Class 8

Haryana Board HBSE 8th Class Maths Solutions

HBSE 8th Class Maths Solutions in English Medium

HBSE 8th Class Maths Chapter 1 Rational Numbers

• Chapter 1 Rational Numbers InText Questions
• Chapter 1 Rational Numbers Ex 1.1
• Chapter 1 Rational Numbers Ex 1.2

HBSE 8th Class Maths Chapter 2 Linear Equations in One Variable

• Chapter 2 Linear Equations in One Variable Ex 2.1
• Chapter 2 Linear Equations in One Variable Ex 2.2
• Chapter 2 Linear Equations in One Variable Ex 2.3
• Chapter 2 Linear Equations in One Variable Ex 2.4
• Chapter 2 Linear Equations in One Variable Ex 2.5
• Chapter 2 Linear Equations in One Variable Ex 2.6

HBSE 8th Class Maths Chapter 3 Understanding Quadrilaterals

• Chapter 3 Understanding Quadrilaterals InText Questions
• Chapter 3 Understanding Quadrilaterals Ex 3.1
• Chapter 3 Understanding Quadrilaterals Ex 3.2
• Chapter 3 Understanding Quadrilaterals Ex 3.3
• Chapter 3 Understanding Quadrilaterals Ex 3.4

HBSE 8th Class Maths Chapter 4 Practical Geometry

• Chapter 4 Practical Geometry InText Questions
• Chapter 4 Practical Geometry Ex 4.1
• Chapter 4 Practical Geometry Ex 4.2
• Chapter 4 Practical Geometry Ex 4.3
• Chapter 4 Practical Geometry Ex 4.4
• Chapter 4 Practical Geometry Ex 4.5

HBSE 8th Class Maths Chapter 5 Data Handling

• Chapter 5 Data Handling InText Questions
• Chapter 5 Data Handling Ex 5.1
• Chapter 5 Data Handling Ex 5.2
• Chapter 5 Data Handling Ex 5.3

HBSE 8th Class Maths Chapter 6 Square and Square Roots

• Chapter 6 Square and Square Roots InText Questions
• Chapter 6 Square and Square Roots Ex 6.1
• Chapter 6 Square and Square Roots Ex 6.2
• Chapter 6 Square and Square Roots Ex 6.3
• Chapter 6 Square and Square Roots Ex 6.4

HBSE 8th Class Maths Chapter 7 Cube and Cube Roots

• Chapter 7 Cube and Cube Roots InText Questions
• Chapter 7 Cube and Cube Roots Ex 7.1
• Chapter 7 Cube and Cube Roots Ex 7.2

HBSE 8th Class Maths Chapter 8 Comparing Quantities

• Chapter 8 Comparing Quantities InText Questions
• Chapter 8 Comparing Quantities Ex 8.1
• Chapter 8 Comparing Quantities Ex 8.2
• Chapter 8 Comparing Quantities Ex 8.3

HBSE 8th Class Maths Chapter 9 Algebraic Expressions and Identities

• Chapter 9 Algebraic Expressions and Identities InText Questions
• Chapter 9 Algebraic Expressions and Identities Ex 9.1
• Chapter 9 Algebraic Expressions and Identities Ex 9.2
• Chapter 9 Algebraic Expressions and Identities Ex 9.3
• Chapter 9 Algebraic Expressions and Identities Ex 9.4
• Chapter 9 Algebraic Expressions and Identities Ex 9.5

HBSE 8th Class Maths Chapter 10 Visualizing Solid Shapes

• Chapter 10 Visualizing Solid Shapes InText Questions
• Chapter 10 Visualizing Solid Shapes Ex 10.1
• Chapter 10 Visualizing Solid Shapes Ex 10.2
• Chapter 10 Visualizing Solid Shapes Ex 10.3

HBSE 8th Class Maths Chapter 11 Mensuration

• Chapter 11 Mensuration InText Questions
• Chapter 11 Mensuration Ex 11.1
• Chapter 11 Mensuration Ex 11.2
• Chapter 11 Mensuration Ex 11.3
• Chapter 11 Mensuration Ex 11.4

HBSE 8th Class Maths Chapter 12 Exponents and Powers

• Chapter 12 Exponents and Powers InText Questions
• Chapter 12 Exponents and Powers Ex 12.1
• Chapter 12 Exponents and Powers Ex 12.2

HBSE 8th Class Maths Chapter 13 Direct and Inverse Proportions

• Chapter 13 Direct and Inverse Proportions InText Questions
• Chapter 13 Direct and Inverse Proportions Ex 13.1
• Chapter 13 Direct and Inverse Proportions Ex 13.2

HBSE 8th Class Maths Chapter 14 Factorization

• Chapter 14 Factorization InText Questions
• Chapter 14 Factorization Ex 14.1
• Chapter 14 Factorization Ex 14.2
• Chapter 14 Factorization Ex 14.3
• Chapter 14 Factorization Ex 14.4

HBSE 8th Class Maths Chapter 15 Introduction to Graphs

• Chapter 15 Introduction to Graphs InText Questions
• Chapter 15 Introduction to Graphs Ex 15.1
• Chapter 15 Introduction to Graphs Ex 15.2
• Chapter 15 Introduction to Graphs Ex 15.3

HBSE 8th Class Maths Chapter 16 Playing with Numbers

• Chapter 16 Playing with Numbers InText Questions
• Chapter 16 Playing with Numbers Ex 16.1
• Chapter 16 Playing with Numbers Ex 16.2

HBSE 8th Class Maths Solutions in Hindi Medium

HBSE 8th Class Maths Chapter 1 परिमेय संख्याएँ

• Chapter 1 परिमेय संख्याएँ InText Questions
• Chapter 1 परिमेय संख्याएँ Ex 1.1
• Chapter 1 परिमेय संख्याएँ Ex 1.2

HBSE 8th Class Maths Chapter 2 एक चर वाले रैखिक समीकरण

• Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.1
• Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.2
• Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.3
• Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.4
• Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.5
• Chapter 2 एक चर वाले रैखिक समीकरण Ex 2.6

HBSE 8th Class Maths Chapter 3 चतुर्भुजों को समझना

• Chapter 3 चतुर्भुजों को समझना Intext Questions
• Chapter 3 चतुर्भुजों को समझना Ex 3.1
• Chapter 3 चतुर्भुजों को समझना Ex 3.2
• Chapter 3 चतुर्भुजों को समझना Ex 3.3
• Chapter 3 चतुर्भुजों को समझना Ex 3.4

HBSE 8th Class Maths Chapter 4 प्रायोगिक ज्यामिती

• Chapter 4 प्रायोगिक ज्यामिती Intext Questions
• Chapter 4 प्रायोगिक ज्यामिती Ex 4.1
• Chapter 4 प्रायोगिक ज्यामिती Ex 4.2
• Chapter 4 प्रायोगिक ज्यामिती Ex 4.3
• Chapter 4 प्रायोगिक ज्यामिती Ex 4.4
• Chapter 4 प्रायोगिक ज्यामिती Ex 4.5

HBSE 8th Class Maths Chapter 5 आँकड़ो का प्रबंधन

• Chapter 5 आँकड़ो का प्रबंधन Intext Questions
• Chapter 5 आँकड़ो का प्रबंधन Ex 5.1
• Chapter 5 आँकड़ो का प्रबंधन Ex 5.2
• Chapter 5 आँकड़ो का प्रबंधन Ex 5.3

HBSE 8th Class Maths Chapter 6 वर्ग और वर्गमूल

• Chapter 6 वर्ग और वर्गमूल Intext Questions
• Chapter 6 वर्ग और वर्गमूल Ex 6.1
• Chapter 6 वर्ग और वर्गमूल Ex 6.2
• Chapter 6 वर्ग और वर्गमूल Ex 6.3
• Chapter 6 वर्ग और वर्गमूल Ex 6.4

HBSE 8th Class Maths Chapter 7 घन और घनमूल

• Chapter 7 घन और घनमूल Intext Questions
• Chapter 7 घन और घनमूल Ex 7.1
• Chapter 7 घन और घनमूल Ex 7.2

HBSE 8th Class Maths Chapter 8 राशियों की तुलना

• Chapter 8 राशियों की तुलना Intext Questions
• Chapter 8 राशियों की तुलना Ex 8.1
• Chapter 8 राशियों की तुलना Ex 8.2
• Chapter 8 राशियों की तुलना Ex 8.3

HBSE 8th Class Maths Chapter 9 बीजीय व्यंजक एवं सर्वसमिकाएँ

• Chapter 9 बीजीय व्यंजक एवं सर्वसमिकाएँ Intext Questions
• Chapter 9 बीजीय व्यंजक एवं सर्वसमिकाएँ Ex 9.1
• Chapter 9 बीजीय व्यंजक एवं सर्वसमिकाएँ Ex 9.2
• Chapter 9 बीजीय व्यंजक एवं सर्वसमिकाएँ Ex 9.3
• Chapter 9 बीजीय व्यंजक एवं सर्वसमिकाएँ Ex 9.4
• Chapter 9 बीजीय व्यंजक एवं सर्वसमिकाएँ Ex 9.5

HBSE 8th Class Maths Chapter 10 ठोस आकारों का चित्रण

• Chapter 10 ठोस आकारों का चित्रण Intext Questions
• Chapter 10 ठोस आकारों का चित्रण Ex 10.1
• Chapter 10 ठोस आकारों का चित्रण Ex 10.2
• Chapter 10 ठोस आकारों का चित्रण Ex 10.3

HBSE 8th Class Maths Chapter 11 क्षेत्रमिति

• Chapter 11 क्षेत्रमिति Intext Questions
• Chapter 11 क्षेत्रमिति Ex 11.1
• Chapter 11 क्षेत्रमिति Ex 11.2
• Chapter 11 क्षेत्रमिति Ex 11.3
• Chapter 11 क्षेत्रमिति Ex 11.4

HBSE 8th Class Maths Chapter 12 घातांक और घात

• Chapter 12 घातांक और घात Intext Questions
• Chapter 12 घातांक और घात Ex 12.1
• Chapter 12 घातांक और घात Ex 12.2

HBSE 8th Class Maths Chapter 13 सीधा और प्रतिलोम समानुपात

• Chapter 13 सीधा और प्रतिलोम समानुपात Intext Questions
• Chapter 13 सीधा और प्रतिलोम समानुपात Ex 13.1
• Chapter 13 सीधा और प्रतिलोम समानुपात Ex 13.2

HBSE 8th Class Maths Chapter 14 गुणनखंडन

• Chapter 14 गुणनखंडन Intext Questions
• Chapter 14 गुणनखंडन Ex 14.1
• Chapter 14 गुणनखंडन Ex 14.2
• Chapter 14 गुणनखंडन Ex 14.3
• Chapter 14 गुणनखंडन Ex 14.4

HBSE 8th Class Maths Chapter 15 आलेखों से परिचय

• Chapter 15 आलेखों से परिचय Intext Questions
• Chapter 15 आलेखों से परिचय Ex 15.1
• Chapter 15 आलेखों से परिचय Ex 15.2
• Chapter 15 आलेखों से परिचय Ex 15.3

HBSE 8th Class Maths Chapter 16 संख्याओं के साथ खेलना

• Chapter 16 संख्याओं के साथ खेलना Intext Questions
• Chapter 16 संख्याओं के साथ खेलना Ex 16.1
• Chapter 16 संख्याओं के साथ खेलना Ex 16.2

Haryana State Board HBSE 8th Class Science Solutions Chapter 10 Reaching the Age of Adolescence Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 10 Reaching the Age of Adolescence

HBSE 8th Class Science Reaching the Age of Adolescence Textbook Questions and Answers

Question 1.
What is the term used for secretions of endocrine glands responsible for changes taking place in the body?
Answer:
Hormones.

Question 2.
Define adolescence.
Answer:
Adolescence: The period of life, when the body undergoes changes, leading to reproductive maturity is called adolescence.

Question 3.
What is menstruation? Explain.
Answer:
When egg produced by ovary does not get fertilized, it along with the thickened lining of the uterus and blood vessels get flown off out of the body every month as bleeding in women. This is called menstruation.

Question 4.
List the changes in the body that take place at puberty.
Answer:
Certain changes take place in the bodies of boys and girls at age of puberty. These include:
(i) Growing of hair at different body parts
(ii) Sudden increase in height.
(iii) Growth of moustaches and beards in boys.
(iv) Voice,of boys get coarsed.
(v) Development of breast in girls and hips get heavy.
(vi) Development of sex organs.

Question 5.
Prepare a table having two columns depicting names of endocrine glands and hormones secreted by them.
Answer:

Question 6.
What are sex hormones? Why are they named so? State their function.
Answer:
Hormones which constitute the secondary sexual characters are called sex hormones. They are called sex hormones because it is because of them that sex is diferentiated i.e. a boy is distinguished from a girl due to these hormones. Their function is to develop the secondary sexual characters in boys and girls.

Question 7.
Choose the correct option:
(a) Adolescents should be careful about what they eat, because ………….
(i) proper diet develops their brains.
(ii) proper diet is needed for the rapid growth taking place in their body.
(iii) adolescents feel hungry all the time.
(iv) taste buds are well developed in teenagers.
Answer:
(ii) proper diet is needed for the rapid growth taking place in their body.

(b) Reproductive age in women starts when their …………..
(i) menstruation starts.
(ii) breasts start developing.
(iii) body weight increases.
(iv) height increases.
Answer:
(i) menstruation starts.

(c) The right meal for adolescents consists of …………
(i) chips, noodles, coke.
(ii) chapati, dal, vegetables.
(iii) rice, noodles and burger.
(iv) vegetable cutlets, chips and lemon drink.
Answer:
(ii) chapati, dal, vegetables.

Question 8.
Write notes on:
(a) Adam’s apple.
(b) Secondary sexual characters.
(c) Sex determination in the unborn baby.
Answer:
(a) Adam’s Apple:
Adam’s apple is a protruding part in the throat. It is the enlarged voice box or larynx, which gets enlarged at the onset of puberty. This makes the voice of the boys hoarse.

(b) Secondary Sexual Characters are the characters which distinguish a boy from a girl. Characters like hair on chest, under the arms, development of breast, beard and moustaches etc. are all called secondary sexual characters.

(c) Sex determination in unborn baby: The sex of the unborn baby is determined by the sex chromosomes of the father. An unfertilized
egg always have X chromosome. If a sperm contributes X chromosome then the baby will be a female and if the sperm contributes Y chromosome, the baby will be a male. So it is the father, who is responsible for the sex of the unbomhaby.

Question 9.
Word game: Use the clues to work out the words.
Across
3. Protruding voice box in boys
4. Glands without ducts
7. Endocrine gland attached to brain
8. Secretion of endocrine glands
9. Pancreatic hormone 10. Female hormone

Down
1. Male hormone
2. Secretes thyroxine
3. Another term for Teenage
5. Hormone reaches here through blood stream
6. Voice box
7. Term for changes at adolescence

Answer:

Question 10.
The table below shows the data on likely heights of boys and girls as they grow in age. Draw graphs height and age for both boys and girls on the same graph paper. What conclusions can be drawn from these graphs?

Answer:
We conclude that girl are taller than boys age of 12 yr. generally and there height is same at the age of 16 years but some boys gain height and generally become taller then girls.

Extended Learning – Activities And Projects

1. Find out from your elder relatives about their awareness of the leagal status of early marriage. You yourself may get information on it from your teacher, parents, a doctor or the internet. Write a two-minute speech explaining why early marriage is not good for the couple.
Answer:
The legal marriagable age for girls is 18 years and for boys it is 21 years. Before this age marriage is considered a crime. Early marriage is not good for couples because they are not prepared physically and mentally for the responsibilities of married life. A girl attains sexual maturity at age of about eighteen years. Before that her resproductive system is not fully prepared to bear a baby. Similarly boys are not capable of running the household as most of the boys at this age are pursuing their studies. So, the boys and girls should attain physical and mental maturity before getting married.

2. Collect newspaper cuttings and information in magazines about HIV/AIDS. Write a one page article of 15 to 20 sentences on HIV/AIDS.
Answer:
HIV/AIDS is a sexually transmitted diseased (STD) that means this diseases mostly spreads by sexual contacts with an HIV/AIDS infected persons. AIDS stands for Acquired Immunodeficiency Syndrome. It is created by HIV virus. This disease is a fatal disease for which no permanent treatement has been deviced by the scientists. AIDS is actually a disease which destroys the patients immune system slowly. The damage is most of the time permanent and beyond repair. Due to weak immunity the patient easily fall prey to many diseases which eventually kill the person.

Prevention is the only cure for HIV/AIDS. It is advised that one should maintain sexual hygiene and practice safe sexual relationship with a single partner.

3. In our country, according to a census, there are 882 adolescent femals for every 1000 males. Find out:
(a) the concerns of the community regarding this low ratio. Remember that the chance of having a boy or a girl is equal.
(b) what amniocentesis is and how useful this technique is. Why, is its use for indentification of sex of the unborn child banned in India l
Answer:
(a) The society is quite concerned about this issue. This is going to create a problem for them in future as it will become difficult for the boys to find girls for marriage.

(b) It is used to see, if all the organs of a feotus are developing well. It is banned in India to use this technique to determine the sex of the unborn child because they kill the female feotus to have baby boys in future. This is called female feoticide. The female feoticide has disturbed the ratio of boys and girls in India.

4. Put your ideas together and write a short note on the importance of knowing facts about reproduction.
For more information , visit:

• www.teenshealth.org/teen/sexual_health/
• www.ama_assn.org/ama/pub/category/ 1947.html
• www.adolescenthealth.com

Answer:
It is important to know facts about reproduction, because this phase i.e. reproduction phase has to come in every bodies life. It will help to handle all the physical and mental changes coming with sexual maturity in the bodies. It will also help in deciding one’s own course of life in future and save for many STDs.

HBSE 8th Class Science Reaching the Age of Adolescence Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is the phase of life when the body undergoes changes to attain reproductive maturity called?
Answer:
Adolescence.

Question 2.
What is the age period of adolescence?
Answer:
13 years to 18 years.

Question 3.
What is reproductive maturity called?
Answer:
Puberty.

Question 4.
Write any two changes in bodies of boys during adolescence.
Answer:
Increase in height, hairy line above lips.

Question 5.
What makes a person tall during adolescence?
Answer:
Elongated long bones of arms and legs.

Question 6.
What happens to voice box at puberty?
Answer:
It begins to grow.

Question 7.
What is the protruding part of the larynx visible in boy’s throat called?
Answer:
Adam’s Apple.

Question 8.
What changes occur in the voice of boy’s at the onset of puberty?
Answer:
It becomes hoarse.

Question 9.
Why do growing boys and girls get acnes or pimples?
Answer:
Due to increased secretions of sebacious glands.

Question 10.
What are those characters called, which distinguish a boy from a girl?
Answer:
Secondary sexual characters.

Question 11.
Give any one secondary sexual character of boys.
Answer:
Growth of moustaches and beard.

Question 12.
Give any one secondary sexual character of girls.
Answer:
Growth of breasts.

Question 13.
What controls the body changes during adolescence?
Answer:
Hormones.

Question 14.
What are hormones?
Answer:
Hormones are the chemical substances secreted by Endocrine glands.

Question 15.
Name the hormones secreted by testes.
Answer:
Testosterone.

Question 16.
Which hormone is secreted by ovaries 7
Answer:
Estrogen.

Question 17.
Which endocrine gland is called the master gland?
Answer:
Pituitary gland.

Question 18.
What are hormones secreted by testes and ovaries called collectively?
Answer:
Sex hormones.

Question 19.
Name the sex hormones secreted by testes and ovaries.
Answer:
Testosterone and Estrogen.

Question 20.
Name any one hormone secreted by Pituitary gland.
Answer:
Follicle stimulating Hormone or FSH.

Question 21.
Which hormone is responsible for the maturity of ova or sperms?
Answer:
Follicle stimulating hormone.

Question 22.
What is the common name given to ova and sperms?
Answer:
Gametes.

Question 23.
What is the beginning of menstruation called?
Answer:
Menarche.

