.
Take a scale; draw crosses on the cardboard strips as shown in the Fig. 8.4. This will give you the centres of the strips.

Finding centre of the strips

A model of an anemometer
Fix the strips at the centre, putting one over the other so that they make a plus (+) sign. Now fix the cups at the ends of the strips. Colour the outer surface of one cup with a marker or a sketch pen. All the 4 cups should face in the same direction.

Push a pin through the center of the strips and attach the strips and the cups to the eraser of the pencil. Check that the strips rotate freely when you blow on the cups. Your anemometer is ready. Counting the number of rotations per minute will give you an estimate of the speed of the wind. To observe the changes in the wind speed, use it at different places and different times of the day.

If you do not have a pencil with attached eraser you can use the tip of a ball pen. The only condition is that the strips should rotate freely.
Remember that this anemometer will indicate only speed changes. It will not give you the actual wind speed.
Answer:
Do yourself.

Question 3.
Collect articles and photographs from newspapers and magazines about storms and cyclones. Make a story on the basis of what you learnt in this Chapter and the matter collected by you.
Answer:
Do yourself.

Question 4.
Suppose you are a member of a committee, which is responsible for creating development plan of a coastal state. Prepare a short speech indicating the measures to be taken to reduce the suffering of the people caused by cyclones.
Answer:
Do yourself.

Question 5.
Interview eyewitness to collect the actual experience of people affected by a cyclone.
Answer:
Do yourself.

Question 6.
Take an aluminium tube about 15 cm long and 1 to 1.5 cm in diameter. Cut slice of a medium sized potato about 2 cm thick. Insert the tube in the slice, press it, and rotate it 2-3 times. Remove the tube. You will find a piece of potato fixed in the tube like a piston head.

Repeat the same process with the other end of the tube. Now you have the tube with both ends closed by potato pieces with an air column in between.

Take a pencil with one end unsharpened. Place this end at one of the pieces of potato. Press it suddenly to push the potato piece in the tube. Observe what happens. The activity shows rather dramatically how increased air pressure can push things.
Caution: When you perform this activity, make sure that nobody is standing in front of i e tube.
Answer:
Do yourself.

HBSE 7th Class Science Winds, Storms and Cyclones Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is a wind?
Answer:
The moving air is called wind.

Question 2.
Define the term ‘cycle’.
Answer:
It is an event or phenomenon which repeats itself after sometime.

Question 3.
Define term ‘evaporation’.
Answer:
The process of changing water from its liquid form to its vapour is known as evaporation.

Question 4.
Is evaporation a slow process or fast process?
Answer:
Evaporation is a slow process.

Question 5.
Name two processes through which water vapour add continuously into the air.
Answer:
The two processes are:
(i) Evaporation
(ii) Condensation.

Question 6.
Define condensation.
Answer:
The process of conversion of water vapours into liquid form of water is called condensation.

Question 7.
Define water cycle.
Answer:
The water in its vapour form goes into air by evaporation and transpiration forms cloud and, then comes back to the surface of the earth through the process of condensation and precipitation. This process is called ‘water cycle’.

Question 8.
At what speed wind becomes (i) gentle breeze, (ii) storm?
Answer:
When the wind blows gently, it is called a breeze. But, when it blows very fast it causes storm.

Question 9.
What is sea breeze?
Answer:
In coastal areas, during the day, the cool air blows from sea towards the land called sea breeze.

Question 10.
What is land breeze?
Answer:
In coastal areas, during the night, the cool air blows from land to sea called the land breeze.

Question 11.
What is tornadoes?
Answer:
In our country tornadoes are not very frequent. A tornado is a dark funnel shaped cloud that reaches from the sky to the ground.

Question 12.
What is ‘hurricane’?
Answer:
The ‘hurricane’ is the term used for storm in America and West Indies.

Question 13.
What is the eye of hurricane?
Answer:
The region of chimney like low pressure around which warm water vapour spirals is called the eye of hurricane.

Question 14.
What is Beaufort Scale?
Answer:
The number and name of.a wind is determined by the speed at which it flows on an internationally accepted scale, called Beaufort scale.

Question 15.
Name two properties of air.
Answer:
(i) Air occupies space
(ii) It has mass.

Question 16.
Write two importances of air in agriculture.
Answer:
(i) Air helps rotate wind-mill which is used to draw water from tube-wells.
(ii) Air helps in dispersion of seeds and pollen grains of flowers of several plants.

Question 17.
How are high building protected from lightning?
Answer:
High buildings are protected from lightning by fixing lightning conductor on the building.

Question 18.
What is the cause of atmospheric electricity?
Answer:
Atmospheric electricity is due to ionisation of air by the ultraviolet rays of sunlight.

Question 19.
Is our body a conductor?
Answer:
Yes, our body is a good conductor of electricity.

Question 20.
What damage can lightning do?
Answer:
Lightning damage the high buildings and the trees on which it strikes. The buildings and trees can be set on fire by lightning. It can do a high loss of life and property.

Question 21.
Why do chimneys made of steel not require lightning conductor?
Answer:
Steel is a good conductor of electricity. Due to this reason steel chimneys do not require lightning conductor. They themselves pass the discharge to the earth.

Question 22.
Why is it advised not to take shelter under a tree during lightning?
Answer:
We should not stand under a tree during lightning, due to the danger of the lightening, because it can destroy the trees and can set it on fire.

Question 23.
Which gas is produced in air during lightning that absorbs ultraviolet radiation present in sunlight?
Answer:
During lightning ozone (oz) gas is produced due to higher temperature which absorbs ultraviolet radiation. It is dangerous for the living being.

Question 24.
Name the arrangement used for the protection of buildings against damage from lightning.
Answer:
To protect buildings from damage by lightning, a good lightning conductor is used. This is done by installing a lightning conductor on the buildings.

Short Answer Type Questions

Question 1.
How is rain caused?
Answer:
Water, on land, is present in different sources, e.g., sea, river, pond, lake, etc. The water from all these sources change into vapour form due to sun’s heat and goes up into the air. This change of water into vapour form is called evaporation. The water vapour, when reaches high up in the air, cools down and forms clouds. This cooling down of water vapour to form clouds is called condensation. On cooling, the water vapour changes to water droplets. These group together farm clouds. When the droplets become very heavy they fall down as rain.

Question 2.
What is water cycle? What does it indicate?
Answer:
Evaporation of water from oceans, ponds, rivers, lakes and from roads and streets to form cloud by condensation at higher altitude. When clouds rain, the rain water flows into the seas and oceans through rivers and streams. Some water percolates into the soil to form underground water. It comes again out in the form of spring and well. This is called water cycle.

Because of water cycle, the amount of water on the earth remains more or less the same. The water cycle also indicates that all the water in world is on the move all the time.

Question 3.
How does water cycle help in maintaining global climate?
Answer:
Water cycle plays an important role in the world climate. Oceans absorb vast quantities of heat and help in global warming. By absorbing heat water evaporates and on condensation releases heat. This absorption and releasing of heat in the form of energy drives weather pattern in the short term and regulate the climate for long time.

Question 4.
How is storm caused?
Answer:
When the wind blows gently, it is called a breeze. But, when it blows very fast it causes storm. Storm may be defined as something taking place in the weather of a violent nature. At sea, a storm may be a strong wind or gale. On land, a storm usually means a weather situation marked by heavy rain and often with strong winds, lightning and thunder.

Question 5.
How a thunderstorm becomes a cyclone?
Answer:
Water requires heat when it changes from liquid to vapour state. Before cloud formation water takes up heat from the atmosphere to change into vapour. When water vapour changes back to liquid form as raindrops, this heat is released to the atmosphere. The heat released to the atmosphere warms the air around. The air tends to rise and causes a drop in pressure. More air rushes to the centre of the storm. This cycle is repeated. The chain of events ends with the formation of a very low pressure system with very high speed winds revolving around it. It is this weather condition that we call a cyclone.

Question 6.
How is lightning useful in nature?
Answer:
Lightning is useful in nature because during lightning intense heat and high temperature are produced. As a result, nitrogen combines with oxygen to form its oxides. These oxides of nitrogen further get dissolved in water to form a dilute solution of nitric acid that comes to the ground with rain. This is how nature provides nitrogenous compounds to plants that are important for their growth.

Question 7.
How is ozone layer useful for us?
Answer:
During lightning, a part of oxygen gets converted to ozone. Ozone provides protection against harmful ultraviolet radiations of the sun that cannot reach the earth’s surface.

Question 8.
What are the precautions to be taken against a storm is accompanied by lighting?
Answer:
If a storm is accompanied by lightning, we must take the following precautions:
(i) Do not take shelter under an isolated tree. If you are in a forest take shelter under a small tree. Do not lie on the ground.
(ii) Do not take shelter under an umbrella with a metallic end.
(iii) Do not sit near a window. Open garages, storage sheds, metal sheds are not safe places to take shelter.
(iv) A car or a bus is a safe place to take shelter.
(v) It you are in water, get out and go inside a building.

Question 9.
Why is it advisable to switch off TV sets during lightning?
Answer:
Lightning in the sky also effects radio and TV transmission in our radio and TV sets during lightning and thunder is due to this reason. TV antina and dish antina has fixed on tall buildings are especially prove to lightning strikes. So it is advisable to stop our TV set during lightning to save them from damage.

Question 10.
What is a lightning conductor? Why is it fixed on the top of high tall buildings?
Answer:
A lightning conductor is a long flat thick strips of copper with sharp point or spikes. The lower end of it is connected to copper plate deep into the earth. It is fixed on the top of the building because the thundering electricity comes in the contact first and the building will not be damaged.

Question 11.
How are lightning and thunder caused?
Answer:
When two oppositively charged clouds are near each other, the air between them becomes good conductor because charges begin, to move in air very speedily. The presence of electric charges in very large quantities in the air causes to appear as steaks of lightning and thunder.

Question 12.
When do we say that lightning has struck on the earth?
Answer:
Sometimes the direction of the wind changes; then the clouds move and the charges in the clouds are discharged into the earth when it happens, then it is said that lightning has struck on the earth.

Question 13.
Why should we not stand under a tree during a thunderstorm?
Answer:
We should not stand under a tree during a thunderstorm due to the danger of the lightning because it can destroy the tree, and can set it on fire.

Question 14.
What are tornadoes?
Answer:
In our country tornadoes are not very frequent. A tornado is a dark funnel shaped cloud that reaches from the sky to the ground. Most of the tornadoes are weak. A violent tornado can travel at speeds of about 300 km/h. Tornadoes may form within cyclones.

Question 15.
Write short note on ‘lightning conductor’.
Answer:
A lightning conductor is made up of long, thick metal rod having sharp spikes at its upper end. The spikes pointing towards the sky are fixed at the highest points of the building. The lower end of the metal rod is connected to a large copper or aluminium plate which is hurried deep inside the earth which is called earthing.

When a highly charged cloud passes over a tall building, it induces an opposite charge on the spikes. This charge quickly flows to the earth through the copper rod. Hence, the lightning discharge is prevented and the building is saved from damage.

Question 16.
Explain how lightning takes place?
Answer:
Normally air is a bad conductor of electricity. However, when two clouds having huge amount of positive and negative state charges approach each other, the air becomes a good conductor of electricity.

Thus the electrons from the negatively charged cloud push their way through air so as to reach the positively charged cloud. In doing so the air gets white hot and hence a dazzling bluish white streak of light is formed which is called lightning.

Question 17.
What precautions should be taken to provide protection against lightning?
Answer:
Precautions should be taken to provide protection against lightning:
Answer:
(i) Lightning conductor provides us a simple means to protect against damage due to lightning property and life.
(ii) When lightning strikes, it provide a path to the entire charge through it to the earth.
(iii) We should not stand under, I tree during a thunderstorms due to the air of lightning, because it destroys trees set it on fire.
(iv) Lightning conductor should be installed on large buildings and tall chimneys of factories.

Long Answer Type Questions

Question 1.
Describe water cycle in nature.
Answer:
Water constantly moves from the earth to the air and back again.
The constant circulation of water is known as the water cycle.

The water in seas, rivers, lakes, ponds or streams evaporates because of the heat of the sun.

Plants also give out large amounts of water from their leaves. The water vapour rises up. The air higher up in the atmosphere is cooler. This cools the water vapour and it condenses to form tiny drops of water on dust particles. These drops of water together form clouds. As the clouds get cooled further, the water drops become bigger and heavier. When they become too heavy, they fall to the earth as rain. The rain water enters the seas, rivers, lakes, ponds and streams and then evaporates again. Thus the water cycle in nature goes on.

Question 2.
Explain destructions caused by cyclones.
Answer:
Cyclones can be very destructive. Strong winds push water towards the shore even ;f the storm is hundreds of kilometres away. These are the first indications of an approaching cyclone. The water waves produced by the wind are so powerful that a person cannot overcome them.

The low pressure in the eye lifts water surface in the centre. The rising water may be as high as 3-12 metres. It appears like a water wall moving towards the shore. As a result the seawater enters the low-lying coastal areas, causing severe loss of life and property. It also reduces the fertility of the soil.

Continuous heavy rainfall may further worsen the flood situation. High speed winds accompanying a Cyclone can damage houses, telephones and other communication systems, trees, etc; causing tremendous loss of life and property.

Question 3.
What is lightning? How does ligthning takes place in the clouds?
Answer:
When the air gets white hot and hence a dazzling bluish white streck of light is framed, is called lightning. Normally air is a bad conductor of electricity. However, when two clouds having J e amount of positive and negative charges a proach each other, the air becomes a good conductor of electricity.

Thus the electrons from the negatively charged cloud push their way through air so as to reach to the positively charged cloud. In doing so air gets white hot and hence a dazzling bluish white hot and hence a dazzling bluish white streak of light is formed, which is called lightning. Because of this intense heat produced, the air suddenly expands and sends out huge pressure waves. These waves produced thunder.

Question 4.
How does lightning takes place between the clouds?
Answer:
Normally air is a bad conductor of electricity. However when few clouds having huge amount of positive and negative static charges approach each other, the air becomes a good conductor of electricity.

Thus the electrons from the negatively charged cloud push their way through air. So as to reach to the positively charged cloud. In doing so the air gets white hot and hence a dazzling bluish white streak of light is formed which is called lightning. Because of this intence heat produced, the air suddenly expands and sends out huge pressure causes. These waves produce thunder.

