FREE CLASSES: July 2020

Monday, July 20, 2020

Algebraic Expressions and Identities

Algebraic expressions are expressions formed from the variables and the constants. A variable can take any value. The value of an expression changes with the value chosen for variables it contains.

A number line has infinite number of points. A variable can take position on number line.

Expressions containing one, two or three terms are called monomial, binomial and trinomial respectively.

Any expression having one or more terms is called polynomial.

A monomial is obtained on multiplying any monomial with another monomial.

The numerical factor of a term is called its coefficient.

An identity is a standard equality which is true for all the values of the variables in the equality.

Few commonly used identities are

I. (a + b)² = a² + b² + 2ab

II. (a – b)² = a² + b² – 2ab

III. (a + b)(a – b) =a² – b²

IV. (x + a)(x + b) = x² + (a+b)x + ab

Note – Mainly the above formulas are used to solve all the problems of this chapter.

1. Find the value of: x² – 1/5 at x= -1.

2. What is the value of x² + y² – 10 at x = 0 and y = 0?

3. Find the product of 9a, 4ab and -2a.

4. Simplify (a + b + c)(a + b - c).

5. Using identities evaluate: 8.56 * 11.60.

6. Using identities evaluate: (99)².

7. Simplify x(2x – 1) + 5 and find its value at x = -2.

8. Evaluate the value of (95)² using identities.

1. Which of the following is the numerical coefficient of x²y²?

I. 0

II. 1

III. x²

IV. y²

2. Which of the following is the numerical coefficient of -5xy?

I. 5

II. -x

III. -5

IV. -y

3. pqr is what type of polynomial?