Question 24.
What is the stoppage of menstruation called?
Answer:
Menopause.

Question 25.
What are the names given to sex chromosomes?
Answer:
X and Y.

Question 26.
Which sex chromosome determines the sex of body?
Answer:
Y Chromosome.

Question 27.
Which hormone is secreted by thyroid?
Answer:
Thyroxin.

Question 28.
Which hormone is secreted by pancreas?
Answer:
Insulin.

Question 29.
Which hormone controls the blood sugar level?
Answer:
Insulin.

Question 30.
Which hormone is secreted by Adrenal glands?
Answer:
Adrenalin.

Question 31.
Which hormone is called stress hormone?
Answer:
Adrenalin.

Question 32.
Why adrenalin is called stress hormone?
Answer:
Adrenalin is called stress hormone because it helps to calm down when one is angry.

Question 33.
What is a balanced diet?
Answer:
Diet containing all the necessary minerals in right proportion is called a balanced diet.

Question 34.
Name any food, which is called a balanced food in itself.
Answer:
Milk.

Question 35.
Which virus causes AIDS?
Answer:
HIV.

Short Answer Type Questions

Question 1.
What is adolescence?
Answer:
The phase of a person’s life, when his body undergoes changes to attain reproductive maturity is called adolescence. Adolescence begins at the age of 13 and lasts till the age of 18 or 19 years.

Question 2.
What are the signs of adolescence?
Answer:
Certain body changes mark the onset of puberty. Hairy line above lips in boys and sudden increase in height are the signs of puberty. In girls developing breasts show the on set of puberty.

Question 3.
Why some boys or girls have improportionate body parts during adolescence 7
Answer:
Some times the boys and girls have improportionate body parts. They look tall but face look smaller or other tilings. This is because all body parts do not grow at the same rate. But slowly they all catch up and body becomes balanced.

Question 4.
What changes take place in the body of adolescents during this period?
Answer:
Many changes take place in the bodies of boys and girls during adolescence. Their shoulders become wider and chest becomes broader. Girls get developed breasts and their hips become wider. Muscles of boys grow more than the girls.

Question 5.
What changes occur in the voice of boys and girls during puberty?
Answer:
The voice box or the larynx begins to grow. Boys have more grown voice box. It can be seen as the protrubed part in their throat.
Their voice becomes deep and sometimes, it grows more than controlled limit and their voice become hoarse. Girls get a high pitched voice.

Question 6.
What causes the changes in human body during puberty?
Answer:
The changes which occur during puberty are caused due to some chemical substances secreted by glands. These chemical substances are acalled Hormones. Endocrine system in human body has various glands, which secrete many important hormones which help the body to grow and mature.

Question 7.
How do sex hormones work in human body?
Answer:
In males the testosterone is secreted by testes and it causes growth of moustaches and beard. In girls estrogefi causes the development of mammary glands . They develop inside the breast and cause enlargement of breasts.

Question 8.
How does pituitary gland initiate the puberty in humans?
Answer:
Pituitary gland is called the master gland. It stimulates the testes and ovaries to produce sex hormones i.e. Testosterone and estrogen. These sex hormones further initiate the changes in body to attain sexual maturity.

Question 9.
What is menstruation?
Answer:
Monthly bleeding in women is called menstruation, when egg is matured and released by ovaries. It if not fertilized is dispelled by body along with the thick lining of uterus and with blood vessels. It is released from the body in form of monthly bleeding. It is called menstruation.

Question 10.
How the sex of the body is determined?
Answer:
Every human beings have 23 pairs of chromosomes in the nuclei of their cells. A pair of sex hormones are also among them. Females have XX sex chromosomes and males have XY sex chromosomes, when after fertilization the zygote get both X chromosomes from male and female, it will develop into a baby girl. When the zygote get X chromosome from female and Y from male, then it develops into a male. Thus the chromosome from a male decides if a baby will be a male or a female.

Long Answer Type Questions

Question 1.
What changes occur in body during puberty?
Answer:
Various changes occur in the body of human beings during puberty. These changes occur due to hormones secreted by reproductive organs. These changes are the following:
(a) Physical changes:
Various changes occur in the bodies of boys and girls. Boys get broader shoulders and wider chest. Sudden increase in their height is accompanied by growth of hair on their body parts. They get moustaches and beard.Girls get developed breasts and wider hips. More secretions from sweat and oil glands cause pimples and acnes in some young people.

(b) Change in Voice:
Voice of boys become deep due to enlarged larynx. Some time more growth in voice box is visible as Adam’s Apple in their throats. Their voice becomes even coarse in case of extra growth of larynx. Voice of girls become high pitched.

(c) Development of Sex Organs:
The reproductive organs of boys and girls become active. Testes start producing sperms and ovaries release matured eggs. Mental and Emotional Maturity: Young people become more mature mentally, emotionally and intellectually.

Question 2.
How are the changes of adolesence controlled by hormones?
Answer:
The endocrine system of body secretes many chemical substances which are directly poured into the blood stream, these chemical substances are called hormones. All changes taking place during adolescence are controlled by these hormones.

Pituitary glands secrete growth hormones which stimulates the sex organs to release hormones.. Testes start secreting testosterone and ovaries start secreting estrogen. These sex hormones cause secondary sexual characters. Estrogen causes development of mammary glands which develop under breast, thus breast starts enlarging in females.

Question 3.
How can bad habits like Drug addiction harm the young people?
Answer:
Boys and girls feel a little bit insecure and confused during adolescence due to sudden changes in their bodies. This can mislead them to certain unhealthy and immoral habbits, like drug addiction and many others. Drug addiction is a very bad habit which can spoil our lives. It is easy to start, taking drugs but very difficult to shun this habit. Drugs can cause many long term harms on our bodies.

They make our body weak and prone to many communicable diseases like AIDS and many other sexual disorders. AIDS virus HIV can pass on to a healthy person from an infected person by sharing the infected syringe. The drug addicts inject drugs by using syringe. The same syringe is shared by other addicts also, so the infected syringe can spread AIDS to others also.

Question 4.
Who is responsible to determine the sex of unborn baby: Father or mother?
Answer:
Each human being have 23 pairs of chromosomes in the nuclei of every cell. These chromosomes contain the hereditary information. Out of these chromosomes a pair of chromosome are called sex chromosomes, which are named X and Y Chromosomes. Each female has 2 X chromosomes while the males have one X chromosome and one Y chromosome. The unfertilized egg released by ovaries always have one X chromosome. Testes produce some sperms with X chromosome and some with Y chromosome.

If sperms with X chromosome fertilize with egg with unborn is a female, but if the sperms with Y chromosome fertilizes with egg, then the unborn baby will be a male. So, it becomes clear that it is the sperm released by father carrying X or Y chromosomes, that determines the sex of the unborn baby.

Question 5.
What should be done to maintain reproductive health?
Answer:
Following measures can help the young people to maintain their reproductive health.
(i) Balanced Diet:
Diet is very important for a growing body. Diet should be a balanced diet. Balanced diet contains all the necessary elements in required proportion. Elements like carbohydrates, proteins, fats and vitamins should be integral part of a balanced diet. Milk provides all the required elements in required proportion. Junk and fast food are good to taste but they are not nutritious so they should not be included in diet.

(b) Personal Hygiene:
One should keep one’s body clean by bathing everyday. All parts of the body should be washed properly because infections can take place due to more sweat and oil secretion by sweat and oil glands.

(c) Physical Exercise:
Daily routine of physical exercise can keep body fit and circulation of blood gets maintained providing energy to all parts of the body.

Reaching the Age of Adolescence Class 8 HBSE Notes

1. A baby becomes adult after passing a few development stages.
2. The age at which a child becomes capable of reproduction is called adolescence.
3. At the age of 11 years to 19 years a child reaches puberty.
4. Reproductive organs start developing as the puberty sets in.
5. Various changes occur in the bodies of boys and girls at age of puberty. Hair starts growing at different parts of body. Girls have developed breasts, heavy hips, boys get.moustaches and beard, their voice become heavy.
6. Height gain is prominent at age of puberty along with other changes. Hormones starts taking control of the reproductive organs, and make the beginning of maturity of reproductive organs.
7. Hormones are the chemical substances which are secreted by the pituitary glands directly into the blood stream.
8. Growth hormones stimulate other glands to secrete various other hormones to control various other body functions.
9. Various hormones secreted by different glands perform various functions. Ovaries and testes secrete hormones for sexual maturity, pancreas secrete Insulin to control sugar level, thyroid secret thyroxin and adrenal glands produce adrenalin. All these hormones are necessary for proper growth and development of body.
11. With onset of puberty females have hormones like estrogen. They have their uterine wall prepared to receive the fertilized egg. They have another phenomenon called menstruation. In this phenomenon they get the unfertilized egg flown out of body through blood.
12. Reproductive health needs a lot of care and one needs to maintain hygiene and physical activity.
13. Proper nutrition and balanced diet in necessary for growing body, so it should be taken care of.

Haryana State Board HBSE 8th Class Science Solutions Chapter 11 Force and Pressure Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 11 Force and Pressure

HBSE 8th Class Science Force and Pressure Textbook Questions and Answers

Question 1.
Give two examples each of situations in which you push or pull to change the state of motion of objects.
Answer:
(i) We push the door to open it.
(ii) We pull the desk to change its position.

Question 2.
Give two examples of situations in which applied force causes a change in the shape of an object.
Answer:
When we apply force on clay with our fingers, its shape gets changed, when we press balloon with our hands, its shape get changed.

Question 3.
Fill in the blanks in the following statements :
(a) To draw water from a well we have to _________ at the rope.
(b) A charged body _________ an uncharged body towards it.
(c) To move a loaded trolley we have to _________ it.
(d) The north pole of a magnet _________ the north pole of another magnet.
Answer:
(a) pull
(b) attracts
(c) push it
(d) repels.

Question 4.
An archer stretches her bow while taking aim at the target. She then releases the arrow, which begins to move towards the target. Based on this information fill up the gaps in the following statements using the followiong terms:
muscular, contact, non-contact, gravity, friction, shape, attraction
(a) To stretch the bow, the archer applies a force that causes a change in its _________
(b) The force applied by the archer to stretch the bow is an example of _________ force.
(c) The type offeree responsible for a change in the state of motion of the arrow is an example of a _________ force.
(d) While the arrow moves towards its target, the forces acting on it are due to _________ and that due to _________ of air.
Answer:
(a) shape
(b) muscular
(c) contact
(d) gravity and friction.

Question 5.
In the following situations identify the agent exerting a force and the object on which it acts. State the effect of the force in each case.
(a) Squeezing a piece of lemon between the fingers to extract its juice.
(b) Taking out paste from a toothpaste tube.
(c) A load suspended from a spring while its other end is on a hook fixed to a wall.
(d) An athlete making a high jump to clear the bar at a certain height.
Answer:
(a) Agent are fingers, object is lemon, effect of force can be observable in form of lemon juice being expelled by squeezing.

(b) Agent is hand of the person squeezing the tube, object is toothpaste tube and effect of the force can be observed’ as the paste coming out of the tube.

(c) Agent is the load suspended, object is the spring and effect can be seen in the form of elongation of spring on suspension of load.

Question 6.
A blacksmith hammers a hot piece of iron while making a tool. How does the force due to hammering affect the piece of iron?
Answer:
The force due to hammering causes the change in the shape of the iron and iron can be moulded in the shape of the required tool.

Question 7.
An inflated balloon was pressed against a wall after it has been rubbed with a piece of synthetic cloth. It was found that the balloon sticks to the wall. What force might be responsible for, the attraction between the balloon and the wall?
Answer:
Electrostatic force.

Question 8.
Name the forces acting on a plastic bucket containing water held above ground level in your hand. Discuss why the forces acting on the bucket do not bring a change in its state of motion.
Answer:
Forces acting on the plastic bucket are the muscular force and gravitational force. The forces do not bring the change in its state of motion because they are acting in opposite direction with equal magnitude. The effect of the gravitational force will pull it down if the muscular force will grow weak. The body will feel the stretch of gravitational force and will have to bend” to cancel the magnitude of gravitational force.

Question 9.
A rocket has been fired upwards to launch a satellite in its orbit. Name the two forces acting on the rocket immediately after leaving the launching pad.
Answer:
Gravitational force and frictional force.

Question 10.
When we press the bulb of a dropper with its nozzle kept in water, air in the dropper is seen to escape in the form of bubbles. Once we release the pressure on the bulb, water gets filled in the dropper.
The rise of water in the dropper is due to
(a) pressure of water
(b) gravity of the earth
(c) shape of rubber bulb
(d) atmospheric pressure
Answer:
(d) atmospheric pressure.

Extended Learning – Activities and Projects

Question 1.
Make a 50 cm x 50 cm bed of dry sand about 10 cm in thickness. Make sure that its top surface is levelled. Take a wooden or a plastic stool. Cut two strips of graph paper each with a width of 1 cm. Paste them vertically on any leg of the stool-one at the bottom and the other from the top. Now gently put the stool on the sand bed with its legs resting on the and Increase the size of sand bed if required. Now put a load, say a school bag full of books, on the seat of the stool. Mark the level of sand on the graph strip. This would give you the depth, if any, to which the legs of stool sink in sand. Next, turn the stool upside down so that now it rests on its seat on the sand bed. Note the depth to which the stool sinks now. Next, put the same load on the stool and note the depth to which it sinks in the sand. Compare the pressure exerted by the stool in the two situations.
Answer:
For self attempt.

Question 2.
Take a tumbler and fill it with water. Cover the mouth of the tumbler with a thick card similar to that of a postcard Hold the tumbler with one hand while keeping the card pressed to its mouth with your other hand. Turn the tumbler upside down while keeping the card pressed to its mouth. Make sure that the tumbler is held vertical.

Gently remove the hand pressing the card. What do you observe? Does the card get detached allowing the water to spill? With a little practice you will find that the card continues to hold water in the tumbler even after it is not supported by your hand. Also try this activity by using a piece of cloth to hold the tumbler in an upside down position.
Answer:
For self attempt.

Question 3.
Take 4-5 plastic bottles of different shapes and sizes. Join them together with small pieces of glass or rubber tube as shown in Fig. Keep this arrangement on a level surface. Now pour water in any one of the bottles.

Note whether the bottle in which water is poured gets filled first or all the bottle in which water is poured gets filled first or all the bottles get filled up simultaneously. Note the level of water in all the bottles from time to time. Try to explain your observations.
For more information on force and pressure visit:
→ www.glenbrook.kl2 .il.us/gbssci/phys/class/ newtlauws/u212a,html
→ www.hatesville.kl2.in.us/physics/phyNet/ Mechanics/Newton2/Pressure .html
→ www.kids.earth.nasa.gov/archive/ air_pressure/
Answer:
For self attempt.

Activities

Activity No. 11.1

Activity No. 11.5
Studying the Effect of Force on Objects

Very Short Answer Type Questions

Question 1.
Define force.
Answer:
Any push or pull is called force.

Question 2.
When does a body move?
Answer:
A body moves when force is applied.

Question 3.
What is the first requirement to put force into play?
Answer:
Interaction between two objects.

Question 4.
Give any example of push.
Answer:
Pushing a table to wall.

Question 5.
Give an example of pull.
Answer:
Pulling the door to shut.

Question 6.
When force is applied on the object in the same direction of motion, what happens?
Answer:
The speed will increase.

Question 7.
What will happen when force is applied in the direction opposite to the movement of object?
Answer:
The speed will decrease.

Question 8.
How is the strength of a force expressed?
Answer:
In magnitude.

Question 9.
What effect does force put of state of motion?
Answer:
The speed of the object may change.

Question 10.
What is the state of motion of an object?
Answer:
The speed and direction of an object is called state of motion.

Question 11.
Does the force change the direction of the moving object?
Answer:
Yes.

Question 12.
Does the force change the shape of the object?
Answer:
Yes.

Question 13.
What is the contact force?
Answer:
Force which comes in action when objects are in contact.

Question 14.
What is the muscular force?
Answer:
Force resulting due to action of muscles.

Question 15.
Give examples of muscular force.
Answer:
Bending, moving, kicking etc.

Question 16.
What kind of force is the muscular force?
Answer:
Contact force.

Question 17.
What is friction?
Answer:
Force acting equal and opposite to the moving object is friction.

Question 18.
What kind oi force is the friction?
Answer:
Contact force.

Question 19.
Give example of friction force.
Answer:
Stopping of a rolling ball.

Question 20.
Which force stops the moving striker on a carrom board?
Answer:
Friction.

Question 21.
Why does the soal of our shoes get torn away by walking?
Answer:
Due to friction between soal and road.

Question 22.
What are non-contact forces?
Answer:
Forces acting jrom distance without forming contact.

Question 23.
What is magnetic force?
Answer:
Force exerted by a magnet is called magnetic force.

Question 24.
What happens when similar poles of magnets come in contact?
Answer:
They repel each other.

Question 25.
What happens when opposite poles of magnets come in contact?
Answer:
They attract each other.

Question 26.
What is the electrostatic force?
Answer:
Force exerted by the charged bodies is called electrostatic force.

Question 27.
When a comb rubbed against hair is brought near the small pieces of paper, the paper attaches to the comb which force has attracted papers?
Answer:
Electrostatic force.

Question 28.
What kind of forces are magnetic force and electrostatic force?
Answer:
Non-contact forces.

Short Answer Type Questions

Question 1.
How do we feel force in our daily life?
Answer:
Many big or small actions make us feel the force. We have to push or pull many objects daily. A moving ball stops on its own, the ball changes the direction of its motion, when hits with a bat. We churn curd to make lassi and many other actions.

Question 2.
What is force? Define with example.
Answer:
Force is the pull or push of the objects. Actions like pushing, pulling, bending, running, lifting etc. are the examples of force. Moving or stopping or changing shape and direction of motion of objects are the various actions showing force in play.

Question 3.
What happens when two people push an object from same direction?
Answer:
When two people push or pull something together in same direction, the force applied by them get added and the action becomes easy.

Question 4.
How can force change the state of motion?
Answer:
Force can change the state of motion by changing the direction of the motion and by changing the speed of the motion. Force in the direction of the motion increases the speed and force in opposite direction decreases the speed.

Question 5.
What is the state of motion?
Answer:
State of motion of an object is its speed and its direction. State erf zero motion means state of rest. An object can be in two positions one at rest or at motion. Any change in this position can be the change in the state of motion.

Question 6.
What is muscular force? Why is it a contact force?
Answer:
The force exerted by the action of the muscles is called muscular force. Muscular activities like running, bending, walking etc. produce muscular force. Muscular force is a contact force because it is applied only when it is in contact with an object.

Question 7.
What is force of Motion? How does it arise?
Answer:
Force of friction is force opposite and equal to the force of moving body. Force of friction arises when there is a contact between two surfaces and some movement takes place in them. Force of friction is a contact force as it only arises when two surfaces come in contact with each other.

Question 8.
Why does a moving ball gradually come to rest?
Answer:
A moving bail comes to rest on its own due to force of friction. When ball moves on the ground, their surfaces come in contact to each other. The ball and the ground exert equal and opposite force on each other, which gradually brings the moving ball to a stop.

Question 9.
What is electrostatic force? What kind of a force is it?
Answer:
Electrostatic force is exerted by a charged body on another charged or uncharged body. For this it is not necessary for the two bodies to be in contact with each other. This force is applicable from a distance so it is a non-contact force.

Question 10.
What is pressure? What is the relation of pressure with area on which it is applied?
Answer:
Force exerted on per unit area is called pressure. Pressure is related with area on which it is applied. When the area is increased the pressure exerted is less. But when the area on which pressure is exerted is decrease the pressure increases. So we conclude that pressure increases with decrease in area.

Long Answer Type Questions

Question 1.
How will you prove that pressure of liquids decrease with increase in height ^ of its column?
Answer:
For this to be proven take aplastic

container. Take a pin and make holes in the container in horizontal line from bottom to middle of the container. Now put water in the container and observe, you will see the water will come out with maximum pressure while the hole at the top will have the minimum pressure of water.