Winds, Storms and Cyclones Class 7 HBSE Notes

1. Air around us exerts pressure.
2. Air expands on heating and contracts on cooling.
3. Warm air rises up, whereas comparatively cooler air tends to sink towards the earth’s surface.
4. As warm air rises, air pressure at that place is reduced and the cooler air moves to that place.
5. The moving air is called wind.
6. Uneven heating on the earth is the main cause of wind movements.
7. Winds carrying water vapour bring rain.
8. Thunderstorms develop in hot, humid tropical areas like India very frequently. The rising temperatures produce strong upward rising winds. These winds carry water droplets upwards, where they freeze, and fall down again.
9. The swift movement of the falling water droplets alongwith the rising air create lightning and sound. It is this event that we call a thunderstorm.
10. A cyclone is a storm in which the wind blows at a speed of about 300 km per hour. Cyclones develop over oceans but never close to the equator. They never originate from the land mass but may penetrate the margins of continents.
11. A cyclone is known by different names in different parts of the world. It is called a ‘hurricane’ in the
12. American continent. In Philippines and Japan its called a ‘typhoon’ and in Australia its called ‘willywillies’.
13. It has become easier to monitor cyclones with the help of advance technology like satellites and radars.
14. Self-help is the best help. Therefore, it is better to plan in advance and be ready with defence against any approaching cyclone.

Haryana State Board HBSE 7th Class Science Solutions Chapter 7 Weather, Climate and Adaptations of Animals to Climate Textbook Exercise Questions and Answers.

Haryana Board 7th Class Science Solutions Chapter 7 Weather, Climate and Adaptations of Animals to Climate

HBSE 7th Class Science Weather, Climate and Adaptations of Animals to Climate Textbook Questions and Answers

Question 1.
Name the elements that determine the weather of a place.
Answer:
The temperature, humidity, rainfall, wind-seed, etc. are called the elements of the weather, that determine the weather of a place.

Question 2.
When are the maximum and minimum temperature likely to occur during the day?
Answer:
The maximum temperature of the day occurs generally in the afternoon while the minimum temperature occurs generally in the early morning.

Question 3.
Fill in the blanks:
(i) The average weather taken over a long time is called ………… .
(ii) A place receives very little rainfall and the temperature is high throughout the year, the climate of that place will be………….. and ………….. .
(iii) The two regions of the earth extreme climatic conditions are …………… and ……………. .
Answer:
(i) the climate of the place
(ii) hot, dry
(iii) polar, tropical

Question 4.
Indicate the type of climate of the following areas:
(a) Jammu and Kashmir
(b) Kerla
(c) Rajasthan
(d) North-East India.
Answer:
(a) Jammu and Kashmir – moderately hot and moderately wet climate
(b) Kerala – very hot and wet climate
(c) Rajasthan – hot and dry climate
(d) North-east India – The north eastern India receives rain for a major part of the year. Therefore, we can say that the climate of the north-east is wet.

Question 5.
Which of the two changes frequently, weather or climate?
Answer:
Weather.

Question 6.
Following are some of the characteristics of animals:
(i) Diets heavy on fruits
(ii) White fur
(iii) Need to migrate
(iv) Loud Voice
(v) Sticky pads on feet
(vi) Layer of fat under skin
(vii) Wide and large paws
(viii) Bright colours
(ix) Strong tails
(x) Long and large beak
For each characteristic indicate whether it is adaptation for tropical rainforests or polar regions. Do yQU think that some of these characteristics can be adaptations for both the regions?
Answer:
(i) Diets heavy on fruits – tropical rainforests
(ii) White fur – polar regions
(iii) Need to migrate – pblar regions
(iv) Loud Voice – tropical rainforests
(v) Sticky pads, on feet – tropical rainforests
(vi) Layer of fat under skin – polar regions
(vii) Wide and large paws – polar Regions
(viii) Bright colours – tropical rainforests
(ix) Strong tails – tropical regions
(x) Long and large beak – tropical rainforests.

Question 7.
The tropical rainforests has a large population of animals. Explain why it is so?
Answer:
The tropical region has generally a hot climate because of its location around the equator. Even in the coldest month the temperature is generally higher than about 15°C. During hot summers, the temperature may cross 40°C. Days and nights are almost equal in length throughout the year. These regions get plenty of rainfall.

An important feature of this region is the tropical rainforests. Tropical rainforests are found in Western Ghats and Assam in India, South East Asia, Central America and Central Africa. Because of continuous warmth and rain, this region support wide variety of plants and animals. The major types of animals living in the rainforests are monkeys, apes, gorillas, lions, tigers,, elephants, leopards, lizards, snakes, birds and insects.

Question 8.
Explain, jirith examples, why we find animals of certain kind living in particular climatic conditions?
Answer:
Animals are adapted to survive in the conditions in which they live. Animals living in very cold and hot climate must possess special features to protect themselves against the extreme cold or heat.

Penguins are found in cold regions. They have a feathery coat as well as a layer of fat under the feathery coat. The coat covers their bodies right down to their legs. These adaptations keep the body warm.

Polar bear Eire found in the Arctic region where it is very cold. They have a thick layer of fur Emd a lot of fat in their bodies to keep them warm. Their soles are covered with fur to keep them warm. The white fur also helps the polar bears to blend with the snowy surroundings so that they are detected by the prey.!

Question 9.
How do elephant living in the tropical! rainforest adapt itself
Answer:
It has adapted to the conditions of rainforests in many remarkable ways. Trunks uses it as a nose because of which it has a strong sense of smell. The trunk is also used by it for picking up food. Moreover, its tusks are modified teeth. These can tear the bark of trees that elephant loves to eat. So, the elephant is able to handle the competition for food rather well. Large ears of the elephant help it to hear even very soft sounds. They also help the elephant to keep cool in the hot and humid climate of the rainforest.

Choose the correct option which answers the following questions (Question 10-12).

Question 10.
A carnivore with stripes on its body moves very fast while catching its prey. It is likely to be found in:
(i) polar regions
(ii) deserts
(iii) oceans
(iv) tropical rainforests
Answer:
(iv) tropical rainforests

Question 11.
Which features adapt polar bears to live in extremely cold climate?
(i) A white fur, fat below skin, keen sense of smell.
(ii) Thin skin, large eyes, a white fur.
(iii) A long tail, strong claws, white large paws.
(iv) White ‘body, paws for swimming, gills for respiration.
Answer:
(i) A white fur, fat below skin, keen sense of smell.

Question 12.
Which option best describes a tropical region?
(i) hot and humid
(ii) moderate temperature, heavy rainfall
(iii) cold and humid
(iv) hot and dry
Answer:
(i) hot and humid

Extended Learning – Projects And Activities

Question 1.
Collect weather reports of seven successive days in the winter months (Preferably December). Collect similar reports for the summer months (Preferably June). Now prepare a Table for sunrise and sunset times as shown:

Try to answer the following questions:

• Is there any difference in the time of sunrise during summer and winter?
• When do you find that the sun rises earlier?
• Do you also find any difference in the time of sunset during the month of June and December?
• When are the days longer?
• When are the nights longer?
• Why are the days sometimes longer and sometimes shorter?
• Plot the length of the day against the days chosen in June and December. (Instructions for plotting graphs are given in Chapter 13).
  Answer:
  Do yourself.

Question 2.
Collect information about the Indian Meteorological Department. If possible visit its website: htt/www.imd.gov.in.
Write a brief report about the things this department does.
Answer:
Do yourself.

HBSE 7th Class Science Weather, Climate and Adaptations of Animals to Climate Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is raingauge?
Answer:
Rainfall is measured by an instrument called the rainguage. It is basically a measuring cylinder with a funnel on top to collect rainwater.

Question 2.
Define weather.
Answer:
The day-to-day condition of the atmosphere at,’a place with respect to the temperature, humidity, rainfall, wind speed, etc., is called the weather of that place.

Question 3.
Who prepares the weather reports?
Answer:
The weather reports are prepared by the Materological Department of the Government. This department collects data on temperature, wind etc., and makes the weather prediction.

Question 4.
Define climate.
Answer:
The average weather pattern taken over a long time, say 25 years, is called the climate of the place.

Question 5.
Why do some places have hotter climate than others?
Answer:
The places nearer to the equator are usually hotter. This is because the sun’s rays are more concentrated near the equator than they are farther North or South.

Question 6.
Give two examples of animals found in cold climates.
Answer:
(i) Penguins
(ii) Polar bear.

Question 7.
Give two examples of animals found in hot and humid climate.
Answer:
(i) Red-eyed frog
(ii) Beard ape.

Question 8.
Name three desert animals.
Answer:
(i) Camel
(ii) Snake
(iii) Lizard.

Question 9.
Can a polar bear live happily on land?
Answer:
No, it lives where the land is fully covered with snow.

Question 10.
Where do the elephant live?
Answer:
Elephant lives in forest.

Question 11.
Where does penguin live?
Answer:
Penguin lives in very cold places.

Question 12.
Define adaptation.
Answer:
The particular features of an organism that makes it suited to a particular climate is called adaptation.

Question 13.
What do you understand by ‘summer sleep’?
Answer:
Animals like frog, crocodiles and alligators live in mud during the summer months. This is called the ‘summer sleep’.

Question 14.
What do you understand by hibernation?
Answer:
During winter, some animals like bears, bats, snakes, lizards, frogs and squirrels go to sleep. This is called the winter sleep or hibernation.

Question 15.
Where do the following animals live?
(i) Monkeys
(ii) Snakes
(iii) Rabbit
(iv) Fish.
Answer:
(i) On land and trees
(ii) On land and water
(iii) On land
(iv) In water.

Question 16.
Name three animals which are active during night;
Answer:
(i) Bat
(ii) Owl
(iii) Cockroach.

Question 17.
What is the difference between climate of Kashmir and Kerala?
Answer:
Kerala is very hot and wet in comparison to Kashmir, which has a moderately hot and moderately wet.

Question 18.
Name two countries where polar regions are found?
Answer:
(i) Canada
(ii) Sweden.

Question 19.
Name two countries where the tropical rainforests are found?
Answer:
(i) India
(ii) Malaysia.

Question 20.
Name a migratory bird.
Answer:
Siberian crane.

Short Answer Type Questions

Question 1.
Why do desert animals have thick skin?
Answer:
Animals living in hot places, such as snakes, desert rats and lizards are not able to get sufficient water. So these animals have a thick skin, which prevents evaporation. Since they do not sweat, they can survive| without water for a longer time.

Question 2.
How is camel adapted live in/ desert?
Answer:
Camel lives in desert. It has long legs which help it to lift its body above the ground. Thus camel is able to avoid direct contact with the hot ground. The camel drinks water 50 litre or above in one time and store it in its body. So it lives without water for longer time. Its skin is also thick which prevents transpiration of ‘ water. Thus camel is suited to live in desert.

Question 3.
How cold place animals protect themselves from cold?
Answer:
The animals which live in cold places like waives seals, and penguins have thick skin which protects them from cold. They also have thick ,fur.

Question 4.
How fishes are adapted to live in water?
Answer:
Fishes are best suited to live in water. They have boat like structure which help them in swimming in water. They have gills from which they get oxygen and food. The body of fishes contain different types of fins which help them from swimming in water. Fishes shape tapers which provide least resistance in swimming water.

Question 5.
Why do polar bears have white fur?
Answer:
Polars bears have white fur so that they are not easily visible in the snowy white background. It protects them from their predators. It also helps them in catching their prey. To protect them from extreme cold, they have two this layers of fur. They also live a er of fair under their skin.

Question 6.
Differentiate between weather and climate.
Answer:

Question 7.
Give some examples of sea water animals.
Answer:
Almost all types of animals live in sea water. Most of the sea water animals are actively swimming animals like fishes and whales. Animals like corals, star fish, and urchin live at the bottom of the sea.s

Question 8.
Write the factors which the climate of a region depend.
Answer:
The climate of a region depends on:
(i) The presence or absence of water (rainfall).
(ii) Amount of sunshine it gets.
(iii) The ability to transfer water to the atmosphere (evaporation), and
(iv) The place whether it is a hilly or a plain region.

Question 9.
Mention the adaptive features of the animals found n cold climates.
Answer:
The animals found in cold climates have a thick layer of fat under the skin. This gives them nourishment in winter. They also have thick coat of fur on their body which helps the stay warm. The examples of animals 6 in cold regions are reindeer, arctic fox, polar bear, etc.

Question 10.
Mention the adaptations in hot and dry climates.
Answer:
Animals living in hot and dry places usually have following adaptations:
(i) Short shiny fur to reflect the sun’s rays.
(ii) Keep the body cool through sweating and panting.
(iii) To avoid the strong sun, they feed in the morning or evening and hide behind rocks and in burrows during the day.
Examples: Camel, Ostrich and Snail.

Long Answer Type Questions

Question 1.
The Earth is the only planet on which life is exists, why? Explain.
Answer:
The Earth is not the only planet revolving around the Sun. There are eight other planets that revolve Ground tfye Sun. But Earth is the only planet on which life exists. A number of factors are responsible for it. These are:
(i) Distance of Earth from the Sun; this is sufficient to keep the temperature’ on the surface of Earth at an average of 30°C; life can exist at this temperature.
(ii) The layer of carboh dioxide and watervapour which surrounds Earth prevents too much heat from leaving Earth into space; otherwise the temperature of Earth would be -30°C.
(iii) The layer of Zone which surrounds Earth does not allow ultraviolet rays to reach Earth from the sun, other wise living onganisns will die.

Question 2.
Describe the adaptive features of camel.
Answer:
The camel is the animal that thrives on the best in such hpt climate. It is also called the ship of the desert. The camel is called so because of the following adaptations it has:
(i) Thick skin that prevents water loss through perspiration or evaporation.
(ii) Humps (one or two) present in the body. These are the storehouse of fat. The camel uses this fat when food is scarce.
(iii) Pouches in the body to store water. This enables the camei to go without water for many days.
(iv) Pads of skin under the feet that act like cushions and enable the camel to walk easily in the sand without sinking.
(v) Long curly eyelashes preventing the entry of sand into eyes and thick eyebrows to protect eyes from sun. The plants and animals living in cold regions also have certain features. These are different from those possessed by plants and animals living in hot regions.

Question 3.
Defind adaptation. Mention various adaptations in terrestrial animals.
Answer:
Climate influences living organisms directly. Hence, they develop certain traits that help them to thrive well in that particular climate. This is called adaptation.