I. Monomial

II. Binomial

III. Trimonial

IV. None of these

4. The value of x² - 5 at x= -1 is-

I. -2

II. -1

III. -4

IV. -5

5. a²-b² is a product of

I. (a+b)(a-b)

II. (a+b)(a+b)

III. (a-b)(a-b)

IV. None of these

6. Which of the following is the value of (x+ 1/x)²?

I. x²+ 1/x²

II. x²- 1/x²

III. x²+ 1/x² + 2

IV. x²+ 1/x² + 2x

7. Which of the following is obtained by subtracting x²-y² from y²- x²?

I. -2(x²-y²)

II. -2(x²+ y²)

III. 2(x²+ y²)

IV. 2(x²- y²)

8. What degree does x³ - x²y² - 8y²+ 2 have?

I. 2

II. 3

III. 4

IV. 7

9. What is the value of 5x²⁵ - 3x³² + 2x^-12 at x=1?

I. 0

II. 2

III. 4

IV. None of these

10. What is the product of (x+a) and (x+b)?

I. x²+ (a-b)x + ab

II. x² + (a+b)x - ab

III. x² + (a+b)x - ab

IV. x² + (a+b)x + ab

ANSWERS

1. II

2. III

3. I

4. III

5. I

6. III

7. I

8. III

9. III

10. I

Maximum time- 30 minutes

Maximum marks- 20

1. Add: a + b + ab; b – c + bc and c + a + ac. (2)

2. Verify the identity (x + a)(x + b) = x² + (a + b)x + ab for a = 2, b = 3 and x = 4. (3)

3. Find the volume of cuboid whose dimensions are (x² – 2); (2x + 4) and (x - 3). (4)

4. Write the terms and coefficients of 3 – xy + yz – xz. (2)

5. Simplify: (a + b +c)(a + b – c). (2)

6. Simplify the expression x(2x-1) + 5 and its value at x = -2. (3)

7. Using suitable identities find (xy + 3p)². (2)

8. Subtract 5x² – 6y² + 8y – 5 from 7x² – 5xy + 10y² + 5x – 4y. (2)

SOUND

SOUND
HOTS

1. Do all bodies produce sound?

2. Touch the bell when it stops producing sound. Can you feel the vibration? What do you understand by this?

3. Name the sound producing organ.

4. Can sound travel through vacuum?

5. What is oscillatory motion?

6. Why the sound of the baby is feeble?

7. What is ektara? Identify its vibration part.

8. Explain that sound travels in liquids as well.

9. Name some musical parts and their vibrating parts

10. How does shrillness or pitch is affected by frequency?

1. Eardrum is a part of

a. Sound producing organ

b. Skeletal system

c. Hearing organ

d. Reproductive organ

2. The hearing range of human ear is

a. 20 Hz to 20,000 Hz

b. Less than20 Hz

c. More than 20,000 Hz

d. 20 Hz to 25,000 Hz

3. The voice box is called:

a. Stomach

b. Heart

c. Larynx

d. Mouth

4. Large amplitude of sound vibrations will produce:

a. Loud sound

b. Meak sound

c. Slow sound

d. Shreak

5. The pitch of sound depends on

a. frequency

b. amplitude

c. both of these

d. none of these

6. Sound is kind of

a. Work

b. Energy

c. Force

d. None

7. To an fro motion of an object is called

a. Waves

b. Amplitude

c. Vibration

d. All of the above

8. Voice box or larynx of human process

a. Sound

b. Wind

c. Loudness

d. None

9. Sound propagates maximum in

a. Gas

b. Liquid

c. Solid

d. All

10. Noise pollution is harmful for

a. Human

b. Cat

c. Bird

d. All

ANSWERS

1. C

2. A

3. C

4. A

5. A

6. B

7. C

8. A

9. c

10. D

1. What do you meant by vibrations?

2. What is the other name for larynx?

3. Do all animals produce sound by vocal chords?

4. Write the unit of frequency.

5. What do you mean by noise pollution?

6. What is the loudness of a normal conversation?

7. Explain importance of sound in our daily life.

8. Name the organ in human that produces sound. How does it work?

9. Prove that sound travels in solids too.

10. How does loudness of sound is affected by amplitude?

QUESTIONS FROM TEXTBOOK

Q.1. Choose t.e correct answer. Sound can travel through:

(a) gases only

(b) solids only

(d) solids, liquids and gases.

Ans. (d) solids, liquids and gases.

Q.2. Voice of which of following is likely to have minimum frequency?

(a) Baby girl

(b) By boy

(d) A woman..

Ans. (a) Baby girl.

Q.3. In the following statements, tick 'T� again t hose which arse tare, ara ‘F’ against the which are false:

(a) Sound cannot trarl in vacuum.

(b) The number of oscillations per second of a vibrating objet is called its time period.

(d) For human ears, the audible range is 20 Hz to 20,000 .

(e) The lower the frequency of vibration, the higher is the pitch.

(f) Unwanted or unpleasant sound termed as music.

(g) Noise pollution may cause partial hearing impairrraent.

Ans. (a) True (b) False (c) False

(e) False (f) False (g) True.

Q.4. Fill in the blanks ith suitable words:

(a) Time taken by an object to a complete one oscillation is called__________.

(b) Loudness as determined the ___________of uibration.

(d) Unwanted sound is called __________.

(e) Shrillness of a sound is determined by the __________ of vibration.

Ans. (a) time period (b) amplitude (c) hertz (d) noise

(e) frequency

Q.5. A pendulum oscillates 40 times is 4 seconds. Find its time period and frequency.

Ans. Number of oscillations = 40

Total time = 4 seconds

Q.6. The sound from a mosquito i produced when it vibrates its wings at an average rate of 500 vibrations per seconds, what is the time period of the vibrations?

Ans. Total vibrations = 500

Time taken = 1 second

So time period = 0.002 seconds.

Q.7. Identify the part which vibrates to produce sound in following instruments.

(a) Dholak

(b) Sitar

Ans. (a) Stretched membrane

(b) Strings

Q.8. What is the difference between noise and music? Can music become noise sometimes?

Ans. The sound which is unpleasant for our ears is called noise while music is the sound which is pleasant for our ears. Music becomes noise sometimes when it crosses the bearable range of sound for our ears.

Q.9. List sources of noise pollution in your surroundings.

Ans. Sources of noise pollution: Honking of horns, loud speakers, loud sounds of machines in factories, loud sounds of T.V., radio, domestic appliances etc.

Q.10. Explain in what way noise pollution is harmful to humans?

Ans. Harmful effects of noise pollution:

(i) It causes deafness.

(ii) It causes mental illness.

(iii) It causes headache and high blood pressure.

Q.11. Your parents are going to buy a house. They awe been offered one on the road side and another three ides away from the road side. Which house would you suggest your parents to buy? Explain your answer.

Ans. I would suggest my parents to buy house three lanes away from the roadside. This house would safeguard our health and peace of mind.