Question 2.
What changes are caused dud to application of farce on object?
Answer:
Force when applied on an object cause many changes on the object. Following changes occur due to application of force:
(i) Force change the state of motion : Force can change the state of motion of the object. It can increase or decrease the speed of the moving object. It can change the direction of the moving object.

(ii) Force can change the shape of the object: Force can change the shape of the object on which it is applied. When force is applied on some object, it always have some effect on the shape of the object. The change in the object is some time visible and some time, it is pot visible, but change in shape of the object is always accompanied by application of force.

Question 3.
What are the contact forces? Explain different forces which are contact forces.
Answer:
Contact forces are the forces which come in play when two objects come in contact with each other. Following forces are the contact forces :
(i) Muscular Force : The force which is exerted due to action of muscles is called muscular force. Actions like bending, running, moving etc. are examples of muscular forces. It is a contact force because it comes in play when it comes in contact of the object.

(ii) Friction: Equal and opposite force being exerted on an object when its surface comes in contact with other surface. It is also a contact force because it is exerted when two surfaces come in contact with each other Halting of a moving ball on its own is an example of force of friction.

Question 4.
What are the non-contact forces? Explain different non-contact forces.
Answer:
Non-contact forces are those forces, which can be exerted from a distance without establishing a contact. Following forces are the non-contact forces :
(i) Magnetic force : Force exerted by a magnet on another magnet or magnetic substance like iron is called magnetic force. Like poles of a magnet repel each other and opposite poles of a magnet attract each other.

(ii) Electrostatic Force: Force exerted by a charged body on other charged body or uncharged body is called electrostatic force. If we rub a comb with our hair and bring it near some small bits of paper, it will attract the bits of paper towards itself. This is electrostatic force which acts without making a direct contact with other charged or uncharged object.

(iii) Force of Gravity : Earth pulls every freely falling object towards its centre. This force exerted by earth is called force of gravity. This is also a non-contact force as it acts from a distance.

Force and Pressure Class 8 HBSE Notes

• Every push or pull is called force.
• Force comes into action when an object interacts with other object.
• Forces when implied in same direction add to each other, but when applied in opposite directions, they cancel each other. Equal forces applied in opposite direction results in net zero force.
• Force has magnitude and direction.
• Force can bring many changes in body on which it is applied.
• Force can change the speed of the moving body. Force in same direction of motion can increase the speed and in opposite direction can decrease the speed.
• Force can change the direction of the object in motion or at rest.
• Force can change theshapeof theobject. Force when applied on an object is always accompanied by change’in its shape.
• Two objects when come in contact with each other, they apply force on each other, this is called contact force. Muscular force, friction force etc. are examples of contact force.
• Force acting opposite to the direction of motion of a moving object is called force of friction.
• Force that acts from a distance is called a non-contact force, Magnetic force, electrostatic force and gravitational force are examples of non-contact force.
• Force exerted per unit area is called pressure.
• Liquids and gases also exert pressure in all directions.
• Pressure exerted by air is called atmospheric pressure.

Haryana State Board HBSE 8th Class Science Solutions Chapter 9 Reproduction in Animals Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 9 Reproduction in Animals

HBSE 8th Class Science Reproduction in Animals Textbook Questions and Answers

Question 1.
Explain the importance of reproduction in organisms.
Answer:
Reproduction is very important for the organisms. The organisms reproduce to produce young ones like them. It carries on their generation. If reproduction does not take place, no living being would survive on earth. Secondly, specials characters of an organism are carried over to its next generation through reproduction only.

Question 2.
Describe the process of fertilization in human beings,
Answer:
Human beings reproduce sexually. In human beings fertilization takes place internally i.e. inside female body. Males eject sperms inside females body. Sperms and ovum fuse to form the fertilized egg called zygote. During this process the nucleus of the sperm fuses with the nucleus of the ovum thus forming a single nucleus.
Thus zygote is formed with a single nucleus, this completes the process of fertilization.

Question 3.
Choose the most appropriate answer:
(a) Internal fertilisation occurs:
(i) in female body
(ii) outside female body.
(iii) in male body.
(iv) outside male body.
Answer:
(a) In female body

(b) A tadpole develops into an adult frog by the process of:
(i) fertilization
(ii) metamorphosis.
(iii) embedding
(iv) budding.
Answer:
(b) metamorphosis

(c) The number of nuclei present in a zygote is:
(i) none
(ii) one
(iii) two
(iv) four
Answer:
(c)two.

Question 4.
Indicate whether the following sentences as True (T) or False (F):
(a) Oviparous animals give birth to young ones. ( )
(b) Each sperm is a single cell. ( )
(c) External fertilisation take place in frog. ( )
(d) A new human individual developed from a cell called gamete. ( )
(e) Egg laid after fertilisation is made up of a single cell. ( )
(f) Amoeba reproduces by budding. ( )
(g) Fertilisation is necessary even in asexual reproduction. ( )
(h) Binary fission is a method of asexual reproduction. ( )
(i) A zygote is formed as a result of fertilisation. ( )
(j) An embryo is made up of a single cell.( )
Answer:
(a) False
(b) True
(c) True
(d) False
(e) True
(f) False
(g) False
(h) True
(i) True
(j) False.

Question 5.
Give two differences between a zygote and a foetus?
Answer:
(i) Zygote is made up of a single cell while foetus is made up of many cells.
(ii) Zygote does not have well developed limbs, foetus has well developed and identifiable limbs.
(iii) Zygote is formed by the fertilization of sperms and ovum, foetus is formed by the repeated divisions of the zygote .

Question 6.
Define asexual reproduction. Describe the two methods of asexual reproduction in animals.
Answer:
Asexual reproduction is that type of reproduction in which only single parent is involved. Asexual reproduction takes place by different methods like budding, binary fission etc. Let us discuss these two methods:
(i) Budding:
This type of reproduction takes place in Hydra and Bacteria. A part of the organism starts bulging out. Slowly it grows and develops into a separate individual.

(ii) Binary fission:
In this type of reproduction, a single organism gets divided into two. This type of reproduction takes place in Amoeba. The nucleus of the Amoeba gets divided into two followed by division of their bodies, each part getting one nucleus and developing into separate individual.

Question 7.
In which female reproductive organ does the embryo get embedded?
Answer:
Uterus.

Question 8.
What is metamorphosis? Give examples.
Answer:
Drastic changes which take place during the development of an animal is called metamorphosis. Animals like frog, butterfly undergo metamorphosis.

Question 9.
Differentiate between internal fertilisation and external fertilisation.
Answer:
Internal fertilisation takes place inside the body of the female while the external fertilisation takes place outside the body of the female.
In case of internal fertilisation sperms are ejaculated in female’s body by the male. In external fertilisation sperms are discharged in I open.

Question 10.
Complete the cross-word puzzle using the hints given below.
Across:
1. The process of the fusion of the gametes.
6. The type of fertilization in hen.
7. The term used for bulges observed on the sides of the body of Hydra.
8. Eggs are produced here.

Down:
2. Sperms are produced in these male reproductive organs.
3. Another term for the fertilized egg.
4. These animals lay eggs.
5. A type of fission in amobea.

Answer:

Extended Learning – Activities And Projects

1. Visit a poultry farm. Talk to the manager of the farm and try to find out the answers to the following:
(a) What are layers and broilers in a poultry farm?
(b) Do hens lay unfertilised eggs?
(c) How can you obtain fertilised and unfertilised eggs?
(d) Are the eggs that we get in the stores fertilised or unfertilised?
(e) Can you consume fertilised eggs?
(f) Is there any difference in the nutritional value of the fertilised and unfertilised eggs?
Answer:
For self attempt.

2. Observe live hydra yourself and learn how they reproduce by doing the following activity:
During the summer months collect water weeds from ponds or ditches along with the pond water and put them in a glass jar. After a day or so you may see several hydra clinging to the sides of the jar.

Hydra is transparent, jelly-like and with tentacles. It clings to the jar with the base of its body. If the jar is shaken, the hydra will contract instantly into a small blob, at the same time drawing its tentacles in.

Now take out few hydras from the jar and put them on a watch glass. Using a hand lens or a binocular or dissection microscope, observe the changes that are taking place in their body. Note down your observations.
Answer:
For self attempts.

3. The eggs we get from the market are generally the unfertilized ones. In case you wish to observe a developing chick embryo, get a fertilized egg from the poultry or hatchery which has been incubated for 36 hours or more. You may then be.able to see a white disc-like structure on the yolk. This is the developing embryo. Sometimes if the heart and blood vessels have developed you may even see a red spot.
Answer:
For self attempt.

4. Talk to a doctor. Find out how twinning: occurs. Look for any twins in your neighbourhood, or among your Mends. Find out ifthe twins are identical or non-identical. Also find out why identical twins are always of the same sex? If you know of any story about twins, write it in your own words.
You could visit the following website for information on twins: www.keepkidshealthy.com/twins/ expecting_twins.html.
For more information , on animal reproduction, you can vjsit:

• www.Saburchill.com/chapters/ chap0031.html
• healthhowstuffworks.com/human- reproduction.htm
• www.teenshealth.org/teen/sexual_health

Answer:
For self attempt.

HBSE 8th Class Science Reproduction in Animals Important Questions and Answers

Very Short Answer Type Questions

Question 1.
Name different modes of reproduction.
Answer:
Sexual reproduction and asexual reproduction.

Question 2.
Define sexual reproduction.
Answer:
When male and female organisms are involved in reproduction, it is called sexual reproduction.

Question 3.
Define asexual reproduction.
Answer:
When only single parent involved, reproduction is called asexual reproduction.

Question 4.
What is another name for ovum or sperm?
Answer:
Gametfe.

Question 5.
What is fertilization?
Answer:
When male and female gametes fuse, it is called fertilization.

Question 6.
What is formed when male and female gametes fuse?
Answer:
Zygote.

Question 7.
Name female reproductory organs.
Answer:
Ovaries, oviduct, uterus.

Question 8.
Name male reproductory organs.
Answer:
Testes, sperm ducts and penis.

Question 9.
Name the female gamete produced by ovaries.
Answer:
Ova.

Question 10.
Which male organ produce male gamete?
Answer:
Testes.

Question 11.
Name male gamete produced by testes.
Answer:
Sperms.

Question 12.
Name the hind of fertilization *hich take, pUce inside fem.le. body.
Answer:
Internal fertilization.

Question 13.
What kind of fertilization takes place in humans?
Answer:
Internal fertilization.

Question 14.
What type of fertilization takes place in frogs?
Answer:
External fertilization.

Question 15.
What does a zygote develop into?
Answer:
Embryo.

Question 16.
Where does an embryo grow in case of internal fertilization?
Answer:
In uterus.

Question 17.
What does an embryo grow into?
Answer:
Foetus.

Question 18.
Where does an embryo grow in case of external fertilization?
Answer:
Out side in open.

Question 19.
What are the animals called, who give birth directly to young one?
Answer:
Viviparous animals.

Question 20.
Give at least two examples of viviparous animals.
Answer:
Humans and cows.

Question 21.
What are the animals called, who lay eggs first?
Answer:
Oviparous animals.

Question 22.
Give any two examples of oviparous animals.
Answer:
Hen, Frog.

Question 23.
How many developing stages an egg of a frag undergoes to become an adult?
Answer:
Three: Egg, Tadpole, larvae, adult.

Question 24.
What do we call the sudden and extreme changes taking place during the development of an animal?
Answer:
Metamorphosis.

Question 25.
Name any two methods of asexual reproduction.
Answer:
Budding and Binary fission.

Question 26.
Name any animal undergoing budding for reproduction.
Answer:
Hydra.

Question 27.
Name tuny animal undergoing Binary fission to reproduce,
Answer:
Amoeba.

Short Answer Type Questions

Question 1.
What is reproduction? Why is it important?
Answer:
Reproduction is giving birth to organisms of same kind. Reproduction is important to continue life on earth and to maintain different special characters of different species.

Question 2.
What are different modes of reproduction?
Answer:
Reproduction takes place by two methods. In one method a single parent is involved in the process of reproduction. This is called asexual reproduction. In second method both male and female i.e. both parents are involved in the process of reproduction. This kind of reproduction is called sexual reproduction.

Question 3.
What are the names of male reproductory organs in human beings?
Answer:
In human beings male reproductory organs are a pair of testes, sperm ducts and a penis. Testes are responsible for producing male gametes called sperms. They are transported to the sperm ducts and through the penis, they are ejaculated in female body.

Question 4.
Explain the reproductory organs of female in human beings.
Answer:
In human beings the female reproductoiy organs are a pair of ovaries, oviducts or fallopian tubes and the uterus. Ovaries are responsible to produce female gamete called ova, which fertilize with male sperm in female fallopian tube and travels to uterus for its development into embryo and the foetus.

Question 5.
Describe the human male and female gametes.
Answer:
In human beings the males produce the gamete called sperms. Sperms are very small in size. They have a head with a middle piece which end into a tail. It is a single cell. Similarly, female gamete ova is produced by ovaries. Every ova is a single cell and one matured ova is released by one ovary every month.

Question 6.
What is fertilisation?
Answer:
When a male and a female gamete come in contact with each other they fuse. The male sperm enters the female ova and the nucleus of the sperm fuses with nucleus of the ova and results into a single nucleus. This whole process is called fertilization. In short fertilisation is the fusion of male and female gametes.

Question 7.
Explain how external fertilization takes place?
Answer:
In this case the females lay eggs in slow moving streams. The males also release sperms on this cluster of eggs. The sperms move in water with the help of tail and when come in contact with egg, they get fertilized.

Question 8.
How is an embryo formed put of a zygote?
Answer:
Zygote is a single cell formed by the fusion of male and female gametes. It undergoes repeated numbers of division to form a lot of many cells, so that the limbs and other parts can be developed. Thus a single zygote gets divided to form an embryo.

Question 9.
How is an embryo formed in case of hens?
Answer:
In hens zygote divides many times and reaches the oviduct. During this a protective outer coating is formed around the embryo. The complete embryo develops inside this protective shell. This embryo is laid by the hen along with the shell as an egg. This egg finally hatches after ‘ three weeks to produce chick.

Question 10.
What is budding?
Answer:
Budding is an asexual method of reproduction in animals. It needs only a single parent to reproduce. The body of the animal starts developing a small bulging structure called bud which slowly grows and have itself disconnected from the parent animal and becomes a separate individual. This is called budding. Animals like hydra reproduce through budding.

Question 11.
What do you mean by binary fission?
Answer:
Binary fission is a method of asexual reproduction. In this method the body of the animal divides into two halves. The nucleus of the body divides into two and this is followed by the division of the whole body. So, two organisms get produced with separate nuclei. Animals like Amoeba reproduce by this method.

Question 12.
What is cloning?
Answer:
Cloning is a method of producing an identical organism, a body part or only a cell. The produced organism or cell is completely identical to its original organism or cell. This method has been used many times in animals to produce identical clones.

Long Answer Type Questions

Question 1.
What do you mean by reproduction? Write about different modes of reproduction.
Answer:
Reproduction is the process of producing young ones of the same kind. Reproduction is a very important process. It is the only means of keeping the life on the earth.
There are two modes of reproduction:
(i) Sexual Reproduction:
Reproduction process in which a male and a female parents are involved is called sexual reproduction. In this process both parents produce gametes which fertilize to produce a zygote, which further develops into a baby. Human beings, cows, dogs etc. reproduce sexually.

(ii) Asexual Reproduction:
When a single parent is responsible for producing a young one, it is called asexual reproduction. Budding, fragmentation, spore formation Binary fission etc. are different methods of asexual reproduction. Microorganisms like Hydra, Amoeba, bacteria etc. reproduce asexually.

Question 2.
Draw and describe the male reproductive organs in humans.
Answer:
Male reproductive organs consist of a pair of testes, sperm ducts and penis. Testes are responsible for producing male gamete called sperm. Sperm is very small in size. It has a head, a middle piece and a tail. Sperms travel through sperm ducts and penis, and are released in female body for fertilization.

Question 3.
Draw and explain the Female Reproductive organs in human.
Answer:
Female reproductive organs consist of a pair of ovaries, oviduct or fallopian tubes and uterus.

Ovaries produce the female gamete called Ova. Every month an ovary produces an ovum. The ovum and sperm fertilize inside fallopian tubes and the fertilized zygote travels to the uterus and attach with its wall to develop into the foetus.

Question 4.
What is fertilization? How does it take place?
Answer:
Fertilization is the process by which the male and female gametes fuse to form the zygote. The sperms from a male are transferred into the female body. They swim to the fallopian tubes with help of their tails and one of them enters the ovum to fertilize. When the sperm enters the ovum, the nucleus of both the gametes fuse with each other to form the fertilized zygote.

The fertilized egg is called zygote. This zygote develops into foetus by repeated cell division. When the fertilization takes in the body of female, it is called internal fertilization. But many animals release their gametes into water and fertilization takes place outside the body of female, then the fertilization is called the external fertilization.

Question 5.
What is asexusal reproduction? Describe different methods of asexual reproduction.
Answer:
The reproduction in which only a single parent is involved is called asexual reproduction. This type of reproduction takes place mostly in microoganisms. Following are the methods of asexual reproduction:
(i) Budding:
This type of reproduction takes place in Hydra. The body of the hydra starts developing small bulges. These bulges are called buds. These buds grow in size and finally get detached from its body and become a separate individual.

(ii) Binary Fission:
This type of reproduction takes place in Amoeba. The body of the organism divides into two. The nucleus of the organism divides into two and then the body of Amoeba divides, each part getting each nucleus and thus becoming two separate individuals.

Reproduction in Animals Class 8 HBSE Notes

1. Each living being reproduce to give birth to young ones exactly like them.
2. The process by which young ones are produced is called reproduction.
3. Reproduction is of two types: Sexual reproduction and asexual reproduction.
4. When a male and a female gamete fuse to give birth to a young ones, then it is called sexual reproduction.
5. When a single parent is involved in reproduction, then it is called asexual reproduction.
6. Reproductive organs in males and females are different. In females the reproductive organs are ovaries oviducts and uterus. In males the reproductive organs are a pair of testes, sperm ducts and penis.
7. Ovaries produce female gamete called ovum and male gamete called sperms are produced by testes.
8. Ovum and sperm fuse to form egg called Zygote. The process of fusion of ovum and sperm is called fertilization.
9. Fertilization is of two types: When it takes place inside the females body, then it is called internal fertilization, but when ovum and sperms fuse out side the body, it is called external fertilization.
10. Embryo is formed from the zygote by repeated divisions, which grows in the uterus of the female in case of internal fertilization. Embryo grows into foetus when it gets well developed limbs.
11. When animals give birth to a young one it is called a viviparous animals e.g. man, cow etc. When animals lay eggs, they are called oviparous animals e.g. hen, butterfly, etc.
12. In asexual reproduction organisms reproduce by budding binary fission, fragmentation etc.

Haryana State Board HBSE 8th Class Science Solutions Chapter 8 Cell Structure and Functions Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 8 Cell Structure and Functions

HBSE 8th Class Science Cell Structure and Functions Textbook Questions and Answers

Question 1.
Indicate whether the following statements are True (T) or False (F).
(а) Unicellular organisms have one-celled body. (T/F)
(б) Muscle cells are branched structures. (T/F)
(c) The basic living structure of an organism is an organ. (T/F)
(d) Amoeba has irregular shape. (T/F)
Answer:
(a) True
(b) True
(c) False
(d) True

Question 2.
Make a sketch of the human nerve cell. What function do nerve cells performs?
Answer:
Functions of human nerve cell:
(i) Nerve cells receive messages from different parts of body.
(ii) They further transfer these message to brain and brain further send commands for functioning Long Branched Nerve Cell of different organs.

(iii) They coordinate functioning of different organs of body.

Question 3.
Write short notes on the following:
(а) Cytoplasm
(b) Nucleus of a cell.
Answer:
(a) Cytoplasm:
Cytoplasm is a jelly like substance which is present between the cell membrane and the nucleus. Various other organelles of cells are present in the cytoplasm. Cytoplasm is made up of chemical substances like carbohydrates, proteins and water. These chemical substances are present in cells of all types and sizes.