The animals that live on land are called terrestrial animals. These animals have different types of habits and ways of living. The terrestrial animals may be runners (cursorial habit), burrowers and diggers (fossorial habit), climbers (scansorial or arboreal habit) and fliers (aerial habit). Accordingly, these animals have different types of adaptations, as described below.
A. Modification of foot: Terrestrial animals have different types of foot for locomotion.
(i) Pentadactily: Terrestial animals have pentadactyl (five digits) foo; bearing claws for walking and running. Pentadactyl foot are of following three types:
(а) Plantigrade: In this type of foot, the entire palm and sole rest on the ground e.g. bear, baboon, raccoon.
(b) Digitigrade: In this case, animals perform walking and running on the digits e.g. dogs, cat, hyaena.
(c) Unguligrade: In this case, animals perform walking and running on the tips of digits covered with modified nail called hoof. The distal toe bones (unguals) are depressed or flattened, e.g. pig, horse, donkey, rhinoceros.

(ii) Bipedality: Some terrestrial animals have two footed or bipedal mode of locomotion, which spares forelimbs for other types of jobs. e.g. human beings.

B. Modification of body and head:
(i) The fast moving animals like horse, dog, etc. have streamlined body to reduce the resistance offered by the air.
(ii) In burrowing and digging animals, the head and snout are tapering. e.g. snakes, shrew, mole.

C. Modification for respiration:
The majority of terrestrial animals are lung breathers. They have lungs for respiration, e.g. Frog, lizards, all mammals.

D. Protective adaptations:
Many terrestrial animals are able to modify their form, appearance, structure or behaviour to escape predation or to increase the chances of capturing the prey. For example frog can change its body colour to match the back ground.

Question 4.
Mention various adaptations in aquatic animals.
Answer:
A large number of animals live in aquatic habitat. They include both fresh water and marine (sea water) forms. Several invt ibrates such as prawn, Octopus, some insects are aquatic or semi aquatic. A number of vertebrates such as fishes, whales, dolphins are well adapted to aquatic mode of life. They have following adaptation for aquatic mode of life.
(i) Body contour: They have streamlined laterally compressed body to reduce friction. This allows swift passage in water while swimming.
(ii) Swimming organs: The fishes have fins and whales possess flippers which help them in swimming. Frogs and ducks have webbed feet for swimming.
(iii) Protective covering: The body of fishes is covered with scales and that of frog with a mucilaginous covering, which protect them from decaying effect of water.
(iv) Gills: Fishes have special breathing organs called gills, which use dissolved oxygen of water.
(v) Swim bladder or Air bladder:
Certain fishes (bony fishes) have swim bladder or air bladder. It is filled with air and maintain buoyancy.

Weather, Climate and Adaptations of Animals to Climate Class 7  HBSE Notes

1. The day-to-day condition of the atmosphere at a place with respect to the temperature, humidity, rainfall, wind-speed, etc.; is called the weather at that place.
2. The temperature, humidity and other factors are called the elements of the weather. The weather of a place charges day after day and week after week.
3. The maximum temperature of the day occurs generally in the afternoon while the minimum temperature occurs in the early morning.
4. The times of sunrise and sunset also change during the year.
5. All the changes in the weather are driven by the sun.
6. The average weather pattern taken over a long time, say 25 years, is called the climate of the place.
7. The tropical and the polar regions are the two regions of the earth, which have severe climate conditions. .
8. Animals are adapted to the conditions in which they live.
9. The polar regions are very cold throughout the year. The sun does not set for six months in a year and in the other six months it does not rise.
10. Animals in the polar region are adapted to the extremely cold climate by having some special characteristics such as white fur, strong sense of smell, a layer of fat under the skin, wide and large paws for swimming and walking etc.
11. Migration is another means to escape the harsh, cold conditions.
12. Because of the hospitable climatic conditions, huge populations of plants and animals are found in the tropical rainforests.
13. Animals in the tropical rainforests are adapted such that they eat different kinds of food to overcome the competition for food and shelter.
14. Some adaptations of animals living in the tropical rainforests include living on the trees, development of strong tails, long and large beaks, bright colours, sharp patterns, loud voice, diet of fruits, sensitive hearing, sharp eyesight, thick skin, ability to camouflage in order to protect themselves from predators etc.

Haryana State Board HBSE 7th Class Science Solutions Chapter 6 Physical and Chemical Changes Textbook Exercise Questions and Answers.

Haryana Board 7th Class Science Solutions Chapter 6 Physical and Chemical Changes

HBSE 7th Class Science Physical and Chemical Changes Textbook Questions and Answers

Question 1.
Classify the changes involved in the following processes as physical or chemical changes.
(a) Photosynthesis
(b) Dissolving sugar in water
(c) Burning of coal
(d) Melting of wax
(e) Beating aluminium to make aluminium foil
(f) Digestion of food.
Answer:
Physical Change (b), (d), (e)
Chemical Change (a), (c), (f)

Question 2.
State whether the following statements are true or false. In case a statement is false, write the corrected statement in your notebook.
(a) Cutting a log of wood into pieces is a chemical change.
(b) Formation of manure from leaves is a physical change.
(c) Iron pipes coated with zinc do not get rusted easily.
(d) Iron and rust are the same substances.
(e) Condensation of steam is not a chemical change.
Answer:
(a) False
(b) False
(c) True
(d) True
(e) True.

Question 3.
Fill the blanks in the following statements:
(a) When carbon dioxide is passed through lime water, it turns milky due to the formation of ………….. .
(b) The chemical name of baking soda is ……………… .
(c) Two methods by which rusting of iron can be prevented are …………. and …………. .
(d) Changes in which only …………. properties of a substance change are called physical changes.
(e) Changes in which new substances are formed are called …………. changes.
Answer:
(a) Calcium carbonate
(b) Sodium hydrogen carbonate
(c) Coating, galvanization
(d) Physical
(e) Chemical.

Question 4.
When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.
Answer:
When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas carbon dioxide.
lemon juice + baking soda → carbon dioxide + lime water
Since, a change in which one or more new substance are formed is called a chemical change, therefore this is a chemical change.

Question 5.
When a caùdie burns, both physical and chemical changes take place. Identify these changes. Give another example of a familiar process in which both the chemical and physical changes take place.
Answer:
Physical Change → Melting of ware
Chemical Change → Burning of candle

Question 6.
How would you show that setting of curd is a chemical change?
Answer:
The conversion of milk into curd, i.e., setting of curd is a permanent as well as irreversible and lead to the production of a new substance. The new substance, curd is formed has different composition and properties from the milk. Hence, setting of curd is a chemical change.

Question 7.
Explain why burning of wood is cutting it into small pieces are considered as two different types of a changes.
Answer:
Burning of wood is a chemical change because, in addition to new products burning is always accompanied by production of heat.
Cutting of wood into small pieces is a physical change because, pieces of wood underwent changes in size and no new substance is formed.

Question 8.
Describe how crystals of copper sulphate are prepared.
Answer:
Take a cup full of water in a beaker and add a few drops of dilute sulphuric acid. Heat the water. When it starts boiling add copper sulphate powder slowly while stirring continuously. Continue adding copper sulphate powder till no more powder can be dissolved. Filter the solution. Allow it to cool. Do not disturb the solution when it is cooling. Look at the solution after some time. Now, you can see the crystals of copper sulphate.

Question 9.
Explain how painting of an iron gate prevents it from rusting.
Answer:
The process of rusting can be represented by the following equation:
Iron (Fe) + Oxygen (O₂ from the air) + Water (H₂O) → rust (iron oxide Fe₂O₃).

For rusting the presence of both oxygen and water (or water vapour) is essential. In fact, if the content of moisture in air is high, which means if it is more humid, rusting becomes faster. So, prevent iron gate from coming in contact with oxygen, or water, or both. One simple way is to apply a coat of paint or grease. In fact, these coats should be applied regularly to prevent rusting.

Question 10.
Explain why rusting of iron objects is faster in coastal areas than in deserts.
Answer:
The water of coastal areas contain many salts. The salt water makes the process of rust formation faster. Thus, rusting of iron objects is faster in coastal areas than deserts.

Question 11.
The gas we use in the kitchen is called liquified petroleum gas (LPG). In the cylinder it exist as a liquid. When it comes out from the cylinder it becomes a gas (Change – A) then it burns (Change – B). The following statements pertain to these changes. Choose the correct one.
(i) Process – A is a chemical change
(ii) Process – B is a chemical change.
(iii) Both processes A and B are chemical changes.
(iv) None of these processes is a chemical change.
Answer:
(iii) Both process A and B are chemical changes.

Question 12.
Anaerobic bacteria digest animal waste and produce biogas (Change – A). The biogas is then burnt as fuel (Change – B). The following statements pertain to these changes. Choose the correct one.
(i) Process – A is a chemical change,
(ii) Process – B is a chemical change.
(iii) Both process A and B are chemical changes.
(iv) None of these processes is a chemical change.
Answer:
(iii) Both process A and B are chemical changes.

Extended Learning – Activities And Projects

Question 1.
Take three glass bottles with wide mouths. Label them A, B and C. Fill about half of bottle A with ordinary tap water. Fill bottle B with water which has been boiled for several minutes, to the same level as in A. In bottle C, take the same boiled water and of the same amount as in other bottles. In each bottle put a few similar iron nails so that they are completely under water. Add a teaspoonful of cooking oil of the water in bottle C so that it forms a film on its surface. Put the bottles away for a few days. Take out nails from each bottle and observe them. Explain your observations.
Answer:
Do yourself.

Question 2.
Prepare crystals of alum.
Answer:
Do yourself.

Question 3.
Collect information about the types of fuels used for cooking in your area. Discuss with your teachers/parents/others which fuels are less polluting and why.
Answer:
Do yourself.

HBSE 7th Class Science Physical and Chemical Changes Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is a physical change?
Answer:
Change in which no new product is formed.

Question 2.
What is a chemical change?
Answer:
A change in which a new substance with different properties is formed.

Question 3.
Which of the following substance contains only one kind of atoms?
copper, iron, iron sulphide, sulphur, oxygen gas, water, air and hydrogen gas.
Answer:
The following contains only one kind of atoms:
Copper, Iron, Sulphur, Oxygen gas, Hydrogen gas.

Question 4.
Which of the following substances are compounds and which are elements?
Magnesium oxide, Mercuric oxide, Carbon, Nitrogen, Potassium permagnate, Sodium carbonate.
Answer:
Elements: Carbon, nitrogen.
Compounds: Magnesium oxide, mercuric oxide, potassium permanganate, Sodium carbonate.

Question 5.
Write the symbol of the following elements:
Aluminium, calcium, chlorine, cobalt, iodine and mercury.
Answer:
Al, Ca, Cl, Co, I, Hg.

Question 6.
Ne is the symbol of neon. What else does it represent?
Answer:
This symbol represent one atom of Neon.

Question 7.
Which elements are represented by the following symbols?
Na, K, P, Pb, Ca, Zn, Br, Sn.
Answer:
Sodium, Potassium, Phosphorus, Calcium, Zinc, Bromine, Tin.

Question 8.
Name four Elements which occur in gaseous form.
Answer:
Oxygen, Nitrogen, Hydrogen and Argon.

Question 9.
When some one open a bottle of perfumes, you smell it from a distance why it is so?
Answer:
It is due to the property of gases that their molecules diffuse (move) easily in the air.

Question 10.
What is crystallisation?
Answer:
The process of separation of pure crystals of a substance from its hot and supersaturated (concentrated) solution on cooling is called
crystallisation.

Question 11.
Define chemical reaction.
Answer:
The process in which the originally present substances change into new substances is called a chemical reaction.

Question 12.
What is matter?
Answer:
Anything which occupies space and has weight is called matter. Example: Air, Water, Wood, Stone, etc.

Question 13.
What are solids?
Answer:
Any materials which has a definite shape and definite volume, at room temperature is called solid.

Question 14.
What are liquids?
Answer:
Any substance which has a definite volume but no definite shape and has one free surface is called liquids: Milk, Water, Fruit juice, Alcohol etc.

Question 15.
Name two elements that are abundantly found in air.
Answer:
The two elements that are found abundantly in air are Nitrogen element and Oxygen element.

Question 16.
Choose the elements from the following substances: Marble, Mercury, Air, Carbon.
Answer:
Mercury and Carbon are elements.

Question 17.
What is the difference between 2N and N?
Answer:
2N represent 2 atoms of nitrogen and N represent 1 molecule of nitrogen.

Question 18.
Which of the following contains only one kind of atoms?
Copper, Iron sulphide, Sulphur, Oxygen gas, Water, Air and Hydrogen gas.
Answer:
Copper, Iron, Sulphur, Oxygen gas, Hydrogen gas.

Question 19.
Which of the following substances are compounds and which are elements?
Magnesium oxide, nitrogen, potassium permanganate, sodium carbonate.
Answer:
Compounds: Magnesium oxide, Potassium permanganate, Sodium carbonate.
Elements: Nitrogen.

Question 20.
Write down the chemical symbols of the following elements: Potassium, Calcium, Phosphorus, Nitrogen, Sulphur.
Answer:
K, Ca, P₄, N and Sg.

Question 21.
Write the names of the elements having the following symbols: C, Br, P, Al, Si.
Answer:
Carbon, Bromine, Phosphorus, Aluminium and Silicon.

Question 22.
A given substance ‘X’ has definite shape, fixed volume, is in comprissible and non-diffusing. What is the physical state of the substance ‘X’?
Answer:
The substance ‘X’ is solid state.

Question 23.
Write the names of the elements which compose a molecule of water.
Answer:
Hydrogen and Oxygen.

Question 24.
Name the three most abundant elements on the earth’s crust.
Answer:
Iron, Aluminium and Silicon.

Question 25.
Give the chemical formulae of the following:
(i) Calcium hydroxide
(ii) Copper oxide
(iii) Iron chloride
(iv) Zinc nitrate
(v) Silver sulphate
(vi) Lead carbonate
(vii) Potassium phosphate
(viii) Sodium hydroxide
(ix) Hydrochloric acid
(x) Zince hydroxide.
Answer:
(i) Ca(OH)₂
(ii) CuO
(iii) FeCl₂
(iv) Zn (NO₃)₂
(v) Ag₂SO₄
(vi) PbCO₃
(vii) K₃PO₄
(viii) NaOH
(ix) HCl
(x) Zn(OH)₂.

Question 26.
Define reactents.
Answer:
The original substances that take part in a chemical reaction are called the reactants,

Question 27.
Define products.
Answer:
The substances that form as a result of chemical reaction are called the products.

Question 28.
Define chemical combination reaction.
Answer:
When two or more elements or compounds react chemically to form only one new product, then the reaction which takes place is called chemical combination.