Q.12. Sketch larynx and explain its function in your own words.

Ans. Larynx is also known as voice box. It has vocal cords which have air column vibrating in them, which cause sound in humans

Q.13. Lightening an thunder take place in the sky at the same time and at the same distance from us. Lightning is seen earlier and thunder is heard later. Can you explain?

Ans. The speed of light is more than that of sound. Due to more speed the light reaches us before the sound does. So lightening is seen earlier and thunder is heard later.

SAMPLE PAPER QUESTIONS

1. What do you meant by vibrations?

2. What is the other name for larynx?

3. Do all animals produce sound by vocal chords?

4. Write the unit of frequency.

5. What do you mean by noise pollution?

6. What is the loudness of a normal conversation?

7. Explain importance of sound in our daily life.

8. Name the organ in human that produces sound. How does it work?

9. Prove that sound travels in solids too.

10. How does loudness of sound is affected by amplitude?

TEST

Maximum time: 35 minutes

Maximum marks: 20 marks

1. What are the causes of noise pollution? (1)

2. Define musical sound? (1)

3. Which part of ear vibrates to produce sound? (1)

4. Define ultra and infrasonic sounds. (2)

5. What is the relation between loudness and amplitude of sound? (2)

6. Write some applications of ultrasound in daily life. (4)

7. How is the sound propagated? (2)

8. Write any four sources of noise (4)

9. What is the outer part of ear called? (1)

10. Explain with the help of activity that vibrating bodies produce sound. (2)

Metals and Non-Metals

Class VIII Science
HOTS for Metals and Non-Metals

1. Explain displacement reaction with the help of an activity.

2. Explain the reaction of non-metals with oxygen with the help of an acitivity.

3. Write the uses of metals and non-metals.

4. Write the difference between metals and non-metals on the basis of their physical properties.

5. Name two most ductile metals.

6. Sodium is stored in kerosene. Why?

7. What are oxides? Write the nature of metallic and non-metallic oxides.

8. Explain displacement reaction with the help of an example.

9. Explain the reactions of metals and non-metals with (i) Acids (ii) Air (iii) Water.

10. Write the uses of metals and non-metals in our daily life.

Choose the correct option:

1. The most reactive metal is:

(a) Iron

(b) Gold

(d) Potassium.

2. The liquid metal at room temperature

(a) Mercury

(b) Bromine

(d) Gold.

3. Non-metals are:

(a) generally liquids

(b) generally gases

(d) generally gases and liquids.

4. The metal which is stored in kerosene:

(a) Phosphorus

(b) Magnesium

5. The non-metal which is liquid at room temperature is:

(a) Carbon

(b) Iodine

(d) Chlorine.

6. Materials around us can be classified into

(a) Elements and compounds

(b) Metals and non-metals

(d) None of these.

7. All metals are solids except

(a) Sodium

(b) Calcium

(d) Hydrogen.

8. Metal oxides are of nature

(a) Acidic

(b) Basic

(d) All of these.

9. The metal which can be cut with a knife

(a) Sodium and potassium

(b) Barium and calcium

(d) Potassium and calcium.

10. When non-metals react with water then

(a) Hydrogen gas is formed

(b) Carbon dioxide gas is formed

(d) None of these.

Answers

. What do you mean by displacement reaction?

2. Give one example of displacement reaction.

3. Have you ever seen a blacksmith beating an iron piece? Do you find a change in the shape of these pieces on beating? Would you expect a similar change in wood log on beating?