(b) Nucleus of a cell:
Nucleus is the master of the cell. It commands all the functioning of the cell. It is generally located in the centre of the cell and is spherical in structure. A membrane called nuclear membrane separates it from cytoplasm. It contains the genetic material (DNA, RNA) in it. This porous membrane allows the transfer of material in the nucleus and cytoplasm. Nucleus contains a dense body called nucleolus which actually contain chromosomes the genetic material.

Question 4.
Which part of the cell contains organelles?
Answer:
Cytoplasm.

Question 5.
Make sketches of animals and plant cells. State three differences between them. Answer:

Question 6.
State a difference between eukaryotes and prokaryotes.
Answer:
Prokaryotes do not have a well designed nuclear membrane, while Eukaryotes have a well designed nuclear membrane.

Question 7.
Where are chromosomes found in a cell? State their function.
Answer:
Chromosomes are found in the nucleus of a cell. Their function is to carry characteristic features of parent cells to the daughter cell i.e. from parent to offsprongs.

Question 8.
‘Cells are the basic structural units of living organism’. Explain.
Answer:
Cells are the basic structural units of living organisms because lot of cells unit to form and many tissues form an organ. And organs combine to form a complete body, so cell is the basic structural unit of an organism. All basic function for the survival of an organism take peace inside cells so they are the basic functional units of a living being.

Question 9.
Explain why chloroplasts are found only in plant cells?
Answer:
Chloroplasts are only found in plant cells because they are required for the food making process of plants called photosynthesis.

Question 10.
Complete the following crossword with the help of clues given below:
Across
1. This is necessary for photosynthesis.
3. Term for component present in the cytoplasm.
6. The living substance in the cell.
8. Unit of inheritance present on the chromosomes.

Down
1. Green plastids.
2. Formed by collection of tissues.
4. It separates the contents of the cell from the surrounding medium.
5. Empty space in the cytoplasm.
7. A group of cells.

Answer:

Extended Learning – Activities And Projects

1. Visit a laboratory for senior secondary students in your school or in a neightbouring school. Learn about the functioning of a microscope in the laboratory. Also observe how a slide is observed under the microscope,
Answer:
For self attempt.

2. Talk to the senior biology teacher in your school or a neighbouring school. Find out if there are diseases which are passed on from parents to the offspring. Find out how these are carried and also if these diseases can be treated. For this you can also visit a doctor.
Answer:
There are certain diseases which are passed on from parent to the offspring. Diseases like diabites, heart diseases, certain skin diseases like leukoderma, etc. are genetic diseases.

3. Visit an agriculture extension centre in your area. Find out about genetically modified (GM) crops. Prepare a short speech for your class on this topic. You may visit www.usc.ernet.in / currsci / sep2520Ql/ 655.pdf
Answer:
For self attempt.

4. Find out about Bt cotton from an agriculture expert (or from envfor.nic.in/ division/csnrv/btcotton/b gnote.pdf). Prepare a short note on its advantages / disadvantages.
For more on cell, visit: www.enchantedlearning.com/subjects/ plants/ cell/
Answer:
For self attempt.

HBSE 8th Class Science Cell Structure and Functions Important Questions and Answers

Very Short Answer Type Questions

Question 1.
Define a cell.
Answer:
A cell is the basic structural and functional unit of living things.

Question 2.
Who discovered cell?
Answer:
Robert Hooke.

Question 3.
Name three important parts of cell.
Answer:
(i) Cell membrane
(ii) Cytoplasm
(iii) Nucleus

Question 4.
In which cells, cell wall is present?
Answer:
In plant cells.

Question 5.
Give three examples of unicellular organisms.
Answer:
Amoeba, Paramecium, Chlamydomonas.

Question 6.
Where are chromosomes present in a cell?
Answer:
Nucleus.

Question 7.
Name the cell part that has tiny holes.
Answer:
Cell Membrane

Question 8.
Which cell organelle is found only in animal cell?
Answer:
Centrosome.

Question 9.
Name the cells organelle which is found only in plant cell.
Answer:
Plastids.

Question 10.
How do cells increase in numbers?
Answer:
By cell division.

Question 11.
Which organelle is called the ppwer house of the cell?
Answer:
Mitochondria.

Question 12.
Which organelle is called suicidal bags of the cell?
Answer:
Lysosomes.

Question 13.
What does mitochondria do?
Answer:
It prepares food for plants.

Question 14.
What does chromosomes do?
Answer:
Transfer chracters from one generation to another generation.

Question 15.
What does ribosomes do?
Answer:
They help in synthesis of proteins.

Question 16.
Name plastids found in plant cells.
Answer:
Chloroplasts, Leucoplast and chromoplast.

Question 17.
What is the unit of measuring the size of the cell?
Answer:
Microns.

Question 18.
Name the longest cell.
Answer:
Nerve cell in animal.

Question 19.
Name the heaviest animal cell.
Answer:
Ostrich Egg.

Question 20.
Name the largest plant cell.
Answer:
Acetabulum.

Question 21.
Name the smallest plant cell.
Answer:
Bacteria.

Short Answer Type Questions

Question 1.
Why cells are called building blocks of life?
Answer:
Cells like bricks of a building are basic structural units of living organisms. Buildings differ from each other, organism also differ from each other. Both are basic unit of structure. So, they are called building blocks of life.

Question 2.
Why are the mitochondria known as the power housd of the cell?
Answer:
They are rod shaped and very minute. They are concerned with the release of energy from food during respiration. Because of this, they are often referred to as the power house of the cell.

Question 3.
What are the cell organelles? What are their functions?
Answer:
Cell organelles are small active living structures found in cytoplasm of cell. Each organelle has different structure and performs different function for cell. They are endoplasmic reticulum, Plastides, Mitochondria, Ribosomes, Golgi bodies, Centrosomes, Lysosomes, Vacoules.

Question 4.
What is meant by protoplasm?
Answer:
The cytoplasm surrounded by the cell membrane and enclosing the nucleus together constitute the protoplasm. Protoplasm in other words, includes the cell membrance, the nucleus and the Cytoplasm.

Question 5.
Name four elements which form major part of protoplasm?
Answer:
Ninety nine percent of protoplasm by its weight is made up of four elements. Namely; Carbon, Hydrogen, Nitrogen and Oxygen. It also contains other elements such as H20, Carbohydrates, fats, proteins and mineral acids. Both elements and compounds in unique combination provide living nature to the protoplasm.

Question 6.
Why cells could not be observed before 17th century?
Answer:
The main reason was that the size of the majority of the cells are too small to be invisible to the unaided eye and at that time microscope was not discovered. So, the cell could not be observed before 17th century.

Question 7.
Why Hooke had to take thin slices of cork?
Answer:
The cork was solid and the details of cork could not seen in solid state. So he made thin slices to see the details of the cork. He saw space in cork slice which appeared like honey comb, called these compartments as cells.

Question 8.
What do you know about cell shape?
Answer:
Cells are of diverse shapes. Some cells are like Amoeba and white blood cells of our blood. They continuously change their shape. Most cells, however, maintain a constant shape all through their existence.

Question 9.
Write about size variation of the cells.
Answer:
Cells vary in their size. The smallest known cell is bacteria measuring about 0.5 micrometre. Nerve cell is up to 1 metre long. The heaviest cell is of ostrich and acetabulum is the largest unicellular algae which is about 10 cm long. Majority of cells in plants and animals range from 20 to 30 microns in diameter.

Question 10.
Write a short note on cell numbers.
Answer:
Cells are of two types depending upon their number. Some cells exist single in number. The organism consisting of a single cell are called unicellular organisms. The organisms which consist of two or more than two cells are called multicellular organisms. Human body consists of more than a trillion of cells. Amoeba,Paramecium etc. are unicellular organisms.

Question 11.
What is nucleolus?
Answer:
Nucleolus is a small spherical dense body present in the nucleus. It is only visible, with a microscope of a higher magnification.

Long Answer Type Questions

Question 1.
How do you differentiate protoplasm from cytoplasm?
Answer:
Protoplasm:
The cytoplasm surrounded by the cell membrane and enclosing the nucleus together constitute the protoplasm. In other words the cell membrane, the cytoplasm and the nucleus constitute pr’otoplasm.

Cytoplasm:
It is jelly like substance occupied most of the inside of the cell. It occupies the space between the cell membrane and the nucleus. All the life functions take place in the cytoplasm. It contains many important tiny structures called the organelles, which performs the various life functions.

Question 2.
Write the functions of cell organelles.
Answer:
(i) Mitochondria: It performs the function of respiration provide the cell with energy.
(ii) Endoplasmic-reticulum: It is a network of membrane, it provides large surface area for life function to take place.
(iii) Chloroplasts: These are green in colour, contain green pigment chlorophyll which help in food manufacturing in plants.
(iv) Golgi complex: These collect and distribute substances made in the cell. Synthesis and secretions of many materials.
(v) Lysosomes: Certain enzymes which help in breaking down or destroying various unwanted materials of cell.
(vi) Centrioles and centrosome: It helps in cell division in animal cells.
(vii) Ribosomes: They help in protein synthesis.
(viii) Vacoules: These are generally stored inside clear space in the cytoplasm.
In animal cells they are very small. In plant cells they are large and greater in number.

Question 3.
Differentiate between the plant cell and the animal cell.
Answer:

Animal Cell	Plant Cell
(i) Cell wall is absent.	(i) A rigid cell wall is present.
(ii) Chloroplasts are absent.	(ii) Chloroplasts are present.
(iii) Centrosome is present near the nucleus.	(iii) Centrosome is absent.

Cell Structure and Functions Class 8 HBSE Notes

1. All organisms are made of small basic structural and functional units.
2. These smallest functional units are called cells.
3. Robert Hooke observed a cell for the first time in 1665.
4. Cells can be defined as the basic structural and functional unit of life.
5. Cells are of different size and shape.
6. Living Organisms made up of a single cell are called unicellular organisms.
7. All unicellular organisms are microscopic organism e.g. Amoeba, Paramecium etc. i.e. they cannot be seen with naked eyes.
8. Some cells can be seen with naked eyes without any aid e.g. egg of a hen.
9. In unicellular organisms, the single cell perform all the function necessary for living.
10. A cell has different parts. These small parts of the cell are called organelles.
11. A cell is made up of cell membrane, which contains all the organelles in it.
12. All cell organellies are contained in cytoplasm.
13. In the centre of the cytoplasm nucleus is situated, which is the brain of the cell.
14. Mitochondria, Endoplasmic reticulum, chloroplasts, golgi complex, lysosomes, centrioles, and ribosomes are other cell organelles.
15. Cells which don’t have a well organized nuleus are called the karyotic cells. In these cells the nucleus lacks the nuclear membrane.
16. The cells of plants are a bit different from that of animals.
17. In animals, cell wall, chloroplast, chromosomes, vacoules are absent, while they are present in plant cells.
18. Green leaves have a special organelle called chlorophyll i.e. the Green plastids (chloroplasts) which helps in the process of photosynthesis.
19. Different colours of plastids give different colours to plants.

Haryana State Board HBSE 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 7 Conservation of Plants and Animals

HBSE 8th Class Science Conservation of Plants and Animals Textbook Questions and Answers

Question 1.
Fill in the blanks:
(a) A place where animals are protected in their natural habitat is called ………….. .
(b) Species found only in a particular area is known as ………….. .
(c) Migratory birds fly to far away places because of …………. changes.
Answer:
(a) wildlife sanetuary
(b) Endemic species
(c) climate.

Question 2.
Differentiate between the following:
(a) Wildlife sanctuary and biosphere reserve.
(b) Zoo and wildlife sanctuary.
(c) Endangered and extinct species.
(d) Flora and fauna.
Answer:
(a) Wildlife sanctuary is a place where wild animals are protected and preserved. Here poaching or capturing any animal is strictly prohibited. Biosphere reserves are the protecting areas meant for only conservation of biodiversity i.e. animals and plants and even the microorganisms. It also helps to maintain the culture of that area. It contains many wildlife sancturies, national parks.

(b) Zoos are smaller places having some animals protected for the public view, while wildlife sancturies protect and conserve wild animals in their natural habitats. They are spread in vast areas.

(c) Endangered species are those species which are at the verge of extinction and which are required to be protected and conserved, while extinct species are those which no more exist on the earth.

(d) Flora is the term used for wide variety of plants while fauna is used to refer to all the varieties of animals.

Question 3.
Discuss the effects of deforestation on the following:
(a) Wild animals
(b) Environment
(c) Villages (Rural areas)
(d) Cities (Urban areas).
(e) Earth
(f) The next generation.
Answer:
(a) Wild animals:
When forests are cut, they leave many wild animals unsheltered. Their habitat is snatched away from them and they are left to die without their natural shelter.

(b) Environment:
Environment is adversely effected by deforestation as ecological balance is disturbed. Carbondioxide is not absorbed by plants and it gets accumulated to cause global warming.

(c) Villages (Rural areas):
Villages are depended upon forests to large extent. They are closely related to forests. Some adjoining villages have to face the wrath of wild animals as unhabitated animals run to nearby villages and cause danger to them. Morever they are devoid of other benefits like fruits, fuel, wood etc. they get from forests.

(d) Cities (Urban areas):
Cities are not directly effected by the cutting of forests because they are away from forests. But changes in climate effect cities. Calamities like flood and droughts do not spare cities.

(e) Earth:
Earth is the worst effected by deforestation. Its fertile land gets converted into deserts and its temperature rises. Its environment and climate changes.

(f) The Next generation:
The next generation will not be able to see many beautiful and attractive flora and fauna. They will not get a clean and cool environment. They will have to breath poisonous gases and have to live in jungles of concrete.

Question 4.
What will happen if:
(a) we go on cutting trees.
(b) the habitat of an animal is disturbed.
(c) the’top layer of soil is exposed.
Answer:
(a) We go on cutting trees:
If we go on cutting trees, the earth will loose its top fertile soil and get converted to desert. The ecological balance will get disturbed and floods and droughts will become more frequent. Many animals will loose their shelter and there will be a scarcity of things like fruits, paper, etc. we get from forests.

(b) When the habitat of an animal is disturbed, it becomes unprotected and unconserved. It becomes prone to extinction and if not conserved and protected, it will stop to exist anymore on the earth.

(c) When the top layer of the soil is exposed, the humus is lost and fertile soil gets converted into dry sand particles. It is called desertification.

Question 5.
Answer in brief:
(а) Why should we conserve biodiversity?
(b) Protected forests are also not completely safe for wild animals. Why?
(c) Some tribes depend on the jungle. How?
(d) What are the causes and consequences of deforestation?
(e) What is Red Data Book?
(f) What do you understand by the term migration?
Answer:
(a) We should conserve biodiversity to save it from becoming extinct.

(b) Protected forests are also not completely safe for wild animals because the poachers have found access in these areas an,d still kill the wild animals inside these protected areas.

(c) Some tribes are totally dependent on forests for their food, shelter, clothes and other requirements.

(d) Causes of the deforestation are growing urbanization and industrialization. Consequences are the desertification and natural calamities. It has also rendered many species of plants and animals unprotected and unconserved.

(e) Red Data Book is the record book and source book of all the endangered animals and plants. Different record books are maintained for endangered animals and endangered plants.

(f) The term migration means the phenomenon of periodical movement of a species of brids from its owu habitat to some other habitat due to changes in climate. It is for the purpose of breeding and other specific purposes.

Question 6.
In order to meet the ever- increasing demand in factories and for shelter, trees are being continually cut. Is it justified to cut trees for such projects? Discuss this in your class and prepare a brief report.
Answer:
It is not justified to cut forests for any project. We not only cut forests, we snatch away shelters from many plants, animals and birds. They also disturb the ecological balances and cause many natural calamities. So, we should preserve and protect our forests.

Question 7.
How can you contribute to the maintenance of green wealth of your locality? Make a list of actions to be taken byyou.
Answer:
We can grow new plants in our locality. Take turns to water them and take care of them. The existing plants should be properly nourished. All the residents should be taught about the coming dangers due to deforestation like global warming etc. They should be encouraged to help in the maintenance of green wealth of our locality.

Question 8.
Explain how deforestation lead to reduced rainfall.
Answer:
Deforestation leads to reduce rainfall because plants are the main agents to maintain the water cycle in the environment. Plants will not absorb water from the soil and will not evaporate water from their leaves to form clouds. If clouds will not be formed then how can we expect rainfall.

Question 9.
Find out about national parks in your state. Identify and show their location on the outlipe map of India.
Answer:
For self attempt.

Question 10.
Why should paper be saved? Prepare a list of the ways by which you can save paper.
Answer:
Paper is manufactured by using, pulps of tree bark. If we will keep on cutting forests indiscriminately, then where will we get pulp from. We should save paper to protect our trees, because paper can be recycled to make- new paper. We should not throw papers here and there. Newspapers, old books, notebooks and other papers should be collected and sold to kabadiwala, so that he can further supply it for recycling.

Question 11.
Complete the word puzzle:
Down .
1. Species on the verge of extinction.
2. A book carrying information about endangered species.
5. Consequence of deforestation.
Across
1. Species which have vanished.
3. Species found only in a particular habitat.
4. Variety and variability of a plant, animal and microorganisms.

Answer:

Extended Learning – Activities And Projects

1. Plant at least five different plants in your locality during this academic year and ensure their maintenance till they grow.
Answer:
For self attempt.

2. Promise yourself that this year you will gift at least 5 plants to your friends and relatives on their achievements, or on occasions like birthdays. Ask your friends to take proper care of these plants and encourage them to gift plants to their friends on such occasions. At the end of the year count the plants that have been gifted through this chain.
Answer:
For self attempt.

3. It is justified to prevent tribals from staying in the core area of the forest? Discuss the matter in your class and note down the points for and against the motion in your notebook.
Answer:
It is not justifiable in my Qpinin to prevent triabls from the core area of a forest. It is their natural habitat. They are not any threats to animals and plants as their life is centred around plants and animals. They don’t destroy forest or kill animals unnecessarily. Forest for them is an important as for other animals and plants.

4. Study the biodiversity of a park nearby. Prepare a detailed report with photographs and sketches of the flora and fauna.
Answer:
For self attempt.

5. Make a list of the new information you have gathered from this chapter. Which information did you find the most interesting and why?
Answer:
(i) We have learnt how deforestation is destoryed biodiversity.
(ii) We have learnt about the actual meaning ofbiodiversity.
(iii) We have also gathered new information about extinct and endangerous animals.
(iv) We did not know anything about Red Data Book-but know we have learnt about it through this lesson.

6. Make a list of various uses of papers. Obseve currency notes carefully. Do you find any difference between a currency paper and paper of your notebook? Find out where currency paper is made.
Answer:
Paper is very useful for us.
(i) Our book and notebooks are all made up of paper.
(ii) Most of our currency is made up of paper.
(iii) All legal information and other important information are encoded on papers.
(iv) Paper is used to make bags, containers, package materials, etc. The paper used to make currency is stiffer than the normal paper and is transparent to some extent.

7. Karnataka Government had launched “Project Elephant” to save Asian elephants in the state. Find out about this and other such campaigns launched to protect threatened species.
Answer:
For self attempt.

Activities

Activity No. 7.1

Add more causes of deforestation to your list and classify them into natural and man-made.
Answer:
Natural causes of deforestation:
(i) lightning fires.

Man-made causes of deforestation:
(i) animal grazing.
(ii) Wood for fuel making houses.
(iii) Wood for manufacuring of paper.

Activity No. 7.2

Animal life is also affected by deforestation. How? List the points and discuss them in your class. ,
Answer:
(i) Animals loose their shelter as trees are out.
(ii) There is shortage of food for animals due to deforestation.
(iii) Animals become easy prey to hunters and bigger animals.
(iv) Food chains are disturbed.
(v) Animals have to bear the bad effects of natural calamities.