Question 30.
Define chemical displacement reaction.
Answer:
When a more reactive element displaces a less reactive elements from its aqueous salt solution, the reaction which takes place is called chemical displacement.

Question 31.
What kind of chemical reaction takes place when a mixture of iron fillings are heated with sulphur?
Answer:
Chemical combination reaction.

Short Answer Type Questions

Question 1.
Formation of clouds is a physical change. Explain.
Answer:
Formation of clouds is a physical change. Clouds are formed by condensation of water vapours present in the atmosphere. When rainwater goes back on the earth no new product is formed. Therefore, it is a physical change.

Question 2.
Explosion of a cracker is a chemical change. Explain.
Answer:
When we burn a cracker, it exploide. Heat, light and smoke comes out after explosion. Many new products are formed. So, it is a chemical change.

Question 3.
Most physical changes are reversible. Give reasons with two examples.
Answer:
All physical changes are reversible. Because in physical changes, no new product is formed. They can be reversed easily.
Examples:
(i) Dissolving of sugar in water is a physical change and we get back sugar and water easily.
(ii) Formation of ice from water. In melting of ice, we can get water back.

Question 4.
Identify the type of change and state whether energy is evolved or absorbed in each one of the following:
Burning of a candle, lighting of a bulb, preparation of food by green plants, Volcanic eruption.
Answer:
(i) Burning of a candle: Chemical change, energy evolved.
(ii) Lighting of a bulb: Physical change, energy evolved.
(iii) Preparation of food by green plants: Chemical change, energy absorbed.
(iv) Volcanic eruption: Chemical change, energy evolved.

Question 5.
What is a chemical formula? What information does it provide?
Answer:
Chemical formula is a shorthand method of using symbols to represent the composition of a compound. Using it, we can get the following informations:
(i) Constituting name of the elements present in the compound, e.g., water has the formula H₂0. It shows that water is made up .. of two elements, hydrogen and oxygen.
(ii) Atoms present in each element, e.g.,
(iii) The composition of compound and the formula H₂O shows that in a molecule of molecular weight of the compound, this compound two atoms of hydrogen and one atom of oxygen are present.

Question 6.
What are the differences between chemical and physical changes?
Answer:
Differences between chemical and physical changes:

Question 7.
How is common salt obtained from sea water?
Answer:
In the coastal regions of India, especially in the Rann of Kutch in Gujarat and some parts of Tamil Nadu, the sea water is collected in shallow pits. It is then allowed to evaporate in the sun. As the water evaporates, the salt solution becomes supersaturated. This supersaturated solution cannot hold the excess salt. Thus, it separates out in form of salt crystals. These salt crystals are collected. They are redissolved in water and the solution is filtered to remove insoluble impurities. The clear solution is again evaporated so as to obtain the crystals of pure salt.

Question 8.
What is crystallisation? To what purpose is it put?
Answer:
The process of separation of pure crystals of a substance from its hot and supersaturated (concentrated) solution on cooling is called Crystallisation.

The process of crystallisation is employed for the separation of a pure water soluble substance from its mixture. For example, if there is a mixture of alum and common salt, the pure alum crystals can be separated by the process of crystallisation.

Question 9.
What is the significance of an equation?
Answer:
Significance of an equation:
(i) It tells us which substance reacted and which substances are produced.
(ii) It tells us the quantities of each of the reactants and each of the products.

Question 10.
Give four examples of a physical change.
Answer:
(i) Formation of dew.
(ii) Evaporation of water.
(iii) Melting of wax.
(iv) Making of ice-cream.

Question 11.
Give four examples of a chemical change.
Answer:
(i) Photosynthesis by plants.
(ii) Clotting of blood.
(iii) Curdling of milk.
(iv) Burning of candle.

Question 12.
State four characteristics of physical change.
Answer:
(i) It is temporary.
(ii) It is reversible.
(iii) No new substance is produced.
(iv) No change in the chemical properties.

Question 13.
State four characteristics of chemical change.
Answer:
(i) It is permanent.
(ii) It is irreversible.
(iii) New substance is produced.
(iv) Changes in the chemical properties due to the formation of new substances.

Question 14.
What happens when an iron blade of a knife is dipped in copper sulphate solution? What kind of chemical reaction takes place?
Answer:
When an iron blade of a knife is dipped in copper sulphate solution iron blade is coated with reddish deposit of copper. Thus, we can say that iron (more reactive element), displaces copper (less reactive element), from its aqueous copper sulphate solution. Chemical displacement reaction is takes place.

Question 15.
Why do the molecules in a liquid tend to stay together and give a condensed form?
Answer:
In a liquid, the molecular motion are not great enough to over come the force of attraction between molecules. That is why the molecules tend to stay together and give a condensed form.

Question 16.
On a hot summer day the cycle tubes burst suddenly. Explain why?
Answer:
The cycle tubes are filled with air. On a hot summer day, the temperature of the atmosphere is high. When cycle runs on the road, the friction between the cycle wheel and the path produces heat which raises the temperature of the air in the cycle tubes. On heating the air expands and exerts pressure in the inside of the tubes. Due to the pressure, the cycle burst suddenly on a hot summer day.

Question 17.
Why can the same substance exist in all the three states, that is, solid liquid and gas?
Answer:
The space between the molecules, the force of attraction between the molecules, and the amount of movement of the molecules of a substance can be changed by changing the pressure and temperature of the substance. So depending on the pressure and temperature, the same substance can exist in all the three states i.e., Solid, liquid and gaseous. For example under normal pressure water exists as a solid in the form of ice at a temperature of 0°C or below. It exists as a liquid in the form of water at the room temperature and as a gas in the form of steam at 100°C or above.

Question 18.
Write some important properties of an element.
Answer:
Properties of an element are:
(i) An element is made up of some kinds of atoms.
(ii) An element cannot be Broken up into much simpler substances,
(iii) An element can be represented by a chemical symbol.

Question 19.
What are the important characteristics of a compound?
Answer:
(i) Chemical compound is made up of two or more elements combined chemically.
(ii) They have fixed formula or composition.
(iii) They have fixed melting point (M.P.) and boiling point (B.P.).
(iv) Energy is either evolved or absorbed during formation of a compound.
(v) Properties of constituent elements are different from its compound, e.g., properties of water (H₂O) are different from properties of hydrogen and oxygen.

Question 20.
What does the formula CO₂ represent?
Answer:
Molecular formula CO₂ represents:
(i) the name of the compound carbon dioxide.
(ii) carbon dioxide is made up of two kinds of elements – carbon and oxygen.
(iii) one molecule of carbon dioxide has one atom of carbon and 2 atoms of oxygen.
(iv) the molecular mass of carbon dioxide is 12 + 2 x 16 = 44 gram.

Question 21.
How is salt obtained from sea-water?
Answer:
The seas are great sources of salts. A litre of a water contains about 35 grams of salts. Sodium chloride is the main salt. The sea-water is trapped in shallow called lagoons and is allowed to evaporate in sunlight to white solid crystal of salts. These crystals are processed and packed to send the markets.

Question 22.
Give three reasons for supporting that water is a compound and not a mixture.
Answer:
Water is considered a compound due to the following reasons:
(i) Water cannot be separated into its constituents, hydrogen and oxygen, by the physical process.
(ii) The properties of water are entirely different from those of its constituents hydrogen and oxygen.
(iii) Water contains hydrogen and oxygen combined together in a fixed proportions of 1:8 by weight.

Question 23.
Explain why solution of salt in water is considered a mixture and not a compound. Give three reasons.
Answer:
Salt solution is considered a mixture due to the following reasons:
(i) Salt solution can be separated into salt and water by the physical process.
(ii) Salt solution, shows the properties of both its constituents salt as well as water.
(iii) The composition of salt solution is variable i.e., the percentage of salt and water in different salt solutions are different.

Question 24.
What information do we get from a chemical equation?
Answer:
The informations obtained from a chemical equation are:
(i) Name of the substance (elements or compound) taking part in reaction, i.e., reactants and products.
(ii) The number of atoms and molecules of different substances.
(iii) The conditions under which the reaction takes place or taking part in reaction, for example:
N₂ + 3H₂ → 2NH₃
It represents 1 molecule of nitrogen combines with 3 molecules of hydrogen to form 2 molecules of ammonia.

Question 25.
“In a chemical reaction, there is only a rearrangement of the atoms of the reactants.” Explain this statement giving an example.
Answer:
In a chemical reaction, there is only a x’e. angement of the atoms of the reactants because when a chemical reaction occurs new products are formed. These products have same kind and number of atoms as are present in reactants. They are only rearrange to give new substances. For example, in a reaction between iron and sulphur to give iron sulphide the number of atoms of iron and sulphur are identical on both sides of the equation.
Fe + S → FeS (On heating)

Question 26.
What is done to make a chemical equation more informative?
Answer:
To make a chemical equation more informative it should be balanced and conditions of the reaction should be written above the arrow. For example,

It shows that 2 molecules of water on electrolysis break up into 2 molecules of hydrogen and 1 molecule of oxygen.

Question 27.
What do you understand by reactants and products?
Answer:
Reactants: Substances taking part in a reaction are called reactants. They are written on the left side of the chemical equation.
Products: Substances produced in a reaction are called products. They are written on the right side of the equation.
Example:

Long Answer Type Questions

Question 1.
What does a chemical formula represent?
Answer:
Significance of chemical formula:
(i) It represents the name of the substance.
(ii) It represents one molecule of the substance.
(iii) It gives the names of all the elements present in the molecule.
(iv) It represents the mass of one molecule.

As an example of the formula of H₂SO₄:
(i) Represents sulphuric acid.
(ii) Represent one molecule of sulphuric acid.
(iii) Tells that sulphuric acid contains three elements:
hydrogen, sulphur, and oxygen.
(iv) Tells that one molecule of sulphuric acid contains two atoms of hydrogen; 1 atom of sulphur and 4 atoms of oxygen.

Question 2.
What do you understand by the following terms? Give examples.
(i) Endothermic chemical change
(ii) Exothermic chemical change.
Answer:
(i) Endothermic chemical change: When a chemical change takes place with the absorption of heat energy, then the change is said to be endothermic. .
Examples: Heating of mercuric oxide to form mercury and oxygen. Heating of calcium carbonate to form calcium oxide and carbon dioxide.

(ii) Exothermic chemical change: When a chemical change takes place with the liberation of heat energy, the change is said to be exothermic.
Examples: Candle on burning liberates heat and light energy. Respiration is an exothermic change.

Question 3.
What is a compound? How does it differ from a mixture?
Answer:
A compound consists of two or more elements, joined together in a fixed ratio by chemical bonds. For example, water formed from hydrogen and oxygen, sodium chloride formed from sodium and chlorine, sugar formed from carbon, hydrogen and oxygen, nitre formed from potassium, nitrogen and oxygen are all compound.
Difference between compounds and mixtures:

Question 4.
What is the difference between a balanced and unbalanced chemical equations? Explain with an example.
Answer:
Difference between a balanced and unbalanced chemical equations:
In unbalanced chemical equations, the number of each element atoms do not same. As for example:
Mg + O₂ → MgO.
This is not a balanced equation because the number of Mg atom and oxygen atoms are not same on both the sides, Le., reactants and product sides. On the other hand, in a balanced chemical equation the number of each atoms of each elements on both sides should be equal. As for example:
2Mg + O₂ → 2MgO.
In this balanced chemical equation the number of magnesium atoms and oxygen atoms in the left hand side are equal to the right hand side of the equation. So it is a balanced chemical equations.
(i) A mixture consists of two or more chemically different substances.
(ii) The composition of mixture can be separated easily by simple means.
(iii) Its formation is not accompanied by absorption or evolution of heat, light or electricity.
(iv) Mixture do not have definite formula.
(v) Mixture do not have fixed M.P. and B.P.
(vi) Mixture can be homogeneous and heterogenous.

Question 5.
Balance the following equations:
(i) Fe + O₂ → Fe₂O₃
(ii) H₂O + H₂ → O₂
(iii) Mg + O₂ → MgO
(iv) Al + O₂ → Al₂O₃
(v) Fe + HCl → FeCl₃ + H₂
(vi) Cu + O₂ → CuO
(vii) Hg + O₂ → HgO
(viii) Zn + HCl → ZnCl₂ + H₂
(xi) Al + HCl → AlCl₃ + H₂
(x) N₂ + H₂ → NH₃
Answer:
(i) 4Fe + 3O₂ → 2Fe₂O₃
(ii) 2H₂O → 2H₂ + O₂
(iii) 2Mg + O₂ → 2MgO
(iv) 4Al + 3O₂ → 2Al₂O₃
(v) 2Fe + 6HCl → 2FeCl₃ + 3H₂
(vi) 2Cu + O₂ → 2CuO
(vii) 2Hg + O₂ → 2HgO
(viii) Zn + 2HCl → ZnCl₂ + H₂
(xi) 2Al + 6HCl → 2AlCl₃ + 3H₂
(x) N₂ + 3H₂ → 2NH₃

Physical and Chemical Changes Class 7  HBSE Notes

1. Properties such as shape, size, colour and state of a substance are called its physical properties.
2. A change in which a substance undergoes a change in its physical properties is called a physical change. A physical change generally reversible.
3. A change in which one or more new substances are formed is called a chemical change. A chemical change is also called a chemical reaction.
Some common examples of chemical change:
1. Burning of wood or charcoal.
2. Burning of Candle.
3. Decomposition of water into hydrogen and oxygen.
4. Formation of water from hydrogen and oxygen.
5. Digestion of food.
6. Curdling of milk.
7. Formation of biogas (Crobar gas).
8. Burning of petrol or diesel.
9. Smoking of cigarette.
10. Drying of paint.
11. Rusting of iron.
12. Ripening of fruit.
13. Baking of cake.
14. Photosynthesis by plants.
15. Formation of wine.

Some Common Examples of Physical Changes:
1. Formation of dew.
2. Evaporation of water.
3. Crystallisation of sugar from its solution.
4. Ringing of an electric bell.
5. Breaking of glass pane.
6. Making of ice-cream.
7. A rock rolling down a hill.
8. Bending of glass tube by heating.
9. Melting of wax.
10. Sublimation of camphor.