4. What is malleability? Name two most malleable metals.

5. Explain that metals are good conductors of electricity with the help of an activity.

6. List some physical properties of the metals.

7. Write some physical properties of non-metals.

8. What happens when a magnesium ribbon is heated in presence of air?

9. What happens when a copper vessel is exposed in moist air?

10. Explain the reaction of sodium and water, with the help of an activity.

CONSERVATION OF PLANTS AND ANIMALS

CONSERVATION OF PLANTS AND ANIMALS

HOTS

1. What is the major threat to survival of organism?

2. Name the part of earth which supports the biodiversity.

3. Give examples of two endemic flora

4. Name the plant found in Satpura forest.

5. What is Red Data Book?

6. How do we protect wildlife?

7. What do you mean by migration? Write causes of migration.

8. What do you meant by Forest Conversation Act?

9. Name two threatened wild animals.

10. What is the tiger Project? When it was launched?

. A place in environment where an organism lives is ________

a. Home

b. Resort

c. Habitat

d. Reservoir

2. Cutting of trees on large scale is called

a. Deforestation

b. Reforestation

c. Afforestation

d. None of these

3. Deforestation takes place by

a. Human activities

b. Only by natural resources

c. Both of these

d. None of these

4. The species which are at the verge of the extinction

a. Endemic

b. Extinct

c. Endangered

d. None of these

5. The growing more and more of plants is called

a. Deforestation

b. Afforestation

c. Reforestation

d. None of these

6. Fauna indicates for

a. Plants

b. Animals

c. Bith plants and animals

d. None of these

7. The places where animals receive protection is called

a. Zoo

b. National aparks

c. Rock shelters

d. None of these

8. Project Tiger was launched on

a. 1 april 1973

b. 23 may 1973

c. 21 September 1973

d. 25 December 1973

9. Sanctuary is a place where

a. Animals are protected

b. Plants are protected

c. Office of forest department

d. None of these

10. Part of earth which supports the biodiversity is called

a. Biosphere

b. Sanctuary

c. Ecosystem reserve

d. Biotic community

ANSWERS

1. C

2. A

3. C

4. C

5. B

6. B

7. A

8. A

9. A

10. A

QUESTIONS FROM TEXTBOOK

Q.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

Ans. (a) Wildlife sanctuary (b) Endemic species

Q.2. Differentiate between the following:

(a) Wildlife sanctuary and biosphere reserve

(b) Zoo and wildlife sanctuary

(d) Flora and fauna.

Ans. (a) Wildlife sanctuary is the place where wild animals are protected in their natural habitat. Here poaching or capturing the animals is prohibited.

Biosphere reserves are the area used to conserve biodiversity like plants, animals and microorganisms. It contains many wildlife sanctuaries and national parks.

(b) Zoos are the places where some animals are protected in artificial habitats for public view.

Wildlife sanctuaries are used to protect and conserve wildlife in their natural habitats.

(c) The species which are at the verge of extinction and required protection and conservation are called endangered species.

The species which exist no more on the earth are called extinct species.

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

Q.3. Discuss the effects of deforestation on the following:

(a) Wild animals

(b) Environment

(d) Cities (Urban areas)

(e) Earth

(f) The next generation.

Ans. (a) Wild animals: Deforestation destroys the habitats of many wild animals. They are left to die without their natural shelter.

(b) Environment: Deforestation affect the environment adversely due to disturbance of ecological balance. The amount of carbon dioxide is increased in the atmosphere and causes global warming.

(c) Villages (Rural areas): The villagers depend on forests. They are closely related to forests. Due to deforestation various wild animals run to nearby villages and cause danger to them. Villagers will not get fruits, fuel, wood due to deforestation.

(d) Cities (Urban areas): Deforestation does not affect the life of cities directly badly but changes in climate affect cities.

Calamities like flood and droughts do not spare cities.

(e) Earth: Deforestation affects the earth. The fertile land of earth is converted into deserts and its temperature rises. It changes its climate and environment.

(f) The next generation: Many beautiful fauna and flora are destroyed due to deforestation. So, next generation will not be able to see them. They will not get clean and cool environment. They will not have clean and healthy environment.

Q.4. What will happen if:

(a) we go on cutting trees.

(b) the habitat of animal is disturbed.

Ans. (a) If we go on cutting trees then:

(i) Ecological balance is disturbed.

(ii) Earth will loose top fertile layer and will be converted into desert.

(iii) Floods and droughts will become more frequent.

(iv) Many animals lost their shelters.

(v) There will be a scarcity of things like fruits, paper which we get from forests.

(b) Animals become unprotected and unconserved when the habitat of animal is disturbed. It becomes endangered.

Q.5. Answer in brief:

(a) Why should we conserve biodiversity?

(b) Protected forests are also not completely safe for wild animals. Why?

(d) What are the causes and consequences of deforestation?

(e) What is Red Data Book?

(f) What do you understand by the term migration?

Ans. (a) Biodiversity is conserved, to save them from extinction.

(b) The protected forests are not also safe completely for wildlife because the poaching takes place at large scale in these areas. The poachers kill wild animals in those protected areas.