Activity No. 7.4

List the factors disturbing the biodiversity of your area. Some of these factors and human activities may disturb the biodiversity unknowingly. List these . human activities. How can these be checked? Discuss in your class and write a brief report in or notebook.
Answer:
Main factor affecting biodiversity of an area is cutting of trees and using the forest land for construction and industrialization. Excessive rains or droughts also offer the biodiversity of an area. Certain human activities which give rise to polluting end products also disturb the biodiversity unknowningly. When plants and animals do get clean environment they either fall ill or die, thus disturbance in biodiversity.

Activity No. 7.7

Visit a nearby zoo. Observe the conditions provided to the animals. Were they suitable for the animals? Can animals live in artificial setting instead of their natural habitats? In your opinion, will the animals be confortable in a zoo or in their natural habitat?
Answer:
Conditions provided in a zoo can never be compared with the natural habitat. The condition in a zoo are not exactly suitable for animals, although it is tried best to provide best living conditions to the animals in a zoo. But in my opinion animals be most comfortable in their natural habitat.

HBSE 8th Class Science Conservation of Plants and Animals Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is cutting of forests called?
Answer:
Deforestations

Question 2.
Write any one cause of deforestation.
Answer:
Industrialization.

Question 3.
Name any one natural cause of deforestation.
Answer:
Forest fires.

Question 4.
Write any one consequence of deforestation.
Answer:
Increasing temperature of earth.

Question 5.
What is the process of conversion qf fertile soil into sand called?
Answer:
Desertification.

Question 6.
What are places where wild animals are protected called?
Answer:
Wildlife sanctuary.

Question 7.
What is the part of earth, which supports the biodiversity called?
Answer:
Biosphere reserve.

Question 8.
Name two wildlife sanctuaries hosted by Panchmarhi biosphere reserve.
Answer:
Bori and Panchmarhi.

Question 9.
What do you mean by Flora?
Answer:
All plants found in a particular area.

Question 10.
What do you mean by Fauna?
Answer:
All animals in a particular area.

Question 11.
What are species found only in a restricted area called?
Answer:
Endemic species.

Question 12.
Name any fauna of Panchmarhi Biosphere,reserve.
Answer:
Bison.

Question 13.
Name any three endangered species protected in our wildlife sanctuaries.
Answer:
Black buck, white eyed buck, golden cat.

Question 14.
What do National Parks preserve?
Answer:
Flora, fauna, landscape and historical objects.

Question 15.
Which is the first Reserve Forest of India?
Answer:
Satpura National Park.

Question 16.
Which prehistoric evidences of human life are found in Satpura National Park?
Answer:
Rock shelters of primitive humans.

Question 17.
When was Project Tiger launched?
Answer:
1st April, 1973.

Question 18.
What are the animals facing the danger of extinction are called?
Answer:
Endangered animals.

Question 19.
Name any one extinct animal.
Answer:
Dinosaurs.

Question 20.
Name the record book having records of all endangered animals and plants.
Answer:
Red Data Book.

Question 21.
Name some migratory birds.
Answer:
Surkhab, Bar Headed Goose, Great Cormorant.

Question 22.
How many times a paper can be recycled?
Answer:
5-7 times.

Question 23.
What do we call the restocking the plants by growing new plants?
Answer:
Reforestation.

Question 24.
What is plantation of new plants called?
Answer:
Afforestation.

Question 25.
What is the revised Forest Policy of 1952 called?
Answer:
Forest Act, 1980.

Short Answer Type Questions

Question 1.
What do you mean by deforestation?
Answer:
Indiscriminate cutting of forests for urbanization and industrialization is called deforestation. In simple words, deforestation means to clear the forests and use the land for other purposes.

Question 2.
Write some natural causes of deforestation.
Answer:
Natural causes of deforestation are those causes which are not initiated by human beings. Natural phenomenon like lightening on forests cause major forest fires, which can bum a large area of forests. Forest fires due to intense heat cause spontaneous combustion and bums a vast area of forest. Similarly, floods and severe droughts also cause damage to forests.

Question 3.
Write a few consequences of deforestation.
Answer:
Deforestation. has dangerous consequences which prove fatal for wildlife and human life. It gives rise to severe droughts and floods. It converts the fertile land into desert. It increases the temperature of the earth which causes melting of polar ice and glaciers. Many important species of plants, animals and birds become extinct and other stands at the verge of extinction.

Question 4.
How deforestation reduces rainfall?
Answer:
Deforestation disturbs the water cycle and reduces the rainfall. Increased amount of carbondioxide in environment increases the temperature of the earth. Which means there is less amount of water left on the earth. This reduces the evaporation of the water to form clouds thus reduced rainfall.

Question 5.
What do you mean by biodiversity?
Answer:
Biological diversity means the variety of living things existing on earth and their inter-relationship, as well as their relationship with the environment. In other words, variety of plants, animals and microorganisms generally found in an area is called its biodiversity.

Question 6.
What do you mean by endemic species?
Answer:
Species of animals and plants which are only found in a particular geographical area is called endemic species. These plants and animals cannot be found in any other geographical area e.g., wild mango arid gaint squirrel is endemic species of Panchmarhi.

Question 7.
What do you mean by wildlife sanctuaries?
Answer:
Wildlife sanctuaries are the protected areas where wild animals are protected and conserved. The wild animals are provided with their natural habitat. Their poaching and capturing is strictly prohibited m these protected areas.

Question 8.
What is a National Park?
Answer:
National Park is the protected vast area which conserves animals, plants, landscapes and even the historical objects. They are very large areas and can even protect whole sets of ecosystems in them. India has many such National Parks like Satpura National Park, Kaziranga National Park, etc.

Question 9.
What are the endangered and extinct animals?
Answer:
Endangered animals are those which are facing the danger to their existence. They are threatened to stop existing on the earth, if not saved. The extinct animals are those which do not exist any more on the earth e.g. Dinosaurs.

Question 10.
What is ecosystem?
Answer:
An ecosystem comprises of all the plants, animals, microorganisms in a particular area alongwith its non-living components like climate, soil, river, deltas etc.

Question 11.
What do you know about Project Tiger?
Answer:
Project Tiger was launched by Gqf*rtnment of India on 1st April, 1973 to enusre the maintenance of a viable populati on of tigers in our country. Tigers are one of the endangered species, so to preserve it Project Tiger was launched.

Question 12.
Why do birds migrate?
Answer:
Birds migrate from one place to another due to change in climate and for specific purposes like breeding etc. When weather in their natural habitat becomes cold they migrate to other lands covering long distances to lay eggs.

Question 13.
How does recycling of paper help preserving trees?
Answer:
Paper is made from the bark of trees. If used paper is recycled to make new papers, it means we do not have to cut more trees. So, recycling paper means protecting trees.

Question 14.
What do you mean by Habitat?
Answer:
Each species can live in particular environment according to their characteristics. So, the natural surroundings of a plant or animal species where they can grow, reproduce and live comfortably are called habitats, e.g. a lion can live in jungle, but not in a city. So jungle is the habitat of the lion.

Long Answer Type Questions

Question 1.
What is Deforestation? Write its causes.
Answer:
Deforestation means indiscriminate cutting of trees in forest. Forest lands are cleared to be used for urbanisation and industrialization.
Following are different causes of deforestation:
(i) Forest land is used for urbanization. As population is growing, so is growing the need for houses. So more and more land is required.
(ii) With growing population, industries are also growing. So the cleared land is used to set-up factories and industries.
(iii) Wood of forest is used for making furniture, doors, windows of buildings etc.
(iv) Wood is cut to use as fuel for cooking.
(v) Some natural causes like forest fires etc. also cause destruction of forests.

Question 2.
What are the consequences of deforestation? Explain.
Answer:
Deforestation has dire consequences. Following are the consequences of deforestation:
(i) Deforestation snatches away the natural habitat of many animals, plants and birds. It puts many species in endangered zone and many get extinct.
(ii) Deforestation causes natural calamities like floods, drought etc.
(iii) Reduced rainfall and increase in earth’s temperature has caused problems like Global warming.
(iv) Increased amount of carbondioxide and other gases pollute environment.
(v) Oxygen level is decreased as well as the water level.
(vi) Fertile top layer of soil gets converted into desert.

Question 3.
What is done for the conservation of wildlife?
Answer:
Various measures are taken to conserve wildlife. Reserved and protected areas like Biosphere reserve, Wildlife sanctuaries and National parks are formed.

Biosphere Reserves are the areas which support biodiversity and culture of the reserved area. Biosphere Reserve is a vast area which contains many other protected areas.

Wildlife Sanctuaries are the areas where wild animals are conserved and protected. It is the area which is restricted and activities like killing of animals and capturing of animals are strictly prohibited.

National Parks: National Parks are meant to protect and preserve flora, fauna, landscapes and historical objects of an area. They not only protect the living organisms, but also the non-living things of that particular area.

Question 4.
What do you mean by Endemic Species? Write about any three species endemic to India.
Answer:
Species of animals and plants comfined to certain specific geographical areas are called endemic species. Following are the three species of animals endemic to India.
(i) Lion-tailed macaque:
This animal got his name from its tail which is 25 cm in length and has a tuft at the end like that of lion’s which is black in colour. It is endemic to south-west India an is one of the most threatened primates.

(ii) Asiatic lion:
Asiatic lion is now endemic to Gir National Patk only as it is believed that the last remnants of this species are found in Gir National Park in Gujarat only.

(iii) Nilgiri ibex:
These stocky goats possessing short coarse fur and a bristly main are endemic to Nilgiri Hills and the Southern postion of the Western Ghats range in Tamil Nadu and Kerela. It is actually called Nilgiri Thar and Nilgiri ibex is its local name.

Question 5.
What is migration and why animals migrate?
Answer:
Movements of animals in large number from one place to another place to escape unfavourable conditions is called migration. Animals migrate for specific purposes. When the purpose is solved, they usually come back to their endemic area.

Migration can be due to unfavourable environmental conditions, eg. The Arctic Tern migrate to Antarctic to spend its winlers. Some birds of colder regions migrate to Asiatic countries during winters. This type of migration is called seasonal migration which occur in many species of insects, birds, marine mammals and herbivorous mammals.

Migration is also done for better food or water availability in other regions due to temperature and other climatic conditions.
Some species of animals and birds also migrate for the purpose of reproduction e.g. fresh watereeds go to saltwaters from freshwater to lay eggs.

Question 6.
What is poaching? How is it done by anti social elements and for what purpose?
Answer:
Illegal hunting of animals is called poaching. Anti-social element some time create a nexus with the forest staff for poaching; They hunt the animals for selling their skin, horn, fur and hides.

All valuable parts of these animals are used for various purposes and are sold at very high prices.
Uses for ornaments: The bones and other parts like trunks of elephants etc. are used to make ornaments.
Uses in medicines: The horns and bones of some animals like rhinoceros and tigers are used to prepare some traditional medicine specially in Asian countries.
For wall hanging and clothings: The skin, fur and hides are used for the clothing. Mufflers, coats, jackets, skirts etc. are made using leather and fur of the animals like cats, minks, bears foe fur, skin of alligators and snakes and deer and cattle are killed for leather.

Question 7.
Write a short note op migratory birds.
Answer:
Migratory birds are those birds which migrate from their natural habitat to far off areas for breeding. When the natural habitat o.f these birds become very cold, they fly off to distant lands to lay eggs, as climate there is suitable for their breding. They always fly to a specific area every year at a specific period. They migrate in groups to escape the inhospitable climate of their natural habitat.

Birds like Surkhab fly to India from Malyasia. Other birds like Bar Headed Goose, Great Cormorant etc. are also migratory birds.

Question 8.
Recycling of paper helps to protect forest and environment. Explain.
Answer:
Paper is made from trees. Innumerable trees are cut to manufacture paper. If we recycle used paper, we will not have to cut trees to manufacture new paper. Each paper can be recycled 5-7 times and can be used. If we do not throw paper here or there and collect it to be sold to the Kabadiwala, we sire saving our green wealth. It will also save the chemicals used to prepare paper and also the energy used for preparing it. The wastage mid garbage produced during this process will also be reduced and environment will remain clean.

Question 9.
How can we save CHIT green wealth?
Answer:
Our forests are our wealth. We should not destory them but conserve them. To conserve our forests, first of all we should stop cutting them. We should plant as many plants as we cut, so that the number of trees remain unchanged. People should be made aware of the bad effects of deforestation and they should be made familiar with the advantages of the trees for us. Community plantation programmes should be encouraged. Students should be encouraged to plant one plant every year. Plantation of trees is not sufficient. They need proper look after too. So, the tree we plant, should be nourished and taken care of.

Conservation of Plants and Animals Class 8 HBSE Notes

1. A vast variety of plants and animals exist on earth.
2. Deforestation is a threat to the survival of these plants and animals as major varieties of plants and animals are present in forests.
3. Indiscriminate cutting of forests is called deforestation. Land cleared by deforestation is used for other purposes too.
4. Trees cut from these forests are used to make furnitures, papers, houses and is also used as . fuel.
5. Deforestation causes floods, droughts, infertility of soil and many other natural calamities.
6. Soil looses humous due to deforestation and becomes sand, thus deforestation converts a fertile land into a desert and it is called desertification.
7. We should conserve our forests by planting more and more trees which is called afforestation. For conservation of animals; wildlife sancturies and hational parks are formed. They give shelter to our wildlife and help to preserve our endangered species of plants and animals.
8. Variety pf life existing on earth and their inter-relation is called biodiversity. In other words biodiversity is variety of plants and animals and microorganisms generally found in a specific area. Such life is supported by the area called Biosphere.
9. Species ofplants and animals exclusively found in a restricted area are called Endemic species. They are not found in any other geographical area.
10. These species which are at the verge of extinction are called endangered species.
11. Red Data Book contains a record of the endangered species.

Haryana State Board HBSE 8th Class Science Solutions Chapter 12 Friction Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 12 Friction

HBSE 8th Class Science Friction Textbook Questions and Answers

Question 1.
Fill in the blanks :
(a) Friction opposes the __________ between the surfaces in contact with each other.
(b) Friction depends on the __________ of surfaces.
(c) Friction produces __________.
(d) Sprinkling of powder on the carom board __________ friction.
(e) Sliding friction is __________ than the static friction.
Answer:
(a) relative motion
(b) nature
(c) heat
(d) reduces
(e) less.

Question 2.
Four children were asked to arrange forces due to rolling, static and sliding frictions in a decreasing order. Their arrangement are given below. Choose the correct arrangement:
(a) rolling, static, sliding
(b) rolling, sliding, static
(c) static, sliding, rolling
(d) sliding, static, rolling
Answer:
(c) static, sliding, rolling.

Question 3.
Alida runs her toy ear on dry marble floor, wet marble floor, newspaper and towel spread on the floor. The force of friction acting on the car on different surfaces in increasing order will be
(a) wet marble floor, dry marble floor, newspaper and towel.
(b) newspaper, towel, dry marble floor, wet marble floor.
(c) towel, newspaper, dry marble floor, wet marble floor.
(d) wet marble floor, dry marble floor, towel, newspaper.
Answer:
(a) wet marble floor, dry marble floor, newspaper and towel.

Question 4.
Suppose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of frictional force acting on it.
Answer:
Frictional force is acting opposite to the movement of book i.e. upwards.

Question 5.
You spill a bucket of soapy water on a marble floor accidently. Would it make it easier or more difficult for you to walk on the floor? Why?
Answer:
It is difficult to walk on a soapy floor because layer of soap makes floor smooth. The coating of soap reduces the friction and the foot cannot make a proper grip on the floor and it starts getting to slip on the floor.

Question 6.
Explain why sportsmen use shoes with spikes.
Answer:
Sportsmen use shoes with spike to increase the friction so, that their shoes do not slip while they run or play.

Question 7.
Iqbal has to push a lighter box and Seema has to push a similar heavier box on the same floor. Who will have to apply a larger force and why?
Answer:
Seema will experience more frictional force because heavy object will be pressed hard against the opposite surface and produces more friction.

Question 8.
Explain why sliding friction less than static friction.
Answer:
Sliding friction is always less than static friction because two sliding objects find less time to get interlocked against, each others, irregularities of surfaces so they get less friction.

Question 9.
Give examples to show that friction is both a friend and a foe.
Answer:
Friction is a friend because :

• It allows us to walk comfortably on ground.
• It allows us to grip and catch different objects.
• Things don’t move from their places because of friction.
• Speeds of moving objects can be minimized or stopped by friction only.

Friction is foe because :

• It causes wear and tear in objects of our daily use and machines we use.
• Regular maintenance of objects moving against each other (machines and tools) wastes a lot of useful money.
• It makes the movement of heavy objects very difficult.
• It does not allow the regular free movement of substances.

Question 10.
Explain why objects moving in fluids must have special shapes.
Answer:
Objects moving in fluids must have a special shape called steamlined shape. Streamlined shape is that shape which overcomes the friction of fluid. They have pointed fronts with little broader middle portion which gets tapered at the back.

Extended Learning – Activities and Projects

Question 1.
What role does friction play in the sport of your choice? Collect some pictures of that sport in action where friction is either supporting it or opposing it. Display these pictures with proper captions on the bulletin board of your classroom.
Answer:
For self attempt.

Question 2.
Imagine that friction suddenly vanishes. How would life be affected. List ten such situations.
Answer:
For self attempt.

Question 3.
Visit a shop which sells sports shoes. Observe the soles of shoes meant for various sports. Describe your observations.
Answer:
For self attempt.

Question 4.
A toy to play with :
Take an empty match box. Take out its tray. Cut a used refill of a ball pen of the same width as the tray as shown in the figure below. Fix the refill with two pins on the top of the tray as shown in Fig. Make two holes on the opposite sides of the tray. Make sure that the holes are large enough to allow a thread to pass through them easily. Take a thread about a metre long and pass it through the holes as shown. Fix beads at the two ends of the thread so that it does not come out. Insert the tray in the outer cover of the matchbox.
Suspend the match box by the thread. Leave the thread loose. The match box will start falling down due to gravity. Tighten the thread now and observe what happens.
Explain your observation. Can you relate it to friction?

Answer:
For self attempt.

HBSE 7th Class Science Friction Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is friction?
Answer:
Force acting equal and opposite to the relative motion of two objects in contact.

Question 2.
What does the friction depend upon?
Answer:
Nature of object.

Question 3.
Which surface produces more friction?
Answer:
Rough.

Question 4.
Which surface produces less friction?
Answer:
Smooth.

Question 5.
In which direction does friction work?
Answer:
Opposite to the motion.

Question 6.
What causes-friction between two surfaces?
Answer:
Irregularities of two surfaces.

Question 7.
What happens between irregularities of two surfaces in contact which produce friction?
Answer:
Irregularities get interlocked.

Question 8.
Which surface has large number of irregularities to cause friction?
Answer:
Rough surface.

Question 9.
Between flat and sliding surfaces which surface will cause less friction?
Answer:
Sliding surface.

Question 10.
What causes chalk to write on black board?
Answer:
Friction.

Question 11.
What does friction do to soles of our shoes?
Answer:
It causes wear and tear in soles.

Question 12.
What causes a matchstick to catch fire, when rubbed on rough surface?
Answer:
Friction.

Question 13.
What does friction produce?
Answer:
Heat.

Question 14.
What are things like oils, creams and grease called?
Answer:
Lubricants.

Question 15.
How are the shoes made to counter the friction and make better grip?
Answer:
They have grooves on their soles.

Question 16.
How are athletes and other sports shoes are designed to reduce friction?
Answer:
There soles have nails fixed on them.

Question 17.
What is done to the tyres of the vehicles to reduce the friction?
Answer:
They are treaded.

Question 18.
What is used in cycle brakes to increase friction?
Answer:
Brake pads.

Question 19.
What does the kabaddi players use to increase friction of their hands to grip their opponents?
Answer:
They rub their hands with soil.

Question 20.
What do we use on carrom board to reduce friction?
Answer:
Talcum powder.

Question 21.
What do we use on the hinges of the door to make door move smoothly?
Answer:
Machine oil/ Oil.

Question 22.
What is avoided between two surfaces to make movement smooth?
Answer:
Interlocking of irregularities.

Question 23.
What is used to reduce friction in machines, where lubrication are not advisable?
Answer:
Oil cushion.