4. If you leave a piece of iron in the open for some time, it acquires a film of brownish substance. This substance is called rust and the process is called rusting.
5. Any pure substance which cannot be broken into two or more pure substances by any chemical means is called an element.
6. The smallest unit of an element, which takes part in a chemical reaction is called an atom.
7. The smallest unit of a pure substance, which always exists independently and can retain physical and chemical properties of that substance, is called a molecule.
8. A metal is an element which is generally malleable, ductile and a good conductor of heat and electricity. About 80% of the elements are metals.
9. Non-metals are bad conductors of heat and electricity. They are neither malleable nor ductile. Non-rr Hals are generally soft.
10. When the molecule of a substance contains two or more atoms of different elements, combined together in a definite ratio, then it is said to be a molecule of a compound.
Symbols of common elements (Metals)

11. When one or more substances (elements or compounds) undergo a chemical change, with the absorption or release of energy, so as to form one or more new products, then the change taking place collectively is called chemical combination.
12. When two or more elements or compounds react chemically to form only one new product, then the reaction which takes place is called chemical combination.
13. When a single chemical compound decomposes on heating or by some other kind of energy, so as to form two or more new substances (elements or compounds), then the chemical reaction which takes place is called chemical decomposition.
14. When a more reactive element displaces a less reactive element from its aqueous salt solution, the reaction which takes place is called chemical displacement.
15. When an acid solution reacts with a base or metal carbonate, so as to form a salt, then the reaction is called neutralisation reaction.
16. The process of separation of pure crystals of a substance from its hot and supersaturated (concentrated) solution on cooling is called crystallisation.

Haryana State Board HBSE 7th Class Science Solutions Chapter 5 Acids, Bases and Salts Textbook Exercise Questions and Answers.

Haryana Board 7th Class Science Solutions Chapter 5 Acids, Bases and Salts

HBSE 7th Class Science Acids, Bases and Salts Textbook Questions and Answers

Question 1.
State differences between acids and bases.
Answer:

Question 2.
Ammonia is found is many household products, such as window cleaners. It turns red litmus blue, what is its nature?
Answer:
Basic.

Question 3.
Name the source from which litmus solution is obtained. What is the use of this solution?
Answer:
Litmus solution is extracted from lichens. It has a mauve (purple) colour in distilled water. When added to an acidic solution, it turns red and when added to a basic solution, it turns blue. It is available in the form of a solution, or in the form of strips of paper.

Question 4.
Is the distilled water acidic/basic/ neutral? How would you verify it?
Answer:
The distilled water is neutral. Put a drop of the distilled water on a strip of the red litmus paper with the help of a droper. We observe that colour of the litmus paper as not change.

The solutions which do not change the colour of either red or blue litmus are known as neutral solutions. These substances are neither acidic nor basic.

Question 5.
Describe the proeess of neutralization with the help of an example.
Answer:
The process due to! which an acid completely reacts with a base to form salt and water as the only products is called neutralization.
Acid + Base → Salt + Water
Example: Hydrochloric add (HCl) + Sodium hydroxide (NaOH)
Sodium chloride (NaCl) + Water (H₂O)

Question 6.
Make “T” if the statement is true and ‘F’ if it is false.
(i) Nitric acid turn red litmus blue.
(ii) Sodium hydroxide turns blue litmus red.
(iii) Sodium hydroxide and hydrochloric acid neutralise each other and form salt and water.
(iv) Indicator is a substance which shows different colours in acidic and basic solutions.
(v) Tooth decay is caused by the presence of a base.
Answer:
(i) Flase
(ii) Flase
(iii) True
(iv) True
(v) True.

Question 7.
Dorji has a few bottles of soft drink in his restaurant. But unfortunately, these are not labelled. He has to serve the drinks on the demand of customers. One customer wants acidic drink, another wants basic and third one wants neutral drink; How will Dorji decide which drink is to be served to whom?
Answer:
Do yourself.

Question 8.
Explain why?
(a) An antacid tablet is taken when you suffer from acidity.
(b) Calamane solution is applied on the skin when an ant bites.
(c) Factory waste is neutralised before disposing it into the water bodies.
Answer:
(a) Our stomach contains hydrochloric acid. It help us to digest food. But too much of acid in the stomach causes indigestion. Sometimes indigestion is painful. To relieve indigestion, we take an antacid such as milk of magnesia, which contains magnesium hydroxide. It neutralises the effect of excessive acid.

(b) The sting of an ant contains formic acid. When an ant bites, it injects the acidic liquid into the skin. The effect of the sting can be neutralised by rubbing moist baking soda (sodium hydrogen carbonate) or calamine solution, which contains Zinc carbonate.

(c) The wastes of many factories contain acids. If they are allowed to flow into the water bodies, the acids will kill fish and other organisms. The factory wastes are, therefore, neutralised by adding basic substances.

Question 9.
Three liquids are given to you. One is hydrochloric acid, another is sodium hydroxide and third is a sugar solution. How will you Identify them? You have only turmeric indicator.
Answer:
Do yourself.

Question 10.
Blue litmus paper is dipped in a solution. It remains blue. What is the nature of the solution? Explain.
Answer:
The nature of the solution is neutral, because the solutions which do not change the colour of either red or blue litmus are known as neutral solution. These substances are neither acidic nor basic.

Question 11.
Consider the following statements:
(a) Acids and bases both change colour of all indicators.
(b) If an indicator gives a colour change with an acid, it does not give a change with a base.
(c) If an indicator changes colour with a base, it does not change colour with an acid.
(d) Change of colour in an acid and a base depends on the type of the indicator. Which of these statements are correct?
(i) All four
(ii) a and b
(iii) b and c
(iv) only d
Answer:
(ii) a and b.

Extended Learning – Activities And Projects

Question 1.
Using the knowledge of acids and bases, write a secret message with the help of baking soda and beet’root. Explain how it works.
(Hint: Prepare baking soda solution in water. Use this solution to write the message on a sheet of white paper with a cotton bud. Rub a slice of fresh beet root over the message.)
Answer:
Do yourself.

Question 2.
Prepare red cabbage juice by boiling a piece of red cabbage in water. Use it as an indicator and test the acidic and’ basic solutions with it. Present your observations in the form of a Table.
Answer:
Do yourself.

Question 3.
Bring the soil sample of your area, find out if it is acidic, basic or neutral. Discuss with farmers if they treat the soil in any manner.
Answer:
Do yourself.

Question 4.
Visit a doctor. Find out the medicines be prescribes to treat acidity. Ask him how acidity can be prevented.
Answer:
Do yourself.

HBSE 7th Class Science Acids, Bases and Salts Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is an acid Id
Answer:
A substance which dissolves in water to give hydrogen ions as the only positively charged ions’fs called an acid.

Question 2.
What are mineral acids? Give, three examples.
Answer:
The acids which are prepared from the minerals of the Earth are called mineral acids.
Examples: Sulphuric acid, Nitric acid, Hydrochloric acid.

Question 3.
What are organic acids? Give three examples.
Answer:
Organic acids are found in plant and animal products, for examples, oxalic acids, citric acid, acetic acid, etc.

Question 4.
A solution turns red litmus solution blue. Is the solution acidic or basic in nature?
Answer:
Basic.

Question 5.
Give two examples each of (i) Strong bases (ii) Weak bases.
Answer:
(i) Strong bases: Sodium hydroxide, potassium hydroxide.
(ii) Weak bases: Copper hydroxide, zinc hydroxide. .

Question 6.
What do you understand by the term “neutral substance?”
Answer:
The substances which do not bring about any change in the colour of common indicators are called neutral substances.

Question 7.
Name the acids present in:
(i) Vinegar
(ii) Lemon juice
Answer:
(i) Acetic acid (CH₃COOH)
(ii) Citric acid.

Question 8.
Write the names of three mineral acids.
Answer:
(i) Sulphuric acid (H₂SO₄)
(ii) Nitric acid (HNO₃) and
(iii)Hydrochloric acid (HCl) are mineral acids.

Question 9.
Which of the following are oxides?
H₂O, CO, Co, NO, CO₂ , NaOH
Answer:
Oxides: H₂O, CO, NO and CO₂.

Question 10.
From the following list select metallic oxide and non-metallic oxides: CaO, Fe₂O₃, N₂O₅, CO₂, Na₂O, SO₂.
Answer:
(i) Metallic oxide: CaO, Fe₂O₃ and Na₂O.
(ii) Non-metallic oxide: N₂O₅, CO₂ and SO₂.

Question 11.
What are indicators?
Answer:
The complex, naturally occurring substances, which change their colour on coming in contact with other substances are called indicators. Turmeric, litmus, china rose etc. are some indicators.

Question 12.
Name two neutral liquids.
Answer:
(i) Alcohol
(ii) Ether.

Question 13.
Name two neutral gases.
Answer:
(i) Hydrogen, (ii) Oxygen.

Question 14.
Name two neutral solids.
Answer:
(i) Common Salt
(ii) Sugar.

Question 15.
What do you understand by term concentrated acid?
Answer:
The acids which contain very little or no amount of water are called concentrated acids.

Question 16.
What are dilute acids?
Answer:
The acids which contain a large amount of water (or solutions of acids in water) are called dilute acids.

Question 17.
Name the kind of substance formed when an acid reacts with a base.
Answer:
Neutralised.

Question 18.
What is missing in the following equation?
Fat + ……. → Soap + Glycerol
Answer:
Fat + NaOH → Soap + Glyceral
Thus NaOH missing from the equation.

Question 19.
An element combines with oxygen to form an oxide. This oxide dissolves in water. This aqueous solution changes blue litmus to red. Write:
(i) The nature of element (metal or non-metal)
(ii) The general name of the oxide.
Answer:
(i) The element is non-metal.
(ii) General name of the oxide non-metallic oxide.

Question 20.
What happens when a non-metal oxide is dissolved in water?
Answer:
When a non-metal oxide is dissolved in water, it forms acids. Examples:
(i) CO₂ + HO₂ → H₂CO₃ (Carbonic acid).
(ii) SO₂ + HO₂ → H₂SO₃(Sulphuric acid).

Question 21.
State one characteristics, property of all acids.
Answer:
All acids contain replaceable hydrogen.

Question 22.
Name the gas obtained when a metal carbonate reacts with an acid.
Answer:
When a metal carbonate reacts with an acid, carbon dioxide gas is envolved. Example:

Question 23.
Write equations for the action of water on:
(i) MgO
(ii) Calcium oxide.
Answer:
(i) MgO + H₂O → Mg(OH)₂ (Magnesium hydroxide)
(ii) CaO + H₂O → Ca(OH)₂(Calcium hydroxide)

Question 24.
What are mineral acids? Give two examples.
Answer:
Mineral acids are those acids which are obtained from the earth. Examples, Sulphuric acid, Nitric acid.

Question 25.
Name the three salts which are commonly lised at home..
Answer:
Three, salts commonly used at home are:
(i) Sodium chloride
(ii)Sodium carbonate
(iii) Sodium hydrogen carbonate.

Question 26.
Give the chemical formula of slaked lime
Answer:
Chemical formula of slaked lime is Ca(OH)₂

Question 27.
Name one/compound of calcium which is used for bleaching cloth.
Answer:
Bleaching powder.

Question 28.
What is the formula of sulphuric acid?
Answer:
The formula of sulphuric acid is H₂SO₄.

Question 29.
A solution turns red litmus paper blue. What does this indicate about the chemical nature of the solution?
Answer:
The chemical nature of the solution is acidic.

Question 30.
What do you understand by anhydrous salt?
Answer:
Hydrated salts loose their water of crystallisation upon heating. They love their shape and colour also and becomes powered. They are called anhydrous salts.

Question 31.
Name two normal salts.
Answer:
(i) Sodium Chloride (NaCl)
(ii) Potassium nitrate (KNO₃).

Question 32.
Name two basic sdlts.
Answer:
(i) Calcium hydrdgen chloride [Ca(OH)Cl]
(ii) Magnesium hydroxy chloride [Mg(OH)Cl] etc.

Question 33.
Write the balanced chemical equations for the reaction that takes place when zinc, magnesium and sodium react with dilute hydrochloric acid.
Answer:
Reaction of hydrochloric acid (dil.) with Zn, Mg, and Na:
(i) Zn + 2HCl → ZnCl₂ + H₂
(ii) Mg + 2HCl → MgCl₂ + H₂
(iii) 2Na + 2HCl → 2NaCl + H₂

Question 34.
Write two uses of slaked lime.
Answer:
Uses of slaked lime:
(i) It is used in manufacture of bleaching powder.
(ii) It is used as an important building materials

Question 35.
Complete the following equations:
(i) CO₂ + H₂O → ……………..
(ii) CO₂ + 2Na0H → …………….. + ……………..
(iii) SO₂ + H₂O → ……………..
(iv) MgO + H₂SO₄ → …………….. + ……………..
(v) CaC0₃ + 2HCl → …………….. + ……………..
(vi) Na₂O + H₂O → ……………..
(vii) 2NaOH + H₂SO₄ → …………….. + ……………..
(viii) NaOH + HNO₃ → …………….. + ……………..
(ix) CaO + H₂SO₄ → …………….. + ……………..
(x) MgO + 2HCl → ……………..
Answer:
(i) CO₂ + H₂O → H₂CO₃ (carbonic acid)
(ii) CO₂ + 2Na0H → Na₂CO₃ + H₂O (sodium carbonate)
(iii) SO₂ + H₂O → H₂SO₃ (suiphurous acid)
(iv) MgO + H₂SO₄ → MgSO₄ + H₂O (magnesium sulphate)
(v) CaC0₃ + 2HCl → CaCl₂ + H₂O + CO₂ (Calcium Chloride)
(vi) Na₂O + H₂O → 2Na0H (sodium hydroxide)
(vii) 2NaOH + H₂SO₄ → Na₂SO₄ + H₂O (sodium suphate)
(viii) NaOH + HNO₃ → NaNO₃ + H₂O (sodiùm nitrate)
(ix) CaO + H₂SO₄ → CaSO₄ + H₂O (calcium sulphate)
(x) MgO + 2HCl → MgCl₂ +H₂O

Short Answer Type Questions

Question 1.
How can you test the presence of an acid in any substance?
Answer:
Acid can be tested in any substance by the following methods:
(i) Take a drop of the dilute solution of the substance on the tips of your tongue. If tastes sour, it is acidic.
(ii) Dip a blue litmus paper in the solution. If ‘ the colour of the litmus paper turns red, the solution is acidic.

Question 2.
What are organic acids? Give two examples.
Answer:
Soured milk, Lemon, Green mangoes and Karvanda are sour testing. All of them contain some naturally occuring acids. Such acids are also found in humans and plants materials. They are known as organic acids. The acids such as lactic acid, citric acid, tartaric acid and acetic acid are naturally occuring and known as organic acid.