(d) Deforestation is caused due to urbanisation and industrialisation.

Deforestation is responsible for desertification and natural calamities. Many species of plants and animals are destroyed due to deforestation.

(e) Red Data Book is the record book and source book of all the endangered animals and plants.

(f) Periodical movement of a species of birds from their native place to other places due to changes in climate is called migration. The purpose of migration is for breeding and to enjoy long summer days.

Q.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 pursposes? Discuss and prepare a brief report.

Ans. The continuously cutting of trees is not justified for any project. We not only cut the trees, we snatch away the shelters of many animals, birds and other organisms. The ecological balance is also disturbed. It also causes many natural calamities.

Q.7. How can you contribute to the maintenance of green wealth of your locality? Make a list of actions to be taken by you.

Ans. (i) We can grow more and more plants in our locality.

(ii) We can protect them and provide water to them.

(iii) All the residents should be taught about the benefits of trees.

(iv) They should also be taught about the harms of cutting trees.

Q.8. Explain how deforestation leads to reduce rainfall.

Ans. Plants are the main agent to maintain the water cycle in the environment. So cutting of trees reduces the rainfall of that area. If plants will not absorb water from soil they will not evaporate in the environment to form clouds. If clouds will not be formed then no rain-fall takes place. In this way deforestation reduces rainfall.

Q.9. Why should paper be saved? Prepare a list of ways by which you can save paper.

Ans. The wood pulps and the bark of trees are used in the manufacturing of paper. If paper is not saved it causes cutting more and more trees. So we should save paper to protect our trees.

Ways to Save Paper.

(i) Paper should be recycled.

(ii) We should not throw paper here and there.

(iii) Waste paper should be collected and sent for recycling.

Q.10. 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 of plants, animals and microorganisms found in an area.

Ans.

CONSERVATION OF PLANTS AND ANIMALS

Test

Maximum time- 35 minutes

Maximum marks-20

1. What is Forest Act 1980? (1)

2. What are rock shelters? (1)

3. Write names of any two migratory birds? (1)

4. What do you mean by term deforestation? (1)

5. How does recycling and savings papers related to deforestation? (2)

6. Explain the natural and man-made causes of deforestation. (4)

7. What are the consequences of deforestation? Explain (5)

8. What are the endangered extinct animals? (2)

9. Name any two national parks. (2)

10. Explain the term ecosystem. (1)

STARS AND THE SOLAR SYSTEM

HIGH ORDER THINKING QUESTIONS

1. What are the objects like stars and the planets seen in the sky called?

2. Which day is known as �new moon day�?

3. What is a light year?

4. What is the full form of IAU.

5. Why does sun appear to rise in east and set in the west?

6. From where the polar star is not visible.

7. Name the inner planets

8. Write the name of planet in which asteroids can be seen.

9. What is responsible for change in season on earth?

10. How many planets are there in solar system?

1. Which is the brightest planet in the universe?

a. Mercury

b. Venus

c. Earth

d. Saturn

2. Which is the nearest planet to the sun?

a. Neptune

b. Mars

c. Mercury

d. Earth

3. On which planet the life exists?

a. Earth

b. Moon

c. Jupiter

d. None

4. Which planet appears to be yellowish?

a. Asteroids

b. Mars

c. Uranus

d. Saturn

5. Which is the farthest planet of solar system?

a. Neptune

b. Jupiter

c. Mercury

d. Earth

6. The first outside orbit of the earth planet is

a. Jupiter

b. Mars

c. Saturn

d. Uranus

7. Which is the largest planet in solar system?

a. Mercury

b. Mars

c. Jupiter

d. Saturn

8. What is the gap between the orbit of mars and Jupiter called?

a. Asteroids

b. Comets

c. Meteor

d. Meteorite

9. Stars appear to move from

a. West to east

b. East to west

c. North to south

d. South to west

10. The tilting of the earth is responsible for

a. Change of days

b. Change of the sun�s rays

c. Change of the season

d. None

Answers

1. B

2. C

3. A

4. D

5. A

6. B

7. C

8. A

9. B

10. C

STARS AND THE SOLAR SYSTEM
SAMPLE PAPER QUESTIONS

1. Name the star which is nearest to earth.

2. Write the names of two constellations

3. What is the speed of the light?

4. How many bright stars are there in Orion?

5. Which star is called morning or evening star?

6. Name the planets which have no moon.

7. Define phases of moon.

8. Why size of the moon decreases every day after the full moon day?

9. Why do we classify the sun as a star?

10. What is meteor?

11. Why does stars twinkle but planets do not.

12. Differentiate between stars and planets.

13. Why do phases of moon occur?

14. What is the sun? Name next nearest star. Write the distance of sun from the earth? Write the unit of the large distances.