Question 24.
Can we eliminate friction completely?
Answer:
No.

Question 25.
What is used to make heavy luggages move easily?
Answer:
Wheels are attached to their base.

Question 26.
Which friction is applicable when wheels are used to carry heavy weights?
Answer:
Rolling friction.

Question 27.
Among Static, Sliding and Rolling friction which is the smallest?
Answer:
Rolling friction.

Question 28.
How sliding is replaced by rolling in machines?
Answer:
By using ball bearings.

Question 29.
Name any machine, where ball bearing is used to reduce friction.
Answer:
Ceiling fan.

Question 30.
What is frictional force exerted by liquids called?
Answer:
Drag.

Question 31.
What does frictional force on an object in a fluid depend on?
Answer:
On its speed with respect to the fluid and its shape.

Question 32.
What is the special shape given to objects moving in fluid called?
Answer:
Streamlined shape.

Question 33.
Give three examples of streamlined objects.
Answer:
Ships, boats, aeroplanes.

Question 34.
How is the shape of the body of a fish which helps it in moving in water?
Answer:
It has streamlined shape.

Question 35.
When does rolling friction come in play?
Answer:
When a body rolls on other body.

Short Answer Type Questions

Question 1.
What is friction?
Answer:
Friction is a force which comes in play when two -bodies move on each other. Friction works in opposite direction to the direction of the movement of objects.

Question 2.
What causes friction?
Answer:
Friction occurs when two bodies move on each other. Each surface has some irregularities on it. When two such objects move on each other their irregularities get interlocked and friction arises.

Question 3.
How does the nature of surface effect friction?
Answer:
Nature of the surface plays major role in production of friction. The rough surface produces more friction than the smooth surface. The rough surface has more irregularities on it than the smooth surface, so more force is required to overcome the friction caused by irregularities.

Question 4.
What is a spring balance? How does it work?
Answer:
Spring balance is a device which is used to measure the force acting on a body. It consists of a coiled spring, which is attached to pointer and scale. When some object is hung with it the spring stretches and pointer points to the graduated scale to give the measurement of the force.

Question 5.
Which friction is less static friction or sliding friction? Why?
Answer:
Sliding friction is lesser than static friction, because in sliding friction the relative motion between two surfaces is less opposed by friction as the irregularities of the two surfaces in contact do not get enough time to interlock with each other which makes the motion easy.

Question 6.
What would happen, if the floor we walk on, does not produce any friction?
Answer:
If there is no friction on the floor, we would not be able to stand or walk on the floor, because it is the friction which unables us to stand or walk on the surface. The grooves of our feet or shoes get locked into the irregularities of the floor and makes us stand. If friction is not there, then we would simply slip on the floor.

Question 7.
What helps us write with a pen or pencil?
Answer:
It is the friction between the hand and pen or pencil which causes us write with pen. The grooves on our fingers make a grip on the pen’s irregularities and we are able to write.

Question 8.
Why is it difficult to move an object from its static position?
Answer:
When an object is in its static position, it has better hold of the surface on which it is placed. The irregularities of the surface are interlocked properly and more force is needed to overcome the friction offered by interlocking surfaces. So it is difficult to move the object from its position of rest.

Question 9.
Why do we rub our hands in winter when we feel cold?
Answer:
We rub our hands to make them warm, when we feel cold. Rubbing hands against each other cause friction between them. Friction produces heat, this heat makes us warm. We can feel the warmth by touching our hands on our face.

Question 10.
Why do we need to decrease friction?
Answer:
Friction is an evil which causes a lot of wear and tear in objects coming under its effects. It causes a lot of wear in machine parts which rub against each other, it erodes the surfaces and destroy their symmetries. So, we lubricate surfaces to decrease the friction.

Question 11.
How can we increase friction?
Answer:
We need to increase friction of surfaces to control the movement. Friction can be increased by increasing the irregularities of the surfaces in contact. We use spikes in the shoes of the athletes so that they can lock better in the irregularities of the ground to make better grip.

Question 12.
How can we decrease friction?
Answer:
Friction can be decreased by rolling, sliding and lubricating the surfaces in contact. We use ball bearings, wheels and lubricants like oils, grease, cream etc. to decrease the friction. Rolling, sliding and lubricating decrease the irregularities of the surfaces and make them smooth.

Question 13.
What is drag?
Answer:
Drag is the frictional force exerted by fluids. Liquids and gases are collectively called fluids. So the friction caused due to movement of objects in liquids and in air medium is called a drag.

Long Answer Type Questions

Question 1.
What is friction? How do friction arise? Explain.
Answer:
Equal and opposite force exerted by relative motion between two surfaces is called friction. Friction is always exerted in opposite direction to the force exerted. Friction acts between two surfaces. It is caused due to the movement of these two surfaces in contact. Every surface has some irregularities on it. When two surfaces come in contact, these irregularities get locked with each other. When objects are moved, the friction arises in the opposite direction of the movement.

Question 2.
What factors effect the force of friction? Explain.
Answer:
Force of friction depends upon the nature of the surfaces in contact and the force with which these two surfaces are pressed against each other. Nature of the surface on which an object moves, effects the force of friction. Rough surfaces produce more friction, while smooth surfaces produce less friction. Rough surfaces have more irregularities on them so they produce more friction. Smooth surfaces allow easy movement as they have less irregularities and the interlocking of irregularities with other surface is less as compared to the rough surfaces, so they produce less friction.

Secondly, force of friction depends upon how hardly two surfaces are pressed against each other. If two surfaces are pressed hard against each other, then the friction produced will be more.

Question 3.
How many types of frictions do you know about? Explain.
Answer:
Friction is of different types : Static friction, sliding friction and rolling friction.
Static friction is one which is produced between two surfaces in contact with each at the position of rest. This friction is more powerful than others. It is most difficult to overcome the static friction at this positions, the irregularities are most effectively pressed against each other. This type of friction needs a lot of energy to overcome.

Sliding friction: arises when two objects in contact are in motion. It is lesser than static friction. This friction is lesser because the irregularities of both surfaces do not get enough time to get locked with each other as an object is already in motion.

Rolling friction: comes in effect when two bodies are rolling on each other. Rolling movement of both objects don’t allow the locking of irregularities, thus it is the smallest friction of all they three types. Drag is the frictional force which is exerted by the fluids on the bodies moving in it. This friction needs a lot of energy to overcome so, bodies of such objects which move in fluids are streamlined to counter the friction offered by fluids.

Question 4.
What is fluid friction and on what factors does fluid friction depend?
Answer:
Friction exerted by fluids is called fluid friction. Bodies moving in air and liquids bear friction caused by air and liquid. Air and liquids are collectively called fluids. Fluid friction is also called Drag.Drag depends upon the speed of the object with respect to fluid, nature of the fluid and the shape of the object. Slow moving objects face more friction and heavy fluids offer more friction. Objects with pointed front, face less friction. All objects moving in fluids have streamlined shape so as to minimise the friction exerted by fluids.

Streamlined objects have narrow front, broader middle portion and which tapers at the back. All living organisms moving in air and water have streamlined shapes. Birds, fish etc. have streamlined body. So, Aeroplanes, boats, ships etc are designed according to birds and fish, so that they have to face less friction and has to spend less energy to overcome the friction.

Question 5.
prove with the help of an experiment that smoothness of surface reduces friction.
Answer:
Take a pencil or pen. Now put it on a table. Slightly push the pencil and see how much distance it covers, mark the point where the pencil stops after covering the distance. Now take some.cream or oil. Make a small coating of oil on the table or spread polythene on the table if possible. Now again take the pencil and put it at the same initial point. Now push the pencil slightly and let it stop on its own as done earlier. Now mark the point where the pencil stops. See the difference in the distance. In second attempt the pencil has covered more distance. This means it had to face less friction in second attempt. It proves that smoothness of the surface reduces friction.

Question 6.
Why and how do we increase friction?
Answer:
We increase friction deliberately to control the movements and motion of the objects. We also increase the friction for better grip and hold. Friction can be increased by making surfaces coarse and pressing two surfaces harder. Coarse surface has more irregularities to grip irregularities of other surface better, thus making the things come to a halt and give a better grip if object is stationary. We use brake pads in vehicles. When brake pads are pressed by pressing the lever, it gets pressed against the tyres and arrest the movement of the tyres and with this the vehicle comes to stop.

Pens are provided with ridges at the point where we hold them for writing, so that the friction between fingers and pen becomes more and a better grip can be made to write fluently. Pens without ridges get slipped out from our hands easily.

Question 7.
Why and how do we decrease friction?
Answer:
We decrease friction to save the objects from wear and tear. Friction causes wear and tear on the surfaces of the objects. It causes damage to the objects specially machines and machine parts. So, we apply a film of oil or grease between the surfaces in contact, so that it produces less friction and it causes no damage to the parts. Oils, grease etc. are called lubricants, which are used to make surfaces smooth and minimise friction. In most of the cases rolling of objects is used to reduce friction. Ball bearings are used in cycles, vehicles and machines because it reduces friction. Wheels are used to move heavy objects because wheels roll on the ground thus reducing friction and this makes the dragging of heavy objects easy. Tyres carry heavy and loaded trucks on them, as they produce less friction and need lesser energy to move them.

Friction Class 8 HBSE Notes

1. Friction is the force equal and opposite to the relative motion between two surfaces in contact.

2. Force of friction acts on both the surfaces in contact.

3. There are many factors which affect friction :

• It depends on the nature of surface.
• It depends on smoothness of surface.
• It depends on the hardness with which two surfaces in contact are pressed against each other.

4. Friction has no relation with area exposed to force of friction.

5. Friction is static, when it opposes the force applied on the body.

6. When two surfaces slide on each other, sliding friction comes into play.

7. Sliding friction is less than the static friction.

8. Friction is an evil which causes a lot of wear and tear on the surfaces of the objects due to opposite forces in action.

9. Wear and tear is more in case of static friction and less in case of sliding friction.

10. Friction is an evil but a necessary evil. No body would have been able to walk on the floor, if friction was not in play :

11. When two surfaces roll on each other the rolling friction is applied, for example in case of wheels under attache-cases. Rolling reduces the friction and movement becomes easy and smooth.

12. Fluids also exert force of friction and reduce the speed. To avoid friction due to fluid, bodies of objects moving in fluids have pointed and streamlined fronts and bodies.

13. Aeroplanes and ships etc. have streamlined bodies to overcome the friction caused by air and liquids.

Haryana State Board HBSE 8th Class Science Solutions Chapter 13 Sound Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 13 Sound

HBSE 8th Class Science Sound Textbook Questions and Answers

Question 1.
Choose the correct answer: Sound can travel through:
(a) gases only
(b) solids only
(c) liquids only
(d) solids, liquids and gases.
Answer:
(d) solids, liquids and gases.

Question 2.
Voice of which of the following is likely to have minimum frequency?
(a) Baby girl
(b) Baby boy
(c) A man
(d) A woman
Answer:
(a) Baby girl.

Question 3.
In the following statements, tick ‘T’ against those which are true and ‘F’ against those which are false :
(a) Sound cannot travel in vacuum. (T / F)
(b) The number of oscillations per second of a vibrating object is called its time period. (T / F)
(c) If the amplitude of vibration is large, sound is feeble. (T / F)
(d) For human ears, the audible range is 20 Hz to 20,000 Hz. (T / F)
(e) The lower the frequency of vibration, the higher is the pitch. (T / F)
(f) Unwanted or unpleasant sound is termed as music. (T / F)
(g) Noise pollution may cause partial hearing impairment. (T / F)
Answer:
(a) True
(b) False
(c) False
(d) True
(e) False
(f) True
(g) True.

Question 4.
Fill in the blanks with suitable words :
(a) Time taken by an object to complete one oscillation is called ________.
(b) Loudness is determined by the ________ of vibration.
(c) The unit of frequency is ________.
(d) Unwanted sound is called ________.
(e) Shrillness of a sound is determined by the ________ of vibration.
Answer:
(a) time period
(b) amplitude
(c) hertz
(d) noise
(e) frequency.

Question 5.
A pendulum oscillates 40 times in 4 seconds. Find its time period and frequency.
Answer:
Time taken by pendulum to complete 40 oscillations = 4 seconds
Time taken by pendulum
to complete 1 oscillation = \(\frac { 4 }{ 40 }\)
= \(\frac { 1 }{ 10 }\)
= 0.1 sec.
Time period of pendulum = 0.1 sec.
Frequency of pendulum
= \(\frac { 40 }{ 4 }\) \(\frac { oscillation }{ time }\)
= 10 Hz.

Question 6.
The sound from a mosquito is produced when it vibrates its wings at an average rate of 500 vibrations per second. What is the time period of the vibration?
Answer:
Time taken to complete
500 vibrations = 1 second
Time taken to complete
1 vibration = \(\frac { 1 }{ 500 }\) = 0.002
Time period of vibration = 0.002 second.

Question 7.
Identify the part which vibrates to produce sound in the following instruments:
(a) Dholak
(b) Sitar
(c) Flute.
Answer:
(a) Stretched membrane
(b) Strings
(c) air column.

Question 8.
What is the difference between noise and music? Can music become noise sometimes?
Answer:
Noise is the sound which is unpleasant for our ears. Excessive or unwanted sounds are called noise. Music is the sound which is pleasant for our ears and has soothing effect. Music sometimes can become noise when it crosses the bearable range of sound for our ears.

Question 9.
List sources of noise pollution in your surroundings.
Answer:
There are various sources which cause sound pollution in our surroundings like : Honking of horns, loud sounds of machines in factories, loud musics in parties and marriages, loud sound of T. V. or radio, loud sounds of domestic electronic appliances like mixer grinder etc. are some sources of noise in our environment.

Question 10.
Explain in what way noise pollution is harmful to humans?
Answer:

• Noise pollution can cause temporary or permanent deafening.
• It can cause many health related problems like high blood pressure
• It can cause mental illness due to lack of sleep.

Question 11.
Your parents are going to buy a house. They have been offered one on the roadside and another three lanes away from the roadside. Which house would you suggest your parents should buy? Explain your answer.
Answer:
I would suggest my parents to buy house three lanes away from the roadside because area away from the roadside have less traffic and thus less noise pollution. This would safe guard our health and peace of mind.

Question 12.
Sketch larynx and explain its function in your own words.
Answer:
Larynx is also called the voice box. As the name suggests, it causes (sound) voice in humans. It has vocal cords, which have air column vibrating in them, which cause sound in humans.

Question 13.
Lightening and thunder take place in the sky at the same time and at the same distance from us. Lightening is seen earlier and thunder is heard later. Can you explain?
Answer:
Lightening and thundering take place simultaneously but we see light earlier than thunder because light travels faster than sound, so it reaches us before the sound does.

Extended Learning – Activities and Projects

Question 1.
Visit the music room of your school. You may also visit musicians in your locality. Make a list of musical instruments. Note down the parts of these instruments that vibrate to produce sound.
Answer:
For self attempt.

Question 2.
If you play a musical instrument, bring it to the class and demostrate how you play it.
Answer:
For self attempt.

Question 3.
Prepare a list of famous Indian musicians and the instruments they play.
Answer:
For self attempt.

Question 4.
Take a long thread. Place your hands over your ears and get some one to place this thread round your head and hands. Ask her to make the thread taut and hold its ends in the hand. Now ask her to draw her finger and thumb tightly along the thread (in figure). Can you hear a rolling sound like that of a thunder ? Now repeat the activity while another friend stands near both of you. Can he hear any sound.

Answer:
For self attempt.

Question 5.
Make two toy telephones. Use them as shown in Fig. Make sure that the two srtings are taut and touch each other. Let one of you speak. Can the remaining three persons hear? See how many more friends you can engage in this way. Explain your observations.

Answer:
For self attempt.

Question 6.
Identify the sources of noise pollution in your locality. Discuss with your parents, Mends wad neighbours. Suggest how to control noise pollution. Prepare a brief report and present it in the class.
You can read more on the related topics on the following websites:
→ www.physicsclassroom .com/Class/sound/soundtoc.html
→ health.howstuffworks.com/hearing.htm
→ www.jaltarang.com for jaltarang
→ www.tempro/com/articles/hearing.html
→ www.cartage.org.lb/en/themes/sciences/ physics/mainpage.htm
Answer:
For self attempt

HBSE 7th Class Science Sound Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What produces sound?
Answer:
Vibrations in body produce sound.

Question 2.
Can sound be produced from a body which does not vibrate?
Answer:
No.

Question 3.
Why can’t we see the vibrations in most of the cases when sound is produced?
Answer:
Their amplitude is very small.

Question 4.
Name any wind musical instrument.
Answer:
Flute.

Question 5.
What is the sound producing organ in humans called?
Answer:
Larynx.

Question 6.
What is another name for larynx?
Answer:
Voice box.

Question 7.
What are the two cords stretched across the voice box called?
Answer:
Vocal cords.

Question 8.
What vibrates in larynx to produce sound?
Answer:
Vocal cords.

Question 9.
What decides the type of voice in human?
Answer:
Tightness of vocal cords.

Question 10.
How much long the vocal cords are in men?
Answer:
20 mm.

Question 11.
What is the length of vocal cords in women?
Answer:
15 mm.

Question 12.
Through which medium can sound travel?
Answer:
Solids, liquid and gaseous medium.

Question 13.
Can sound travel through vacuum?
Answer:
No.

Question 14.
Which organs in human receive sound waves? .
Answer:
Ears.

Question 15.
What is the outer stretched part of the ear called?
Answer:
Ear drum.

Question 16.
What vibrates the ear drum?
Answer:
Sound vibrations.

Question 17.
What is the to and fro motion of objects called?
Answer:
Oscillatory motion.

Question 18.
What is the frequency of oscillation?
Answer:
Number of oscillations per second is called frequency of oscillation.

Question 19.
What is the unit of frequency?
Answer:
Hertz (Hz).

Question 20.
What does a frequency of 1 Hz means?
Answer:
One oscillation in one second.

Question 21.
What are the two important properties of a sound?
Answer:
Amplitude and frequency.

Question 22.
What is the maximum distance travelled by a vibrating body on either side of its mean position called?
Answer:
Amplitude.

Question 23.
What is the time taken to complete one oscillation called?
Answer:
Time period.

Question 24.
How does amplitude effect the loudness of vibration?
Answer:
Higher the amplitude, louder is the voice.

Question 25.
Why the sound of a baby is feeble?
Answer:
Because its amplitude is small

Question 26.
What controls the shrillness of a sound?
Answer:
Frequency.

Question 27.
What is the range of audible sound for human ear?
Answer:
From 20 to 20,000 Hz.

Question 28.
What are the sounds above 20,000 ‘ Hz called?
Answer:
Ultrasound.

Question 29.
Name any use of ultrasound?
Answer:
Ultrasound is used to detect many medical problems in human.

Question 30.
What is the unpleasant and unwanted sound called?
Answer:
Noise.

Question 31.
What are the pleasant and soothing sounds called?
Answer:
Music.

Question 32.
What is the unit of loudness?
Answer:
Decibel (dB).

Question 33.
What is the loudness of a normal conversation?
Answer:
60 dB.

Question 34.
Name any ill effect of noise pollution.
Answer:
It can cause temporary deafness.

Question 35.
Write any one measure to control noise pollution.
Answer:
Planting trees along roadsides.

Short Answer Type Questions

Question 1.
How is sound produced?
Answer:
Sound is produced by the vibrating bodies. When a body vibrates it produces sound.

Question 2.
What is the importance of sound in our life?
Answer:
Our life depends on sound for every action. Sound enables us to communicate with each other. Without sound nobody would know what other communicate or wants to express.

Question 3.
What are the musical instruments?
Answer:
Musical instruments are the devices which produce various sounds which are pleasant for our ears and produce soothing effects. The sound produced by these instruments is called music.

Question 4.
How do the musical instruments produce sound?
Answer:
Musical instruments have strings the stretched membranes attached or fixed on them . Some instruments have slits to let air pass through them, the strings are plucked and membranes are struck to produce sound. On plucking or striking they start vibrating, and the whole instrument starts vibrating with them, which produces the music.