Question 3.
What are the uses of mineral acids in industry?
Answer:
Use of’mineral acids in industry:
(i) Concentration sulphuric acid, nitric acid and hydrochloric acid are used in a large number of metallurgical operations, manufacture of fertilizers and preparations of large number of industrial chemicals.
(ii) Hydrochloric acid is used for removing the deposits from inside the boilers. This process is known as de-scaling.

Question 4.
What are indicators? Name two acid-base indicators.
Answer:
The substances which are used to identify whether a substance is an acid or base is called indicators. For example, litmus solutions give red colour with acids and blue colour with bases. Therefore, litmus is used as indicators. Substances which give different colours with acid and base are called acid-base indicators, for examples. Methyl orange, phenolphthalein.

Question 5.
What are acid salts? Give two examples.
Answer:
The salts which dissolves water to produce a solution, which behaves like an acid is called an acid salt.
Examples: Sodium hydrogen carbonate (NaHCO₃), Potassium hydorgen carbonate (KHCO₃), Sodium hydrogen sulphate etc.

Question 6.
How is potash alum prepared?
Answer:
A mixture of potassium sulphate and aluminium sulphate is dissolved in water and then the solution is concentrated. Potash alum is formed. It separates out as crystals.

Question 7.
Why are sodium bicarbonate and lemon juice used during indigestion?
Answer:
Sodium bicarbonate neutralizes the acidity in the stomach. Hence, it is used during indigestion. Lemon contains acid. It reacts with undigested food and softens it. Thus, lemon is also used in indigestion.

Question 8.
Why are brass vessels coated with tin or kalai?
Answer:
When brass vessels are used to cook food with tamarind or lemon juice, the acids present in it reacts with brass metal and corrode it. The kalai layer protects this vessels from the action of acids. Due to this reason brass vessels are coated with tin.

Question 9.
What is salt? Name any salts and give thier formulae.
Answer:
A substance formed by the neutralisation of an acid with a base is called salt.
Examples:
(i) Potassium nitrate (KNO₃)
(ii) Sodiun: nitrate (NaNO₃)
(iii) Calcium carbonate (CaCO₃)
(iv) Zinc sulphate (ZnSO₄)
(v) Copper sulphate (CuSO₄).

Question 10.
Define an acid. Give three properties of acids.
Answer:
An acid is a substance which when dissolved in water gives hydrogen ions. Examples: H₂SO₄, HNO₃ and HCl etc.
Properties of acids:
(i) They have a sour taste
(ii) They turn blue litmus solution red.
(iii) They have replaceable hydrogen ion.

Question 11.
What are bases? Mention three properties of alkalies.
Answer:
The substance which react with acids to form salt and water only are called bases. Examples: Cu(OH)₂, Fe(OH)₃, Pb(OH)₂ etc.
Properties of alkalies:
(i) They tarn red litmus paper blue
(ii) They have a better taste.
(iii) They turn methyl orange from pink to yellow.

Question 12.
What are the uses of sodium bicarbonate?
Answer:
Uses of sodium bicarbonate:
(i) It is used in medicines to neutralise the acidity in the stomach.
(ii) It is used as backing power.
(iii) It is used in fire extinguisher.

Question 13.
What are the uses of common salt?
Answer:
Uses of common salt:
(i) It is an essential constituents of our diet.
(ii) It is used in the manufacture of soap.
(iii) It is used for glazing pottery. .
(iv) It is a starting material for the manufacture of chlorine, hydrochloric acid, washing soda and sodium hydroxide.
(v) It is used as food preservatives.
(vi) It turns freezing mixture with ice.

Question 14.
Give five uses of potassium nitrate.
Answer:
Uses of potassium nitrate:
(i) It is used in the manufacture of gun powder.
(ii) It is used in making fire works.
(iii) It is used in refrigeration.
(iv) It is used as fertilizers.
(v) It is used in glass industry.

Question 15.
Which acids is called ‘the king of the acids’? Give its uses.
Answer:
Sulphuric acid (H₂SO₄) is called “the king of the acids”.
Uses of sulphuric acid:
(i) It is used in the manufacture of detergents.
(ii) It is used as a dehydrating agent.
(iii) It is used in storage batteries.
(iv) It is used in petrol refining.
(v) It is used in textile, paper and leather industry.
(vi) It is used in fertilizers industry for the manufacture of ammonium sulphate and superphosphate of lime.

Question 16.
Explain with the help of chemical equations how the following acids are formed?
Carbonic acids, Sulphurous acid, Phosphoric acid.
Answer:
(i) Carbonic acid is prepared by dissolving carbon dioxide in water.
CO₂ + H₂O → H₂CO₃ (Carbonic acid)

(ii) Sulphurous acid is formed by dissolving sulphur dioxide in water.
SO₂ + H₂O → H₂SO₃ (Sulphurous acid)

(iii) Phosphoric acid is prepared by dissolving phosphorus pentaoxide in hot water.
P₂O₅ + 3H20 → 2H₃PO₄ (Phosphoric acid)

Acids, Bases and Salts Class 7 HBSE Notes

1. Curd, lemon juice, orange juice and vinegar taste sour. These substances taste sour because they contain acids. The chemical nature of such substances is acidic. The word acid comes from the Latin word acere which means sour. The acids in these substances are natural acids.
2. A substance which produces hydrogen (H⁺) ions when dissolved in water is called an acid. This definition was given by Arrhenius, a Swedish Chemist in 1912.
3. The acids which are prepared from the minerals of the Earth are called mineral acids.
Examples of Mineral Acids

4. The acids which dissolve in water to give a large number of positively charged hydrogen ions are called strong acids.
Examples of Strong Acids : Sulphuric acid, nitric acid, hydrochloric acid and phosphoric acid are examples of strong acids.
5. The acids which dissolve in water to give a small number of positively charged hydrogen ions are called weak acids.
Examples of Weak Acids : Carbonic acid, acetic acid, sulphurous acid, formic acid, etc., are examples of weak acids. In fact, most of the organic acid are weak acids.
6. The acids which contain very little or no amount of water are called concentrated acids.
7. The acids which contain a large amount of water (or solutions of acids in water) are called dilute acids.
8. General Physical Properties of Acids
(i) They have a sour taste.
(ii) They turn blue litmus solution red.
(iii) They turn methyl orange solution pink.
(iv) They do not affect phenolphthalein solution.
(v) Strong acids have a corrosive action on skin. They cause painful blisters.
(vi) Most of the acids are soluble in water.
(vii) Acids solutions are conductors of electricity.
9. Uses of Acids

10. The substances which react with acids to form salt and water as only products are called bases. All oxides of metals are bases. All hydroxides of metals are bases.
11. All bases which are soluble in water are called alkalis.
12. Strong bases completely dissociate in aqueous solution. For example, sodium hydroxide (NaOH), potassium hydroxide (KOH), etc.
13. They undergo partial dissociation in aqueous solution. For example, copper hydroxide Cu(OH)₂, Zinc hydroxide Zn(OH)₂, etc.
14. The bases show the following properties:
(i) These have a bitter taste.
(ii) Bases neither have colour nor small. Only Ammonium hydroxide (NH₄OH) has a pungent smell.
(iii) The basic solutions are soapy to touch, i.e., if little amount of sodium hydroxide is rubbed on fingers, it would give a feeling as if soap has been applied on the fingers.
(iv) Bases turn red litmus blue.
(v) Bases contain hydroxide ions e.g., Sodium hydroxide is represented as NaOH, calcium hydroxide is represented as Ca(OH)₂, etc., where OH is the hydroxy group.
(vi) Bases react with acids to give salt and water.
15. Uses of Bases

16. Special type of substances are used to test whether a substance is acidic or basic. These substances are known as indicators. Turmeric, litmus, china, rose, petals (Gudhal), etc., are some of the naturally occurring indicators.
17. The reaction between an acid and a’base-is known as neutralisation. Salt and water are produced in this process with the evolution of heat.
Acid + Base → Salt + Water (Heat is evolved)
The following reaction is an example :
Hydrochloric acid (HCl) + Sodium hydroxide (NaOH) → Sodium chloride (NaCl) + Water (H₂O)

Haryana State Board HBSE 7th Class Science Solutions Chapter 4 Heat Textbook Exercise Questions and Answers.

Haryana Board 7th Class Science Solutions Chapter 4 Heat

HBSE 7th Class Science Heat Textbook Questions and Answers

Question 1.
State similarities and differences between the laboratory thermometer and the clinical thermometer.
Answer:
Laboratory Thermometer: While performing experiments involving the measurement of temperature in the laboratory, a mercury thermometer is used. It is a thermometer having graduations marked on the Celsius scale from 0°C to 100°C.

The difference between the lower and upper fixed points is called range of the thermometer. The range of a mercury thermometer is 100°C. A mercury thermometer having graduations from 0°C to 100°C is shown in figure 4.8.

Clinical Thermometer:
To measure the temperature of a person running fever, doctor uses a thermometer known as Clinicdl Thermometer. It is a specially designed mercury thermometer and is used in the clinics and hospitals by doctors to measure human body temperature.

In construction, it differs from laboratory thermometers, in the sense that a kink or constriction is provided in the stem just above the bulb. Because of this kink, mercury doesn’t fall back into the bulb when clinical thermometer is taken out of the mouth of a patient to know the temperature. A jerk is given to the thermometer so that it is set again for measuring human body temperature. The temperature interval marked on the clinical thermometers ranges from 35°C to 43°C.

Question 2.
Give two examples each of conductors and insulators of heat.
Answer:
Conductors: aluminium, iron
Insulators: plastic, wood

Question 3.
Fill in the blanks:
(a) The hotness of an object is, is determined by its …………… .
(b) Temperature of boiling water cannot be measured by a …………… thermometer.
(c) Temperature is measured in degree ……………. .
(d) No medium is required for transfer of heat by the process of ………….. .
(e) A cold steel spoon is dipped in a cup of hot milk. It transfers heat to its other end by the process of …………. .
(f) Clothes of …………… colours absorb heat better than clothes of light colours.
Answer:
(a) Touching
(b) Clinical
(c) Celsius
(d) Radiation
(e) Conduction
(f) Dark

Question 4.
Match the following:

Answer:

Question 5.
Discuss why wearing more layers of clothing of during winter keeps us warmer tljian wearing just one thick piece of clothing?
Answer:
More layers of clothing keep us warm in winters as they have a lot of space between them. This space gets filled up with air. As air is a bad conductor, it does not allow the body heat to escape out.

Question 6.
Look at Fig. 4.10. Mark where the heat is being transferred by conduction, by convection and by radiation.
Answer:

Question 7.
In places of hot climate it is advised that the outer walls of houses be painted white. Explain.
Answer:
In places of hot climate it is advised that the outer wail of houses be painted white because white colour do not radiate heat easily.

Question 8.
One litre of water at 30°C is mixed with one litre of water at 50°C. The temperature of the mixture will he:
(a) 80°C
(b) More than 50°C but less than 80°C
(d) 20°C
(d) Between 30°C and 50°C
Answer:
(b) More than 50°C but less than 80°C

Question 9.
An iron ball at 40°C is dropped in a mug containing water at 40°C. The heat will:
(a) Flows from iron ball to water.
(b) Not flow from iron ball to water or from water to iron ball.
(c) Flows from water to iron ball.
(d) Increase the temperature of both.
Answer:
(a) flows from iron ball to water.

Question 10.
A wooden spoon is dipped in a cup of ice-cream. Its other end:
(a) Becomes cold by the process of conduction.
(b) Becomes cold by the process of convection.
(c) Becomes cold by the process of radiation.
(d) Does not become cold.
Answer:
(d) does not become cold.

Question 11.
Stainless steel pans are usually provided with copper bottoms. The reason for this could be that:
(a) Copper bottom makes the pan more durable.
(b) Such pans appear colourful.
(c) Copper is a better conductor of heat than the stainless steel.
(d) Copper is easier to clean than the stainless steel.
Answer:
(c) Copper is a better conductor of heat than the stainless steel.

Extended Learning – Activities And Projects

Question 1.
Go to a doctor or your nearest health centre. Observe the doctor taking temperature of patients. Enquire:
(a) Why he/she dips the thermometer in a liquid before use.
(b) Why the thermometer is kept under the tongue.
(c) Whether the body temperature can be measured by keeping the thermometer at some place other than mouth.
(d) Whether the temperature of different parts of the body is the same or different. You can add m.ore questions which come to your mind.
Answer:
Do yourself. You can take help of your family doctor.

Question 2.
Go to a veterinary doctor (a doctor who treats animals). Discuss and find out the normal temperature of domestic animals and birds.
Answer:
Do yourself.

Question 3.
Wrap a thin paper strip tightly around an iron rod. Try to burn the paper with candle while rotating the iron rod continuously. Does it burn? Explain your observation.
Answer:
Do yourself.

Question 4.
Take two similar transparent glass bottles having wide mouths. Put a few crystals of potassium permaganate or pour a few drops of ink in one bottle. Fill this bottle with hot water. Fill the other bottle with cold water. Cover the cold water bottle with a thick piece of paper such as a postcard. Press the postard firmly with one hand and hold the bottle with the other hand. Invert the bottle and place it on top of the hot water bottle. Hold both the bottles firmly. Ask some other person to pull the postcard. Observe what happens. Explain.
Answer:
Do yourself.

HBSE 7th Class Science Heat Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is heat?
Answer:
The energy transferred from one body to another body due to a temperature difference between them is called heat.

Question 2.
Define temperature.
Answer:
Temperature is the degree of hotness or coldness of a body.

Question 3.
Define thermometer.
Answer:
A device used for measuring the temperature of different objects is called a thermometer.

Question 4.
Hot water bottles are used for fermentations. Explain why?
Answer:
Hot water bottles are used for fermentation as the water does not cool quickly due to its large specific heat capacity.

Question 5.
When equal amount of air, iron and oil are heated from 15°C to 25°C. List them in the order of increasing expansion.
Answer:
Iron, oil, air.

Question 6.
Name any four substances which expand on heating.
Answer:
Aluminium, steel, iron and copper.

Question 7.
Name any two substances which have negligible changes in length on heating.
Answer:
Pyrex glass, Invar.

Question 8.
Name two substances which contract on heating?
Answer:
Ice, Bismuth.

Question 9.
Do all liquids expand when heated or is there any exception?
Answer:
Yes, below 4°C when heated, water contract in stead of expanding.

Question 10.
Which substances has the highest heat capacity?
Answer:
Water.