Question 5.
Describe the organ in human that produces sound.
Answer:
In humans the sound producing organ is the voice box. It is also called the larynx. In larynx there are two vocal cords stretched across, leaving a slit for the air to pass through them.

Question 6.
How does the larynx produce sound?
Answer:
Larynx has two vocal cords stretched across it. They are stretched in a way that they leave a slit for passage of air. When air is pumped in slit by the lungs, the vocal cords start vibrating, thus producing the sound.

Question 7.
What distinguishes the sounds produced by different human beings from each other?
Answer:
Vocal cords in humans are the sound producing parts. When they are vibrated they produce sound. They are held by the muscles and the tightness with which they are held determines the quality of sound. The length of the vocal cords also determines the quality of voice.

Question 8.
How is the sound propagated?
Answer:
The sound reaches from one source to another through various mediums. It always needs a medium to travel, it cannot propagate through vacuum. Sound travels through air, solid and liquid.

Question 9.
How is it possible for whales and dolphins to communicate in water?
Answer:
Whales and dolphins live under water. They produce sound to communicate with each other. As sound can travels through air, solid and liquid-all the mediums, it is travelled from one source to another in water too, so dolphins and whales can communicate.

Question 10.
How do human hear the sounds?
Answer:
Humans hear various sounds through ears. Ears have a stretched structure called eardrum. When ears receive sound, it enters down the earcanal and reach eardrum. Vibrations of sound vibrates the eardrum and it sends vibrations to inner ear from which vibrations are sent to brain for interpretation of sound.

Question 11.
Why is it advised, not to put a sharp or pointed thing in our ear?
Answer:
It is advised not to put sharp or pointed things in the ear because it can damage the eardrum. Eardrum is a stretched membrane which is delicate. If the sharp or pointed thing would touch the eardrum, it would damage the eardrum and cause deafness.

Question 12.
What is oscillatory motion?
Answer:
The to and fro motion of the object is called vibration. This motion is the movement in both direction from its mean position- This motion in either side of the object from its mean position is called the oscillatory motion.

Question 13.
What is frequency of a motion?
Answer:
The number of to and for movement or number of oscillations per second is called the frequency of a motion. Frequency is expressed in Hertz. It is symbolized as Hz.

Question 14.
How does frequency effect the quality of sound?
Answer:
The frequency determines the shrillness of the sound. Shrillness is also called the pitch of sound. The pitch of the sound is higher if it has high frequency and the pitch is low if the frequency is less.

Question 15.
What controls the quality of voice in humans?
Answer:
Amplitude and frequency of vibrations control voice in human beings. If amplitude is high the loudness of sound will also be high, if frequency is high the shrillness or pitch will be high in voice.

Question 16.
Describe the properties of voice in men.
Answer:
Men have high amplitude of vibrations so their voice is loud and they have low frequency so-they have less shrillness in their voice.

Question 17.
Describe the properties of voice in women.
Answer:
Women have high frequency of sound waves, so they have high pitched voice it means they have high shrillness in their voice. On the other hand they have low amplitude so they have less loudness in their voice.

Question 18.
Describe the audible range of fequencies for human beings.
Answer:
Human beings cannot hear sounds below 20 Hz that means sounds with less than 20 vibrations per second cannot be heard by human beings. On the other hand sounds with frequency more than 20 KHZ also cannot be heard by human beings. 20 KHz means 20,000 vibrations per second. Therefore, roughly the audible range of sounds for human beings vary between 20 Hz to 20 KHz.

Question 19.
What are ultrasounds? How are they useful to us?
Answer:
Sounds with frequency of above than 20 KHz are called ultrasound. Ultrasounds cannot be heard by human beings, but they are very useful for human beings. Ultrasounds are used in field of medicine to detect the disorders inside the body of human beings. They are also useful in industries. They are used to detect the flaws and cracks in metallic structures.

Question 20.
What is noise?
Answer:
Noise is the unwanted and unpleasant sounds reaching our ears. They cause disturbance and are harmful. Noise is the sound which crosses the limit of audible loudness for us. Normally sounds at 80 dB of loudness becomes painful to bear and is called noise.

Question 21.
Give any five sources of noise in your surroundings.
Answer:
Five sources of noise in our environment are :

• Noise made by traffic.
• Noise created by electrical appliances used at home like coolers, mixer grinder etc.
• Loud sounds of T.V., Radio etc.
• Noise created by loud music in marriages and religious functions.
• Noise created by construction works in neighbourhood.

Question 22.
What do you mean by hearing impairment? How is it caused?
Answer:
Hearing impairment means disability to hear. It is caused by diseases of ear, injury of ear or due to degeneration of hearing mechanism with growing age. Hearing impairment can be overcome by using hearing aids if impairment is not permanent.

Question 23.
How can hearing impairment be overcome or avoided?
Answer:
Hearing impairment can be avoided by avoiding noise or avoiding the usage of sharp of pointed objects inside ear, We should avoid any ear injury. In case of hearing impairment which is temporary hearing aids help in overcoming it or using other aids like sign language etc.

Question 24.
What is noise pollution?
Answer:
Presence of excessive or unwanted sounds in the environment, which cause discomfort for us is called noise pollution. Excessive sounds are produced by honking of horns, loud speakers, crackers, machines etc.

Question 25.
How can noise pollution be controlled?
Answer:
Noise pollution can be controlled by controlling their sources. Blowing of horns should be avoided in residential areas, near schools or hospitals. Using loudspeakers etc. should also be avoided in these areas. T.V., radio etc should be played at low volume. Trees should be planted along the roadside to create a buffer zone to absorb excessive sounds on roads.

Long Answer Type Questions

Question 1.
How is sound produced? How does it travel from one place to another?
Answer:
Sound is produced by the vibrations of the body. Only vibrating bodies produce sound. Those bodies which produce vibrations produce sound but when they stop vibrating they also stop producing sound.
Sound reaches from one source to another. It travels from one point to another through some medium. Sound waves can travel through air, liquid and even through solids. What we hear one another, that sound travels through air medium. But we can bear some body talking in next room too, that means sound waves have crossed wall to reach us. Dolphins and whales communicate in water.

Question 2.
Explain hew many types of musical instruments are there? Hew die they make sound?
Answer:
Musical instruments are differentiated on the basis of their vibrating parts, Some musical instruments have sretched membranes Which produce vibrations to make sound. Second type of musical instruments have stretched strings, which vibrate to produce sound. In third v type of instruments the wind column is used to ’ produce sound.

Instruments like hands, drums, mridangam etc, have stretched leather membrane which is struck with hands or stick to produce sounds. In instruments like guitar, sitar, veena, violin etc,, strings are struck with fingers or rubber with other instruments produce musical sounds. Instruments like mouth-organ, sehnai, flute etc, use air column to produce sounds.

Question 3.
What is nuisa? Haw is noise pollution created?
Answer:
Noise is the unwanted and unpleasant sounds around us in our environment. When these noises become huge, it creates noise pollution. Different, loud and shrill sounds discharged in environment cause noise pollution. Honking horns of vehicles on road, loud music of T-Vs and Radios, loud music in marriages and parties, noise of machines in factories, domestic electrical appliances like mixer grinder, construction work in neighbourhood, etc. are the ‘ various sources of noise polluiton in our environment.

Question 4.
What are the ill-effects of noise pollution? How can we control noise pollution?
Answer:
Noise pollution has many bad effects on our body and health. Our health and mental peace are adversely affected by noise pollution. Noise pollution becomes the root cause of many mental disorders like anxiety, depression etc. Besides mental disorders, physical disorders like hypertension, skin diseases, lack of sleep etc. are also caused by noise pollution. It is more harmfid for students and sick people.

For controlling noise pollution, honking of horns from vehicles should he banned near residential areas, schools and hospitals. T.Vs. and Radios should be played at low volume. Loudspeakers should not be allowed during sleeping hours. Trees and plants should be extensively planted along the road sides to create a buffer zone. Trees absorb noise and help in controlling noise pollution.

Sound Class 8 HBSE Notes

1. We hear different sounds in our daily life.

2. Sound is produced by the vibrating bodies. Only vibration can produce sound. Vibrations are to and fro movements of any object and this to and fro movements produce different sounds we have.

3. When the vibrations start, we hear sound, but when vibrations stop, the sound is not heard anymore.

4. Different musical instruments produce sound only due to the vibrations made by them, when they are beaten or plucked by us.

5. It is not only the vibrations of the strings or the stretched membranes of the musical instruments that produce sound, but it is the vibration of the whole instruments that produce sound.

6. In human beings it is the vibrations of the voice box or the larynx that causes the sound. Air passing through the vocal cords attached to larynx cause vibrations of the vocal cords, which enables us to produce sound.

7. It is the tightness of the vocal cords that make sounds different from each other in different human beings. The length of the vocal cords are different in men, women and children, so their voice is also different from each other.

8. Sound cannot pass from one source to another in vacuum. Sound needs medium to travel. Air, liquid, solid are the medium through which sound can travel from one source to another.

9. In human beings sound is produced by voice box, and received by hearing organs-ears. Receiving sound is called hearing. Our ear is so designed that it receives the vibrations and interpret it as sound.

10. The maximum distance a vibrating body travels from its means position is called amplitude of vibration.

11. The time taken to complete one oscillation (to and fro movement) is called the time period.

12. The number of oscillation per second is called the frequency of vibration. Frequency is expressed in Hertz (Hz).

13. Higher the frequency of vibration, higher is the pitch or shrilners of the sound.

14. High amplitude of vibration produces loud sound.

15. Unpleasant or unwanted sounds are called noises.

Haryana State Board HBSE 8th Class Science Solutions Chapter 6 Combustion and Flame Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 6 Combustion and Flame

HBSE 8th Class Science Combustion and Flame Textbook Questions and Answers

Question 1.
List conditions under which combustion can take place.
Answer:
Following conditions are necessary for combustion:
(i) The substance should be combustible.
(ii) It should have low ignition temperature.
(iii) There should be proper supply of air.

Question 2.
Fill in the blanks:
(a) Burning of wood and coal causes …………. of air.
(b) A liquid fuel, used in homes is …………. .
(c) Fuel must be heated to its before it …………. starts burning.
(d) Fire produced by oil cannot be controlled by …………. .
Answer:
(a) pollution
(b) Kerosene
(c) ignition temperature
(d) water.

Question 3.
Explain how the use of CNG in automobiles has reduced pollution in our cities.
Answer:
CNG has replaced petrol and diesel as fuel in automobiles because petrol and diesel produced a lot of unbumt carbon particles and emitted carbondioxide and nitrogen oxides and sulphur dioxide. These all gases are poisonous gases and cause various environmental hazards. But CNG is safe because it produces these substances in very small amounts thus reducing pollution in cities.

Question 4.
Compare LPG and wood as fuels.
Answer:

Question 5.
Give reasons:
(a) Water is not used to control the fire involving electrical equipment.
(b) LPG is a better domestic fuel than wood.
(c) Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not. .
Answer:
(a) Water is a conductor of electricity, so it can easily conduct electric current and causes danger of electric shocks.
(b) LPG is a better domestic fuel than wood because unlike wood it does not produce smoke and is comparatively easy to transport.
(c) Paper by itself catches fire easily because it has low ignition temperature but when wrapped around an aluminium pipe its

Question 6.
Make a labelled diagram of a candle flame.
Answer:

Different Zones of Candle flame

Observe the foaming reaction. What happens to the candles? Why? In what order?

Answer:
The candles get extinguished. The smaller candle with get extinguisher first because thfe supply of oxygen is cut of due to foam; The smaller candle will come in effect of foam earlier than the longer one and thus stop burning prior to the longer candle.

Activity

Combustible and Non-combustible Substances

HBSE 8th Class Science Combustion and Flame Important Questions and Answers

Very Short Answer Type Questions

Question 1.
Why do we need fuel?
Answer:
We need fuel to generate energy.

Question 2.
Name any three fuels.
Answer:
Coal, wood, LPG, kerosene, petrol.

Question 3.
What is produced during combustion?
Answer:
Heat and light.

Question 4.
In what forms light is given during combustion?
Answer:
In form of flame or glow.

Question 5.
How does charcoal burn?
Answer:
It burns with glow.

Question 6.
How does a candle burn?
Answer:
It burns with flame.

Question 7.
Name two objects which burn without flame.
Answer:
Coal and charcoal.

Question 8.
Name two objects which burn with flame.
Answer:
LPG and candle.

Question 9.
Name any three combustible substances.
Answer:
Wood, coal, LPG.

Question 10.
What is necessary for substances to burn?
Answer:
Air.

Question 11.
How does sun produces heat although it does not have air?
Answer:
It produces heat by nuclear reactions.

Question 12.
In addition to air, what else is a necessary condition for a substance to burn?
Answer:
Low ignition temperature.

Question 13.
What are the substances with very low ignition temperature called?
Answer:
Inflammable substances.

Question 14.
Name some inflammable substances.
Answer:
Alcohol, petrol, LPG., etc.

Question 15.
What substances are used to extinguish fire?
Answer:
Water, sand, fire extinguishers.

Question 16.
What should we use to extinguish fire in case of electric short circuit?
Answer:
Sand or soil.

Question 17.
Name different types of fire extinguishers.
Answer:
(i) Soda-acid fire extinguishers
(ii) Hydrocarbon fire extinguisher.

Question 18.
Name different types of combustions.
Answer:
Rapid combustion, Spontaneous combustion and explosions.

Question 19.
Name different zones of a flame.
Answer:
Outer non-luminous zone, luminous zone and dark zone.

Question 20.
Which zone of a flame has highest temperature?
Answer:
Non-luminous zone.

Question 21.
Name two properties of an ideal fuel.
Answer:
High calorific value and low cost.

Question 22.
Is there any ideal fuel?
Answer:
No ideal fuel exist.

Question 23.
What is smoke?
Answer:
Smoke is unburnt carbon particles.

Question 24.
Which diseases do incomplete combustion cause?
Answer:
Respiratory and skin diseases.

Question 25.
What is supposed to be the cause of global warming?
Answer:
Increasing amount of carbon dioxide.

Question 26.
What is the rise in temperature of the environment of earth called?
Answer:
Global warming.

Question 27.
What does global warming lead to?
Answer:
Global warming leads to melting of polar glaciers.

Question 28.
Which chemicals give rise to acid rains?
Answer:
Sulphur dioxide and nitrogen oxides.

Question 29.
Which fuel is being used in automobiles in place of petrol and diesel?
Answer:
CNG.

Question 30.
Does CNG produce poisonous substances on burning?
Answer:
In very small amounts.

Short Answer Type Questions

Question 1.
Define combustion.
Answer:
A chemical process in which a substance reacts with oxygen to give off heat is called combustion. Burning of substances to get heat is called combustion.

Question 2.
What is produced when a combustible substance burns?
Answer:
When a combustible substance burns it produces heat and light. Light is in the form of glow or flame. Some combustible substances do not
burn in a flame, they simply glow.

Question 3.
How will you prove that air is necessary for burning?
Answer:
Burn a candle. Now put a beaker inverted on it. You will see the flame will flicker and then it will extinguish. As the inverted beaker has cut off the oxygen supply, the flame is extinguished. This proves air is necessary for burning.

Question 4.
What do you mean by ignition temperature?
Answer:
The lowest temperature at which a substance catches fire is called its ignition temperature. This is the temperature which has to be there, if the substance has to burn, below it the object will not catch fire.

Question 5.
What are inflammable substances?
Answer:
Some substances have very low ignition temperature and they catch fire very easily. Suflj substances are called inflammable substances. Petrol, alcohol, LPG etc. are the inflammable substances.

Question 6.
Write three things necessary for fire to produce?
Answer:
Three conditions necessary to produce fire are following:
(i) Presence of oxygen i.e, air.
(ii) Ignition temperature.
(iii) Presence of combustible substances.

Question 7.
What can be done to put the fire off?
Answer:
To put off the fire one of the conditions necessary for burning should be removed or controlled. If we cut off the supply of air, fire will be extinguished or we can bring the ignition temperature down to blow off the fire.

Question 8.
Why can’t water control the fire due to oils?
Answer:
Water cannot put off fire due to oils because water is lighter than oil. It settles down the oil particles and cannot bring the ignition temperature of the substance down, thus cannot control the fire.

Question 9.
What should be done to control fire due to oils?
Answer:
In case of fire due to oils, water is not useful as it is lighter than oil and settles down below the oil particles. In such cases, sand or soil should be used. They cut off the supply of air to the fire and it is put off.

Question 10.
How does carbondioxide help in putting off fire?
Answer:
Carbondioxide covers the surface of the burning substance and does not allow the oxygen to reach the substance. In absence of oxygen the fire gets put off.

Question 11.
What is rapid combustion?
Answer:
When gases bum quickly to produce heat and light it is called rapid combustion. This process takes place rapidly and takes less time.

Question 12.
What is spontaneous combustion?
Answer:
When an object catches fire on its own without any apparant cause, it is called spontaneous combustion. In this type of combustion the object suddenly bursts into flame. For example, phosphorus catches fire in air.

Question 13.
Write the properties of an ideal fuel.
Answer:
An ideal fuel has following qualities:
(i) It has high calorific value.
(ii) It has low ignition temperature.
(iii) It is cheap and easily available.
(iv) It can be easily transported.

Question 14.
Write some harmful effects of burning fuel.
Answer:
Burning fuel can cause following ill effects:
(i) Unbumt carbon particles of these fuels can cause respiratory and skin diseases.
(ii) Smoke emitted by these fuels cause pollution and many diseases.
(iii) Poisonous gases like carbondioxide, carbonmonoxide and sulphurdioxide etc. pollute the air.

Long Answer Type Questions

Question 1.
Explain the conditions necessary for cpmbustion.
Answer:
Combustion is burning of substances. For combustion of substances following conditions are necessary: .
(i) Air:
Substances only bum in sufficient supply of air i.e. oxygen. If the supply of air is hindered the object will not bum. In case of a burning object, if air is hindered, it will stop burning. This fact is used in extinguishing the fires.

(ii) Ignition Temperature:
Ignition temperature is the minimum temperature at which a substance starts burning. Those substances which have low ignition temperature can bum easily, while those which have high ignition temperature need more heating and burn late.

(iii) Presence of combustible substance:
If a substance is not combustible, it will not catch fire at all, so to produce fire it is necessary to have a combustible substance.

Question 2.
Describe the working of soda-acid fire extinguisher.
Answer:
Soda-acid fire extinguisher is based on the cooling the temperature of the burning object. This type of fire extinguisher contains sulphuric acid and sodium bicarbonate. When the extinguisher becomes functional, the sulphuric acid reacts with sodium bicarbonate to produce carbondioxide. Carbondioxide when released, cuts off the supply of oxygen and water is released to bring down the ignition temperature of the burning object. In this way fire is controlled.

Question 3.
What are different types of combustion?
Answer:
Combustion is of three types:
(i) Rapid combustion: When gases bum rapidly to produce heat and light it is called rapid combustion.
(ii) Spontaneous combustion: When any material like phosphorus bums on its own without any apparant cause, it is called spontaneous combustion.

(iii) Explosion:
When combustion takes place with sudden release of heat and light and a large amount of gas in form of bang, it is called explosion as in case of crackers and bombs.

Question 4.
Explain various harmful effects of burning fuels.
Answer:
Fuels are very useful for us. But there are certain disadvantages of burning fuels.
(i) Fuels like wood, coal, petroleum etc. which are carbon fuels generally release unbumt carbon particles which are quite harmful. They cause various respiratory and skin diseases.

(ii) In most of the cases carbondioxide is released during burning of fuels. This carbondioxide is released in environment. Carbondioxide is an identified cause of increasing temperature of the earth, which is called global warming.

(iii) Incomplete combustion of fuels release many poisonous gases like carbonmonoxide. in the environment. These poisonous gases create air pollution, such air if inhaled can be fatal.

(iv) Combustion of coal and diesel generates sulphurdioxide. It is a corrosive gas and it causes suffocation.

(v) Burning of petrol releases nitrogen oxides. These oxides of nitrogen and sulphurdioxide combine with rain water to cause acid rains.