Question 11.
What is the temperature of a normal human being on the Celsius scale?
Answer:
The temperature of a normal human being on the Celsius scale is 37°C.

Question 12.
Name the thermometer used for measuring the temperature of the human body.
Answer:
The thermometer used to measure the temperature of a human body is called clinical thermometer.

Question 13.
Define convection.
Answer:
The phenomenon due to which particles of a medium actually move to the source of heat energy and then move away from it after absorbing heat energy is called convection.

Question 14.
Why is convection not possible in solids?
Answer:
The molecules of a solid are held strongly due to intermolecular forces. As these molecules cannot travel to the source of heat energy, convection is not possible in case of solids.

Question 15.
What is ventilation?
Answer:
The process by which impure and warm air inside a room is continuously replaced by fresh air from outside is called ventilation.

Question 16.
What do you understand from the term lower standard point?
Answer:
The 0°C correspondence to the temperature of pure melting ice and is called the lower standard point.

Question 17.
What do you understand by upper standard point?
Answer:
100°C corresponds to the temperature of pure boiling water and is called the upper standard point.

Question 18.
Define conduction.
Answer:
The process of transmission of heat energy in solids without the actual movement of particles from their position is called conduction.

Question 19.
Give two examples to show that heat caused biological changes.
Answer:
(i) Conversion of ‘gur’ into alcohol.
(ii) Conversion of milk into curd.

Question 20.
Why is ice wrapped in gunny bags?
Answer:
Gunny bags have a number of fine pores, filled with air. Air being a bad conductor of heat does not allow the external heat to go in and melts the ice.

Question 21.
Why is tea generally served in China clay cups and plates?
Answer:
Because the China clay is bad conductor of heat and checks the heat conduction from the tea to the surroundings and thus keeps the tea hot.

Question 22.
By which of the processes (conduction, convection, radiation), it is not possible to transfer heat?
(i) In a vacuum
(ii) Through the solid material.
Answer:
(i) Conduction and convection
(ii) Convection and radiations.

Question 23.
Why do we use cooking utensils made of metals and alloys?
Answer:
Metals and alloys are good conductors of heat so that the heat from the flame is conducted to the food inside quickly and efficiently.

Question 24.
Is medium necessary for the transference of heat by radiations?
Answer:
No, medium is not necessary for the transference of heat by radiation.

Question 25.
Why do we feel warm while standing beside a burning furnace?
Answer:
When we stand beside a burning furnace, we feel warms, because of the heat radiation coming from the furnace.

Question 26.
Firemen wear helmets made from brass polished from outside. Why?
Answer:
Brass polished helmets reflects most of the heat and absorbs only a very little part of it when they fight against a fire.

Question 27.
When does the conduction of heat stop in two bodies in contact?
Answer:
The conduction of heat stops in two bodies in contact when both attain the same (equal) temperature. In this position they have no temperature difference.

Question 28.
Why is the handle of a press made of ebonite or wood?
Answer:
The handle of press is made of ebonite or wood, because ebonite and wood are bad conductors of heat. So the heat does not reach in our body.

Question 29.
Define radiation.
Answer:
The transfer of heat energy from a hot body to a cold body directly, without heating the space in between the two bodies is called radiation.

Question 30.
Define insulators.
Answer:
The materials which do not allow heat to pass through them easily are poor conductors of heat such as plastic and wood. Poor conductors are known as insulators.

Question 31.
What is thermos flask?
Answer:
Thermos flask is a device in which heat losses due to conduction, convention and radiation are minimised.

Short Answer Type Questions

Question 1.
The cooking utensils are made of metals like aluminium or copper while their handles are made of wood. Why?
Answer:
The cooking utensils are made of metals like aluminium or copper because these metals are good conductors of heat so they help in the transfer of heat.

The handles of cooking utensils are made up of bad conductors such as wood, plastic etc. As the handles made of bad conductors do not get heated up while cooking, we can hold them easily.

Question 2.
Kites and eagles fly without flapping their wings. Why?
Answer:
During the day, hot air surrounding the land gradually rises up and a convection air current develops. Kites and eagles move along this rising current without flapping the wings to fly high up in the sky.

Question 3.
Why do the birds puff up their feathers in winter?
Answer:
The birds puff up their feathers in winter, because in doing so they trap large amount of air, which in turn acts as an insulator and does not allow their body heat to flow out.

Question 4.
Explain briefly the formation of air currents.
Answer:
In coastal areas, during the day, the cool air blows from sea towmrds the land called sea breeze. During the night, the cool air blows from land to sea called the land breeze. This happens because of convection air currents. At night, land cools down much faster than sea. So, sea is warmer than land and the air current blows from land to sea. During the day, land is hotter than sea. As a result, the air rises up and cold air from sea blows towards the land to take its place.

Question 5.
Cement or concrete floors are made in pieces with metals or glass strips in between. Give reasons.
Answer:
It is done to allow for the expansion in summer and contraction in winter. If cement or concrete floors are made out in one continuous pieces. It would develop crackes due to contraction and expansion.

Question 6.
Room heaters have shiny reflectors. Why?
Answer:
Room heaters have shiny reflectors as the shiny surface absorbs very little heat. They reflect all the heat which makes the room heaters more effective.

Question 7.
Why is the handle of a pressure cooker covered with thick plastic?
Answer:
The handle of a pressure cooker covered with thick plastic, because plastic is a bad conductor of heat. Hence, the heat from the hot cooker does not flow to the handle, with the result that we can hold easily.

Question 8.
The desert sand is very hot in the day and very cool at night. Why?
Answer:
The desert sand has low specific heat capacity. So sand gets very hot in day time. During the night sand cools more quickly due to cold air which moves towards the sea.

Question 9.
Why is the handle of a metallic kettle covered with strips of cane?
Answer:
Cane strips is bad conductor of heat. Therefore, it cannot get heated when water is boiled in kettle. Therefore, the handle of a metallic kettle is covered with cane strips.

Question 10.
Why does the handle of an iron made of ebonite or wood?
Answer:
Ebonite or wood is a bad conductor of heat. Therefore, the heat from the iron is not conducted to the hand.

Question 11.
How does a blanket keep you warm in a cold night, even though it is not a source of heat?
Answer:
The blanket is made of wool, which is a bad conductor of heat. It has fine pores in which air is trapped which is also a bad conductor of heat. They do not allow heat to escape from our body to the surroundings. Therefore, the blanket keeps our body warm in winter.

Question 12.
Why are cloudy nights warmer than the clear nights?
Answer:
Cloudy nights are warmer than clear nights due to the fact that the heat which is radiated by the earth is again reflected back by the clouds. While on the other hand this phenomenon is not possible when the night is clear.

Question 13.
How are had conductors of heat useful in our daily life?
Answer:
Bad conductors are used for holding hot utensils in the kitchen. Bricks and mud which are bad conductors are used in building houses, especially in the ruler. regions. They keep houses warm in winter and cool in summer. The feathres of birds, hair and fur of animals keep them warm in winter, as they are bad conductor of heat.

Question 14.
Why do we wear woolen clothes in winter?
Answer:
Woolen clothes have fine pores filled with air. Wool and air are bad conductors of heat They do not allow heat of our bodies to escape out. Therefore woolen cloth keep the body warm in winter. And for the same reason we wear woolen cloth in winter.

Long Answer Type Questions

Question 1.
Describe briefly the process of conduction.
Answer:
Heat travels through solids by conduction only. The process of transmission of heat energy in solids without the actual movement of particles from their position is called conduction. Conduction takes place under the following conditions:
(i) A material medium that is compact.
(ii) No movement of any particle in the medium.
Thus, solids transmit heat though conduction. When a solid substance is heated, the particles that become hot start vibrating and pass on the excess energy to the neighbouring particles. This process continues till the whole body is heated. However during such an energy transfer, a particle does not change its position. Hence, heat is carried without the bodily movement of the particles.

There are some solids which allow the heat to pass through them. Such substances are called the conductors. Almost all metals such as iron, copper, silver, aluminium etc. are good conductors. The substances which do not allow the heat to pass through them are called the insulators. Wood, plastic, wool, clay etc. are bad conductors.

Question 2.
Write an experiment to prove that heat radiations can travel through vacuum.
Answer:
Take a flat bottomed flask. In the mouth of the flask fix a rubber stopper having two holes. Pass a thermometer through one hole and a glass tube with stopper through the other hole.

Remove air from the flask, by connecting to a vacuum pump. Record the temperature from the thermometer. Place the flask in bright sunlight or in front of an electric heater. It is observed that the thermometer records a rise in temperature. Thus, the experiment proves that transference of heat by radiaton requires no medium.

Question 3.
Explain the working of a thermos flask.
Answer:
Thermos flask is a special kind of flask for keeping liquids. It prevents loss or gain of heat by any of the three methods. It keeps liquid warm or cold for a long time. It was invented by Sir James Dewan in 1893.

It consists of a double-walled glass-cylinder. A vacuum is created in the space between the double walls. The two inner surfaces of glass walls are silvered. The flask is placed on a spring within a non-conduction cylindrical case to protect it from jerks and breakages. The gaps between flask and outer casing is packed with felt pads. The mouth of the flask is finally closed with a cork.

Since the container is made of glass which is a bad conductor of heat and therefore, the loss or gain of heat due to conduction is prevented. As there is vacuum between the double walls, it prevents transmission of heat by convection. Due to silvering of the inner surfaces, the heat loss by radiation is prevented. The cork and the felt pads also help to preserve the heat inside the flask. So, the hot liquids like tea, coffee, etc. remain hot and cold liquids like water, juice, etc. remain cold for a long time.

Question 4.
Write five applications of radiation.
Answer:
Applications of radiation:
(i) The base of cooking utensils is painted black so that it can absorb more heat and hence cooking is done fast.
(ii) Dark clothes are worn in winters as they absorb more heat from the sunlight and keep our body warm.
(iii) White clothes are worn in summer as they absorb very little heat and keep us cool.
(iv) Room-heaters have shiny reflectors as the shiny surface absorbs very little heat. They reflect all the heat which makes the room- heaters more effective.
(v) Crockeries are polished and painted white from outside so that they do not radiate heat easily.

Question 5.
Describe the process of radiation. How is it different from conduction and convection?
Answer:
Radiation is a process of transmission of heat in which heat energy travels in straight lines from hotter to cooler regions without the help of any intervening medium. It means that this process is different from the other two as it does not need any medium like conduction or convection. Radiation can take place in a vaccum. For example, heat from the sun reaches us through the outer space (vacuum) by means of radiation in the form of electromagnetic waves.

Differefnbe between radiation, conduction and convection:

Heat Class 7  HBSE Notes

• Our sense of touch is not always a reliable guide to the degree of hotness of an object.
• Heat: Heat is a form of energy which produces in us sensation of warmth. It causes hotness or coldness sensation in our body.
• Temperature: Temperature tells how hot a body is? Temperature of a body is the degree of hotness or coldness of the body.
• Heat flows in the direction of fall of temperature. Heat can be converted to other forms of energy like sound, light, mechanical energy etc. Other forms of energy can also be converted to heat energy.
• Effects of heat:
  (i) The object becomes hot.
  (ii) The object may expand in size.
  (iii) The object may change in state.
  (iv) Heat can speed up chemical reaction.
• Temperature is measured by a device called thermometer.
• The thermometer that measure our body temperature is called a clinical thermometer. The range of this thermometer is from 35°C to 42°C. For other purposes, we use the laboratory thermometers. The range of these thermometers is usually from 10°C to 110°c.
• The laboratory thermometer used in laboratories. It is called Celsius thermometer. It has one hundred markings on it.
• The melting point of pure ice is called lower standard point. Its value is 0°C.
• The boiling point of pure water is called upper standard point. Its value is 100°C.
• Transfer of heat: Heat flows from one body to another body by temperature difference. The flow of heat is from higher temperature to lower temperature. There are three different ways of heat transfer: conduction, convention and radiations.
• Conduction of heat: The process in which heat is handed over from one particle to another in the direction of fall of temperature without the actual movement of the particles of the medium is called conduction.
  
• Good conductor of heat: The materials which allow heat to pass through them easily, are called good conductor of heat. For example, silver, copper, aluminium, mercury etc. are good conductors of heat.
• Bad conductor of heat: The materials which do not easily allow heat to pass through them are called bad conductors of heat or insulators. Wood, plastics, mud, cork, cotton, ebonite, asbestos, most gases and liquids are bed conductor of heat.
• Convention of heat: Convention is a process by which heat is transferred from one part of a substance to another part through the actual movement of its constituents particles (atoms or molecules). Only liquids and gases convert heat. A solid cannot do so because solids do not flow like liquids or gases do.
• Radiation of heat: The process by which heat travels from one body to another without the intervention of any material medium is known as radiation.
  All hot objects transfer heat by radiation. Radiation does not require either a conducting medium or a convecting fluid. The sun transfers heat in all directions through the process of radiation. The radiations absorbed or emitted by a body depends upon the colour of the body.
  
• Thermos Flask (Vacuum Flask): Thermos flask is used to keep things warm and cold. It consists of a double walled glass flask, having vacuum between the walls, kept inside metallic case with the cork supporters.
  The outer and inner surfaces of the glass flask are highly silvered. The mouth of flask is fitted with air tight cork.
  
• The vacuum between the two walls of the flask prevents heat transfer by conduction or convection.
• The silver coating of the walls of the vessels reflects back heat radiations. Thus heat by radiation can neither enter inside the flask nor go out of the flask.
• The air-tight cork, which is a bad conductor of heat prevents any loss of heat by conduction or convection.
• Some heat may be transferred by conduction through thin glass walls at the neck and the poorly conducting cork.
• The total transfer of heat is very-very small, thus hot or cold liquid kept inside will keep its temperature for a long time.

Haryana State Board HBSE 7th Class Science Solutions Chapter 3 Fibre to Fabric Textbook Exercise Questions and Answers.

Haryana Board 7th Class Science Solutions Chapter 3 Fibre to Fabric

HBSE 7th Class Science Fibre to Fabric Textbook Questions and Answers

Question 1.
You must be familiar with the following nursery rhymes:
(i) Baa baa black sheep, have you any wool
(ii) Mary had a little lamb, whose fleece was white as snow
Answer the following:
(a) Which parts of the black sheep have wool?
(b) What is meant by the white fleece of the lamb?
Answer:
(a) The Hair (fleece) of the black sheep have wool.
(b) The white fleece is the v/hite hair of the lamb.

Question 2.
The silkworm is (a) a caterpiller, (b) a Larva. Choose the correct option.
(i) a
(ii) b
(iii) both a and b
(iv) neither a nor b.
Answer:
(iii) both a and b.