Question 5.
Describe the various zones of a candle flame.
Answer:
The candle flame has three different zones. These zones can be distinguished on the basis of their colour.
(i) The outer zone:
It is blue in colour and it has very high temperature. It is the hottest zone of the flame. In this zones the wax vapours bum completely due to availability of enough oxygen, in turn carbondioxide and water vapours are produced.

(ii) The middle zone:
In this zone the flame bums with yellow colour and the wax vapours start burning here. The yellowish colour of the flame is due to the burning of carbon particles. These carbon particles are produced due te incomplete burning of the wax vapours due to less suppy of oxygen. Carbonmonoxide is also produced along the carbon particles. This zone is luminious but with low temperature.

(iii) The inner zone:
This zone appears black in colour as no combustion of wax vapour take place in this zone due to no supply of oxygen in this zone. It is the coolest zone of the flame having unbumt wax vapour.

Combustion and Flame Class 8 HBSE Notes

1. All substances which catch fire/bum in air are called combustible substances.
2. Wood, paper, petrol, L.P.G., charcoal etc. are some examples of combustible substances.
3. During combustion heat and light is emitted. The light is emitted in the form of flame.
4. All combustible substances do not burn with flame, for example coal does not bum with flame, while wood, paper, candle, L.P.G., etc. bum with a flame.
5. There are two main things required by a substance to become combustible. These are: low ignition temperature and air.
6. Ignition temperature is the lowest temperature at which a combustible substance can easily catch fire. Inflammable substances have very low ignition temperature.
7. If any of the above condition is removed,’fire can be extinguished. Either we bring ignition temperature below minimum or we cut off the supply of air.
8. Water, sand are mostly used to bring fire under control.
9. There are three main zones of a flame. The outermost zone has the highest temperature while the inner zone has unbumt carbon particles.
10. Fuel is a substance which is used to give energy and heat. Ideal fuel has low ignition temperature and readily available. It is cheap and has high calorific value. It is free from pollution.
11. But no fuel is an ideal fuel.
12. Fuels are not same in their efficiency and cost.
13. Calorific value of fuels is expressed in units of kilojouls per kg.
14. Combustion of an inflammable substance should be complete because incomplete combustion produce unburnt carbon particle which can cause serious environmental hazards like acid rain, global warming and poisonous gases causing dangerous diseases in living beings.
15. Global warming the most alarming environmental problem is being created due to increased amount of carbondioxide in air.
16. Acidic rain is caused due to the oxides of nitrogen and sulphur released in environment due to burning of coal, diesel and petrol.

Haryana State Board HBSE 8th Class Science Solutions Chapter 5 Coal and Petroleum Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 5 Coal and Petroleum

HBSE 8th Class Science Coal and Petroleum Textbook Questions and Answers

Question 1.
What are the advantages of using GNG and LPG as fuels?
Answer:
CNG – Compressed Natural Gas and LPG – Liquefied Petroleum Gas are easy to handle and use. It is easy to transport them and moreover they are free from any types of pollution on usage.

Question 2.
Name the petroleum product used for surfacing of roads?
Answer:
Bitumen or coaltar is used for surfacing of roads.

Question 3.
Describe how coal is formed from dead vegetation. What is this process called?
Answer:
Millions of years ago many dead animals and plants got trapped under the layers of earth. They got compressed and the temperature under the earth started raising due to hfgh pressure and temperature, the dead plants and animals got converted into coal. This process is called carbonization.

Question 4.
Fill in the blanks:
(а) Fossil fuels are ………. , …………. and …………. .
(b) On destructive distillation of coal …………. , …………. and …………. are obtained.
(c) Process of separation of different constituents from petroleum is called …………. .
(d) Least polluting fuel for vehicle is …………. .
Answer:
(a) coal, petroleum and natural gas
(b) coke, coal-tar and coal gas
(c) refining
(d) CNG.

Question 5.
Tick True/Ffdse against the following statements:
(а) Fossil fuels can be made in the laboratory. (T/F)
(b) CNG is more polluting fuel than petrol. (T/F)
(c) Coke is almost pure form of carbon. (T/F)
(d) Coal-tar is a mixture of various substances. (T/F)
(e) Kerosene is not a fossil fuel. (T/F)
Answer:
(a) False
(b) False
(c) True
(d) True
(e) False.

Question 6.
Explain why fossil fuels are exhaustible natural resources?
Answer:
Fossil fuels are exhaustible natural resources because they are made by the decomposition of the dead remains of living organisms. It is present in limited quantity beneath the earth, thus it will come to an end by human usage.

Question 7.
Describe characteristics and uses of coke.
Answer:
Coke is obtained by burning of coal in absence of oxygen. The process is called destructive distillation. Coke is used to manufacture steel. Coke is used in the extraction of many metals.

Question 8.
Explain the process of formation of petroleum.
Answer:
Petroleum is a fossil fuel. It is formed beneath the earth by decomposition of the dead bodies of the living organisms hurried beneath the earth. Due to some natural calamities like earthquake or volcano, innumerable living organisms (Plants and animals) got hurried beneath the earth. Due to heat and pressure, they started getting decomposed and got converted into liquid and gas form. In this way Petroleum oil and petroleum gas are formed.

Question 9.
The following Table shows the total power shortage in India from 1991-1997. Show the data in the form of a graph. Plot shortage percentage for the year on the Y- axis and the year on the X-axis.

Answer:

Extended Learning – Activities And Projects

Get an outline map of India. Mark the places in the map where coal, petroleum and natural gas are found. Show the places where petroleum refineries are situated.
Answer:
For self attempt.

2. Choose any five families of your neighbourhood. Enquire whether their energy consumption (coal, gas, electricity, petrol, kerosene) has increased or decreased in the last five years. Enquire also about the measures they adopt to conserve energy.
Answer:
For self attempt.

3. Find out the location of major thermal power plants in India. What could be the reasonsi for their being located at those places?
For more information visit:

• www.energyquest.ca.gov/story/chapter08.html
• en.wikipedia.org/ wiki/ Non-renewable_resources
• http://www.eiadoe.gov/kids/energyfacts/ sources/non-renewable/oil.html

Answer:
For self attempt.

HBSE 8th Class Science Coal and Petroleum Important Questions and Answers

Very Short Answer Type Questions

Question 1.
From where we find all the materials we use in our daily life?
Answer:
We get all these materials from natural resources as well as from man-made resources.

Question 2.
How many kinds of natural resources are there on the basis of availability of materials?
Answer:
On the basis of availability of materials, natural resources are oftwo types: Inexhaustible and exhaustible.

Question 3.
What are inexhaustible natural resources?
Answer:
Inexhaustible natural resources are those resources which cannot be finished by human activities.

Question 4.
Give two examples Pf Inexhaustible natural resources.
Answer:
Sunlight and air.

Question 5.
What are exhaustible natural resources?
Answer:
Exhaustible natural resources are those resources which are present in limited quantity and can get finished by hurt!an activities.

Question 6.
Give two examples of exhaustible natural resources.
Answer:
Petroleum, wildlife.

Question 7.
What are fossil fuels?
Answer:
Those fuels which got formed by the decomposition of the dead remains of living organisms for a long period of time are called fossil fuels.

Question 8.
Give tWo examples .of fossil fuel.
Answer:
Petroleum, coal.

Question 9.
What is coal?
Answer:
Coal is an exhaustible natural fossil fuel which is as hard as stone and is of black colour.

Question 10.
Write any two uses of coal.
Answer:
Coal is used as fuel to cook food. Coal is used as fuel to run trains.

Question 11.
What does coal mainly consist of?
Answer:
Coal mainly consists of carbon.

Question 12.
What is cabonization?
Answer:
Slow process of conversion of dead remains of living organisms into coal is called carbonization.

Question 13.
Which gas is released when coal ishumt?
Answer:
Carbondioxide.

Question 14.
To which process coal is put to get some useful products?
Answer:
Destructive distillation.

Question 15.
What is destructive distillation?
Answer:
Burning of coal in absence of oxygen to get coke and; other useful products is called destructive distillation.

Question 16.
What is the pure form of carbon?
Answer:
Coke.

Question 17.
What is coal-tar?
Answer:
Coal-tar is a black liquid that is produced during destructive distillation of coal.

Question 18.
Which petroleum product is used for metalling the roads in place of coal-tar?
Answer:
Bitumen.

Question 19.
What is used as fuel in light vehicles?
Answer:
Petrol.

Question 20.
What is used as fuel in heavy vehicles?
Answer:
Diesel.

Question 21.
Where was petroleum formed?
Answer:
Petroleum was formed under the sea.

Question 22.
Which conditions under the sea formed petroleum?
Answer:
Absence of air, high temperature and high pressure.

Question 23.
Where was the first oil well digged?
Answer:
Pennsylvania, U.S.A. in year 1859.

Question 24.
Name some places of India where oil is found.
Answer:
Assam, Gujarat, Bombay High, River basins of Godawari and Kaveri.

Question 25.
Which constituents are separated from-petroleum during its refining?
Answer:
Petroleum gas, petrol, diesel, lubricating oil, paraffin wax etc.

Question 26.
What is the full form of L.P.G.?
Answer:
Liquefied Petroleum Gas,

Question 27.
What is the use of L.P.G.?
Answer:
L.P.G. is used as fuel in home and in vehicles.

Question 28.
What is the use of Paraffin wax?
Answer:
Used in ointments, candles, vaseline, etc.

Question 29.
What are petrochemicals?
Answer:
Various useful constituents obtained from petroleum are called petrochemicals.

Question 30.
What is full form of C.N.G.?
Answer:
Compressed Natural Gas.

Question 31.
What are the uses of C.N.G.?
Answer:
C.N.G. is used as pollution free fuel for vehicles and in power generation.

Question 32.
Where in India is C.N.G. found?
Answer:
Tripura, Jaisalmer, Offshore of Mumbai and in Krishna Godawari Delta.

Question 33.
Can coal, petroleum and natural gas be prepared in laboratory?
Answer:
No.

Short Answer Type Questions

Question 1.
In how many types can we classify our resources?
Answer:
We can classify out natural resources in two types:
(i) Man-made resources
(ii) Natural resources.
Natural resources can further be classified in two types on the basis of the availability of resources: Exhaustible and inexhaustible resources.

Question 2.
What do you mean by Inexhaustible natural resources?
Answer:
These are the resources which are present in nature in unlimited amount and can never get finished by human activities. Air, sunlight, soil etc. are examples of inexhaustible natural resources.

Question 3.
What do you mean by exhaustible natural resources?
Answer:
Exhaustible natural resources are those resources which are present in nature in limited amounts and can get finished by human activities. Petroleum, Natural Gas, Coal etc. are exhaustible natural resources.

Question 4.
What do you mean by fossil fuels?
Answer:
Fuels which were formed by the dead remains of the living organisms by process which took thousands of year to complete are called fossil fuels. Petroleum, coal, natural gas are the fossil fuels which got formed under the sea and earth respectively, when they got hurried under the sea and earth.

Question 5.
What is coal and write its uses?
Answer:
Coal is a black stone like substance. It is formed by the dead remains of the living organisms.
(i) Coal is used as fuel to cook food.
(ii) It is used to run trains, as it is burnt to generate steam in engine.
(iii) It is used in thermal power plants to produce electricity.
(iv) Coal is also used as fuel in different industries.

Question 6.
How was coal formed?
Answer:
Millions of years ago dense forests of earth got hurried under the soil due to volcanoes and earthquakes. More deposits of soil compressed the hurried dead bodies. As they became deeper temperature started rising. This started converting dead bodies into coal.

Question 7.
What is coke? How is it useful to us?
Answer:
Coke is a hard porous black substance. It is obtained by destructive distillation of coke. It is almost pure form of carbon.
(i) Coke is used to manufacture steel.
(ii) It is used in extraction of many metals.

Question 8.
What is coal-tar? How is it useful to us?
Answer:
Black liquid obtained during destructive distillation of coal is coal-tar. It is thick and smells unpleasant. It is a mixture of hundreds of substances. Substances obtained from coal-tar are used to manufacture synthetic dyes, drugs, explosives, perfumes, plastics, paints, roofing materials, photographic materials, etc.

Question 9.
What do you mean by petroleum?
Answer:
Petroleum is a fossil fuel obtained from the dead remains of organisms living in sea. Petroleum is a dark oily liquid having unpleasant . odour. It has various useful constituents which are separated from it by process of fractional distillation at petroleum refineries.

Question 10.
How was petroleum lormed?
Answer:
Millions of years ago, sea organisms died and their dead bodies got settled at the bottom of the sea. Slowly they got covered by sand and clay. Absence of air, high temperature and high pressure for years, converted these bodies into petroleum oil and natural gas.

Question 11.
Name any three constituents obtained from refining petroleum and their uses.
Answer:
(i) L.P.G.: It is used as domestic fuel and fuel for vehicles.
(ii) Petrol: It is used as fuel for light vehicles, aviation fuel and used in drycleaning of fabric.
(iii) Kerosene: It is used as fuel for stoves, lamps an d for jet aircrafts.

Question 12.
What is diesel? How is it different from petrol?
Answer:
Diesel is one of the constituents obtained by the refining or fractional distillation of petroleum. It is mainly used as the fuel for vehicles as petrol is used. But it is different from petrol, as it is used as fuel for heavy vehicles like trucks, lories, etc. while petrol is used as fuel in light vehicles like cars, scooters, etc.

Question 13.
What is CNG?
Answer:
GNG is Compressed Natural Gas which is a fossil fuel and is formed along petroleum oil. It is used as the pollution free fuel for transport vehicles. It is more convinient to use as its transportation is easy and it can be directly burnt.

Long Answer Type Questions

Question 1.
Classify various materials we use in our lives.
Answer:
All the materials we use can be broadly classified into two groups:
(a) Natural Resources
(b) Man-made Resources.
(a) Natural resources are those resources which are present in our nature, gifted by God. They can be freely used. Soil, air, sunlight, water, wildlife, etc. are some natural resources.
(b) Man-made resources are those resources which are formed by various efforts of man and are artificial. Plastics, fibres, electricity, etc. are all artificial resources.

On availability of materials natural materials can further be classified as:
(i) Inexhaustible Natural Resources:
Those resources which are present in unlimited quantity and will never get exhausted by human activities. Sunlight, air, soil, etc. are some inexhaustible natural resources.

(ii) Exhaustible Natural Resources:
Those resources which are available in limited amount and will get finished by human activities. Petroleum, coal, wildlife, forests, etc. are some examples of exhaustible natural resources.

Question 2.
What is coal and how was it formed? Explain.
Answer:
Coal is a fossil fuel which is as hard as a stone. It is black in colour and is mainly used as fuel. As coal is a fossil fuel, it was formed by the dead remains of the plants. Millions of years ago vegetation in forests got trapped under soil layers due to earthquakes and volcanic erruptions. More soil layers got deposited on it and it went deeper and deeper beneath the earth.

This raised the temperature and pressure beneath the soil. This initiated the process of burning these dead remains. Slowly all the vegetations got converted into coal which is a rich form of carbon. This whole process is also called carbonization.

Question 3.
How was petroleum formed? What is refining of petroleum?
Answer:
Petroleum is a fossil fuel which got formed by the dead remains of the sea-animals. These animals slowly got trapped under soil and clay and more deposits were formed with time. Due to depth, the temperature and pressure raised and over the years they got converted into petroleum oil. Since oil is lighter than water, it did not get mix with water and got raised to the superficial rocks, which did not allow it to pass through them. To obtain petroleum, we have to dig wells to perforate the top rocks and pump up the petroleum oil.

The petroleum oil we get from these wells is a mixture of variuos other useful substances. Petroleum oil is, thus, refined to separate these useful by-products in petroleum refineries.

Question 4.
Name different constituents of petroleum and write their uses.
Answer:
Following are various constituents of petroleum oil obtained during fractional distillation in oil refineries:
(i) Liquefied Petroleum Gas (L.P.G.): It is primarily used as domestic fuel. Now it is used as fuel in vehicles and industry.
(ii) Petrol: It is a black liquid used as fuel in light vehicles like scooters, cars, etc. It is also used as aviation fuel and used for dry cleaning of fabrics.
(iii) Kerosene: It is used as fuel in stoves, lamps and jet aircrafts.
(iv) Diesel: It is used as fuel for heavy vehicles and in electric generators.
(v) Lubricating oil: It, is used to lubricate metal parts and machines.
(vi) Paraffin wax: It is used in ointments’, vaselines and in candles.
(vii) Bitumen: It is used in paints and is used in road-surfacing in place of coal-tar.

Question 5.
Write a note on Natural Gas.
Answer:
Natural gas is one of the most important forms of fossil fuel. The reason being that it is very easy to transport through pipes and cylinders. Natural gas is extracted and stored under very high pressure. As it is kept compressed under high pressure, it is called .

Compressed Natural Gas or CNG. The great advantage of CNG is that it does not cause pollution on usage as in case of other petrochemicals like petrol and diesel. Secondly, it can be directly burnt in homes and factories for cooking and other purposes. Natural gas is also used as the fuel for many manufacturing units of chemicals and fertilizers.

Question 6.
Why is it necessary to use coal and petroleum economically?
Answer:
There are two main reasons for which economical use of fossil fuels is necessary.
(i) Fossil fuels are exhaustible sources. If they are used indiscriminately, they will be exhausted, as they are present in nature in limited amount. It takes millions of years to form fossil fuels, so it is not possible to make new fossil fuels artificially.

(ii) Secondly, fossil fuels specially coke, petrol, diesel, etc. generate polluting gases on burning. Coke is almost carbon and produces carbondioxide on binning, whieh pollutes our environment. These polluting emissions have given rise to dangers of global warming and air pollution. So, their limited and economic use can control pollution and give better environment to live in.

Question 7.
Write some ways in which we can conserve fossil fuels.
Answer:
Economic and controlled consumption of fossil fuel can help conserving our natural resources. Following ways and measures can conserve owr resources:
(i) Vehicles shcaiM be driven at eeaastant and moderate speed.
(ii) Engines should he switched off at traffic lights or other temporary halts.
(iii) Proper and regular maintenance of vehicles.
(iv) Vehicle pooling can reduce number of vehicles plying on road thus less consumption of fuel.
(v) At home gas stoves should he cleaned properly and burners should not he left boring unnecessarily.
(vi) Pressure cookers should be preferred to pans. If pans are being used, they should he properly covered and their bottoms should not have deposits of burnt oil.
(vii) Small pans and burners should be used and pulses etc. should be dipped in water before cooking them.

Coal and Petroleum Class 8 HBSE Notes

1. We get various materials from various sources. These sources cam be natural or man-made. Natural resources are like air, water, soil, minerals, etc.
2. Natural resources are of two types according to their availability
(a) Inexhaustible
(b) Exhaustible.
3. Inexhaustible resources are those which are unlimited and are not supposed to come to an end by human use e.g. air is in exhaustible resource.
4. Exhaustible resourcs are those resources which are present in limited quantity and which can come to an end by human use e.g. forests, coal, petroleum, wildlife and natural gas, minerals, etc.
5. Coal, petroleum, natural gas etc. are called fossil fuels because they are formed by the decomposition of the dead bodies of plants and animals.
6. These fossil fuels are used by humans for their various energy requirements.
7. Coal was formed under the earth about 300 million years ago. The de forests of the earth got hurried under soil due to earthquakes and volcanic erruptions. The compressed under the layers of soil. Rising temperature under the earth converted these dead bodies into coal. Coal mainly consists of carbon.
8. The whole process of conversion of dead bodies of plants and animals into coal is called carbonization.
9. Heating of coal in absence oT cur to form coke is called destructive distillation. Destructive distillation is the process which produces various petroleum products like coaltar, coal-gas, etc.
10. Petroleum is refined to get various by-products like petrol, petroleum gas, paraffin wax, diesel, lubricating oil, etc.
11. All these resources of energy are present in limited quantity. It was a long process which took place to convert dead bodies of living beiqgs to get converted into petroleum products. So they will get exhausted if used indiscriminately.