Question 3.
Which of the following does not yield wool?
(i) Yak
(ii) Camel
(iii) Goat
(iv) Woolly dog.
Answer:
(iv) Woolly Dog.

Question 4.
What is meant by the following terms?
(i) Reasing
(ii) Shearing
(iii) Sericulture
Answer:
(i) The fleece of the sheep alongwith a thin layer of skin is removed from its body. This process is called shearing.
(ii) Silk fibres are also animal fibres. Silkworms spin the ‘silk fibres’.
(iii) The rearing of silkworms for obtaining silk is called sericulture.

Question 5.
Given below is a sequence of steps in the processing of wool. Which are the missing steps? Add them.
Shearing, ………………. , sorting, ………………. , ………………. , ………………. , ………………. .
Answer:
Shearing, scouring, sorting, drying, dying, spinning, weaving.

Question 6.
Make sketches of the two stages in the life history of the silk moth which are directly related to the production of silk.
Answer:

(a) Female silkworm moth with eggs

Question 7.
Out of the following, which are the two terms related to silk production? Sericulture, Floriculture, Moriculture, Apiculture, Silviculture
Hints:
(i) Silk production involves cultivation of mulberry leaves and rearing silkworms.
(ii) Scientific name of mulberry is Morus alba.
Answer:
Sericulture, Moriculture.

Question 8.
Match the words of column I with those given in column II.

Answer:

Question 9.
Given below is a crossword puzzle based on this lesson. Use hints to fill in the blank spaces with letters that complete the words.

Answer:

Extended Learning-Activities And Projects

Question 1.
Paheli wants to know the maximum length of continuous silk thread that can be obtained from a cocoon.
Answer:
Do yourself. Take help to your teacher.

Question 2.
Boojho wants to know why caterpillars need to shed their skin when they grow bigger but we humans do not.
Answer:
Do yourself.

Question 3.
Boojho wants to know why caterpillars should not be collected with bare hands.
Answer:
Do yourself.

Question 4.
Paheli wanted to buy a silk frock and went to the market with her mother. There they found that the artificial (synthetic) silk was much cheaper and wanted to know why Do you know why? Find out.
Answer:
Do yourself.

Question 5.
Someone told Paheli that an animal called ‘Vicuna’ also gives wooljl Can you tell her where this animal is found? Look for this in a dictionary or an encyclopaedia.
Answer:
Do yourself.

Question 6.
When handloom and textile exhibitions are held, certain stalls display real moths of various varieties of silk and their life histories. Try and visit these stalls with elders or teachers and see these moths and stages of their life history.
Answer:
Do yourself.

Question 7.
Look for eggs of any moth or butterfly in your garden or park or any other place full of plants. They look like tiny specks (dots) laid in a cluster on the leaves. Pull out the leaves containing eggs and-place them in a cardboard box. Take some leaves of the same plant or another plant of the same variety, chop them and put them in the box. Eggs will hatch into caterpillars, which are busy eating day and night. Add leaves everyday for them to feed upon. Sometimes you may be able to collect the caterpillars. But be careful. Use a paper napkin or a paper to hold a caterpillar.
Observe everyday. Note the
(i) number of days taken for eggs to hatch
(ii) number of days taken to reach the cocoon stage and
(iii) to complete life cycle. Record your observations in your notebook.
Answer:
Do yourself.

HBSE 7th Class Science Fibre to Fabric Important Questions and Answers

Very Short Answer Type Questions

Question 1.
Name the sources of obtaining fibres.
Answer:
The sources of obtaining fibres are plants and animals.

Question 2.
Name some wool yielding animals.
Answer:
Some wool yielding animals are: sheep, angora goat, goat, yak, camel, llama, alpaca.

Question 3.
What is shearing?
Answer:
The fleece (hair) of the sheep alongwith a thin layer of skin is removed from its body. This process is called shearing.

Question 4.
From where do we get wool and silk fibres?
Answer:
Wool and silk fibres are obtained from animals. Wool is obtained from hair of animals ; as sheep hairs and silk fibtes are obtained from silk worm.

Question 5.
What is wool?
Answer:
Wool is the common name of applied to soft curly fibres obtained chiefly from the fleece of domesticated sheep.

Question 6.
What determines the fineness of wool?
Answer:
The number of crimps per centimetre determines the fineness of wool fibre.

Question 7.
Name two breeds of sheep which has finest fleece?
Answer:
Two breeds of sheep which has finest fleece are: merino and Karakul.

Question 8.
Name two systems used in the processing of wool.
Answer:
Two system used in the processing of wool are:
1. Woollen system
2. Worsted system.

Question 9.
Name two substance removed from row wool, before manufacturing yam.
Answer:
Two substance removed from raw wool, before manufacturing yarn are:
1. Yolk
2. Suint.

Question 10.
What is woolmark?
Answer:
Woolmark is the mark of standardisation given to woollen yarns and woollen products. This mark has been instituted by International Wool Secretariat (I.W.S.) located in North Yorkshire (U.K.).

Question 11.
What are the uses of wool?
Answer:
Wool is used for making fabrics, shawls, blankets, carpets, felt and upholstery.

Question 12.
Write the properties of wool fibre.
Answer:
Wool fibre is considerably resilient, has high tensile strength, light weight and is heat insulator.

Question 13.
Name the domesticated moth whose larva produces silk.
Answer:
Silk is obtained from the cocoon of the pupa of mulberry silk moth.

Question 14.
Name the plant on which silk larva feeds.
Answer:
Silk larva feeds on the leaves of mulberry tree.

Question 15.
Name the person responsible for the discovery of silk.
Answer:
Silk was discovered by Xi-Ling-Shi, the bride of Chinese emperor Huang Di, in about 3000 B.C.

Question 16.
Name the strongest variety of silk.State whether the variety you have named is wild silk or domesticated silk.
Answer:
The strongest variety of silk is “Muga”. It is the variety of wild silk.

Question 17.
Name the different varieties of processed silk.
Answer:
Organize, Gepe, Tram and Thrown Singles are different, varieties of processed silk.

Question 18.
Give uses of silk, other than for making dresses.
Answer:
Other than for making dresses, silk is used for items such as parachutes, bicycle tyres, bullet proof vests and non-absorbable sutures in surgery.

Question 19.
What is sericulture?
Answer:
The science of raising silkworms, so as to obtain silk cocoons, is called sericulture.

Question 20.
Where are sheep reared in India?
Answer:
In India sheep are reared in Sub-Himalyan region which has a cooler climate.

Question 21.
Differentiate between staple fibres and filament fibres.
Answer:
The fibres like cotton, jute, and wool are short in length. Silk however, is the longest natural fibre. The short fibres are known as the stable fibres, where as long fibres are known as the filament fibres.

Question 22.
Name some Indian breeds of sheep.
Answer:
Some Indian breeds of sheep are Lohi, Rampur bushair, Nali, Bakharwal, Marwari, and Patanwadi.

Question 23.
What is reeling of silk?
Answer:
A pile of cocoons is used for obtaining silk fibres. This process is called reeling of silk.

Short Answer Type Questions

Question 1.
Differentiate between woollen yarn and worsted yam.
Answer:
The woolen yarn is made from the woolen fibres of mixed lenghts. These fibres are, carded and spun to form a woolen yarn. The articles made from this yarn do not have smooth finished surface.

In the worsted yarn, only the long fibres are used. They are formed into smooth compact strands and are then spun to form woolen yarn. The articles made from these have smooth finished surface.

Question 2.
What do you mean by the term ‘weighting of sillf’?
Answer:
Silk when unwound from the cocoon is covered with a sticky substance. This has to be removed by washing process. As a result, silk loses about 20% of its weight. To make up for this loss some manufactures dip silk in metallic salt solution. This is known as weighting of the silk. This silk is weaker than pure silk. It than not be cleaned properly. This silk is of substandard quality and hence, deceives the buyers.

Question 3.
What is raw silk? How is it produced?
Answer:
After brushing, filaments from four to eight cocoons are joined and twisted. They are then combined with a number of other similarly twisted filaments, to make a thread that is wound on a reel. The thread is called raw silk.

It usually consists of 48 individual silk fibres. When each cocoon is unwound, it is replaced by another cocoon.Unlike the threads spun from other natural fibres, such as cotton or wool, the silk thread is made of extremely long fibres.

Question 4.
Name and describe any two types of silk threads used in the making of silk cloth.
Answer:
Two types of silk threads used in the making of silk cloth are:
1. Organzine:
Organzine thread is made by giving raw silk thread a preliminary twist in one direction and then twisting two or more of these threads in the opposite direction at rate of about 4 turns / cm.
2. Crepe: Crepe is similar to organzine, but it twisted to much greater extent, usually, 16 to 32 turns / cm.

Question 5.
Why do the wool fibres have greater bulk as compared to other fibres?
Answer:
The scales and crimps in the wool fibre make it possible to spin and felt the fleece. They help the individual wool fibres “grab” each other so that they stay together. Because of the crimp, wool fabrics have a greater bulk; than other textiles. They can retain lot of air and hence wool fabrics are good insulators of heat. The heat insulation also works boths ways.

Question 6.
Name the some breeds of sheep reared in our country. Also, indicate the quality and texture of the fibres obtained from them.
Answer:
Some Indian breeds of sheep:
Answer:

Question 7.
Write short note on ‘wool production’.
Answer:
Australia is the world’s largest producer of raw wool and contributes 29% of total world supply. Other leading producers of wool are former Soviet Republics, New Zealand, China, Argentina, South Africa and Uruguay. In India sheep are reared in Sub-Himalayan regions which has a cooler climate. The sheep which are reared in Rajasthan have poor quality of wool and are mainly reared for meat.

Long Answer Type Questions

Question 1.
What is raw silk? How is it produced?
Answer:
After brushing, filaments from four to eight cocoons are joined and twisted. They are then combined with a number of other similarly twisted filaments, to make a thread that is wound oft a reel. The thread is called raw silk. It usually consists of 48 individual silk fibres. When each cocoon is unwound, it is replaced by another cocoon. Unlike the threads spun from other natural fibres, such as cotton or wool, the silk thread is made of extremely long fibres. About 5,500 cocoons are required to produced 1 kg of raw silk.

Question 2.
What is sericulture? Explain in brief.
Answer:
The silk is obtained from cocoon. When the complete cocoon is formed, they are collected. The pupa inside the cocoon is killed by treating the cocoons with boiling water. This hot water not only kills the cocoons but also dissolves the sticky substance that holds the cocoon filaments in place. The cocoons are, thereafter, dried and brushed. This removes the outer portion that is made of coarse filaments.

The thread is then unwound from the cocoons and is wound on a reel. The thread is called the raw silk. It generally consists of 48 individual silk fibres. The silk filaments are unwound from cocoon in a manufacturing plant known as filature. The silk thread is made up of extremely long fibres. About 5,500 silkworms are needed to produce 1 kg of raw silk. The breeding and management of silk moths for producing silk is known as sericulture.

Question 3.
Explain briefly the process of wool manufacturing.
Answer:
In order to make different articles, the raw wool is processed which starts with sorting of the fibres. The fibres are sorted on the basis of length, fineness, etc. The sorting is followed by cleaning 6f the fibres. Using a suitable detergent, the fibres are cleaned from lanolin (an oily substance) and suint (the dried perspiration of sheep). The cleaned wool fibres are then dried and disentangled. Thereafter, they are drawn into a straight continuous thread. This process is called cerding. The kind of yarns that are produced may be woollen yarn or worsted yarn.

For the production oi wooiien yarn, the web is split into fine thin strands, by a process called roving. It is then spun into woollen yarn. Woollen fabric such as tweed is woven from woollen yarn. It is a bulky fabric in which short woollen fibres are arranged randomly. It does not have smooth surface.

For the production of worsted yam, the web is processed by the machines that (i) straighten the fibres (ii) make them parallel (iii) remove all the short fibres. The resultant woolen strand is then condensed by passing it through several machines, until a very thin strand of worsted roving is obtained. It is then spun to a smooth yarn.

Question 4.
What are the uses of wool? What is woolmark?
Answer:
Wool is used for making fabrics, shawls, blankets, carpets, felt (compressed wool) and upholstery. Wool felt is used to cover piano hammers. It is also used to absorb noise in heavy machinery and stereo speakers.

Shoddy is made from the used wool. To make shoddy, the existing wool fabric is cut into small pieces and then carddd. The carded wool is then respun into yarn. Such a yarn is inferior to the fresh wool and is used for making cheap woollen garments and blankets.

Woolmark:
Wool is marketed worldwide by the International Wool Secretariat (IWS), which is based in Ilkley, North Yorkshise (U.K.). The “Woolmark” instituted by IWS indicates that garments bearing this sign are made from pure new wool, that has not been used previously in any process.

Fibre to Fabric Class 7  HBSE Notes

• Wool comes from sheep, goat, yak and some other animals. These wool- yielding animals bear hair (fleece) on their body.
• The hairy skin of the sheep has two types of fibres that form its fleece : (i) the coarse beard hair, and (ii) the fine soft under hair close to the skin.
• The wool which is used for knitting sweaters or for weaving shawls is the finished product of a long process.
• Sheep hair is sheared off from the body, scoured, sorted, dried, dyed, spun and woven to yield wool.
• The hairs of camel, llama and alpaca are also processed to yield wool.
• The wool may be classified as Virgin, Hogg or pulled depending upon its quality.
• In wool production, Australia and New Zealand produce two-thirds of the world’s supply.
• Woolmark is the mark of standardisation given to pure and new wool.
• Silk fibres are also animal fibres. Silkworms spin the ‘silk fibres’. The rearing of silkworms for obtaining silk is called sericulture.
• The female silk moth lays eggs, from which hatch larvae which are called caterpillars or silkworms.
• During their life cycle, the worms spin cocoons of silk fibres.
• Silk fibres are made of a protein.
• Tassar silk, mooga silk, kosa silk, etc., are obtained from cocoons spun by different types of moths.
• The most common silk moth is the mulberry silk moth. The silk fibre from the cocoon of this moth is soft, lustrous and elastic and can be dyed in beautiful colours.
• Sericulture is a very old occupation in India. India produces plenty of silk on a commercial scale.
• A pile of cocoons is used for obtaining silk fibres. This process is called reeling of silk. The cocoons are kept under the sun or boiled or exposed to steam. The silk fibres separate out. The process of taking out threads from the cocoon for use as silk is called reeling the silk.