15. Explain solar system.

Reproduction in Animals

HIGH ORDER THINKING SKILLS
Reproduction in Animals

1. Define reproduction. What are the two modes of reproduction?

2. What are the female reproductive organs?

3. What do mean by test tube baby?

4. Explain the structures of sperm and ovum.

5. Explain various modes of asexual reproduction.

6. Explain the life cycle of a frog

7. How asexual reproduction in hydra is carried out? Explain with diagram.

8. Explain the life cycle of a silk worm.

9. Explain metamorphosis.

10. What is the function of tail?

11. Which organ produces egg in female human body?

12. Give two examples of oviparous animals.

1. The animals that produce new young ones are known as

I. Oviparous

II. Viviparous

III. Both

IV. None of these

2. Tadpole is the developing stage of which of these

I. Dogs

II. Cats

III. Frogs

IV. Humans

3. Where does the fusion of male and female gametes generally take place?

I. Fallopian tube

II. Ovary

III. Uterus

IV. Zygote

4. The cell formed after fertisation is called

I. Foetus

II. Zygote

III. Embryo

IV. None of these

5. Egg are formed in the

I. Testes

II. Penis

III. Ovary

IV. None of these

6. How many modes of reproduction are there in animals?

I. One type

II. Two types

III. Three types

IV. Four types

7. A sperm consists of

I. One part

II. Two parts

III. Three parts

IV. Four parts

8. Foetus is the

I. Well developed embryo

II. Developing embryo

III. A zygote

IV. Male gamete

9. Viviparous organisms are the ones which

I. Produce eggs

II. Produce young ones

III. Both I and II

IV. None of these

10. Cloning is a mode of

I. Sexual production

II. Asexual production

III. Both I and II

IV. None of these

ANSWERS

1. II

2. III

3. I

4. II

5. III

6. II

7. III

8. I

9. II

10. II

1. Reproduction is a very important process for living organisms. It facilitates the continuation of a species.

2. Sexual reproduction takes place in human beings. Male partner releases sperm inside female�s body. Sperms and ovum fuse together in fallopian tube to form zygote. During this process the nucleus of sperm fuses with the nucleus of ovum to form a single nucleus. This entire process is called fertilization.

3. (a) in female body

(b) metamorphosis

4. (a) false

(b) true

(d) false

(e) true

(f) false

(g) false

(h) true

(i) true

(j) false

Zygote	Foetus
It contains single cell. It is formed by the fusion of ovum and sperm.	It contains many cells. It is formed by repeated divisions of zygote.

6. Asexual reproduction is a mode of reproduction were only single parent is involved. It takes place in different forms: (i) Buddings- This process takes place in hydra and bacteria. A part of these organisms starts growing further and bulging out and gradually separates from the organisms when fully developed.

(ii) This type of reproduction take place in amoeba. The nucleus of amoeba gets divided into two followed by division of their bodies. Each part gets a separate nucleus and develops into a separate amoeba. This type of reproduction is common in unicellular organisms.

7. Uterus

8. The transformation of larva into an adult through drastic changes is called metamorphosis.

Internal fertilisation	External fertilisation
(i) Takes place inside the body of female (ii) Sperms are released by the male inside female�s body	(i) Takes place outside the body of female (ii) Sperms are released in open

1. What is metamorphosis?

2. What is fertilisation? Give examples

3. Draw a well labeled diagram of a female reproductive system

4. Explain the life cycle of a frog with diagram.

5. Explain the two modes of reproduction

6. What is ovum?

7. What is a male gamete?

8. Where does fertilization take place in human body.

9. Draw the structure of a sperm

10. What are the various methods of asexual reproduction?

Reaching the Age of Adolescence

Reaching the Age of Adolescence
HOTS

1. When do noticeable changes begin in human in adolescence?

2. Do both girls and boys grow on same rate?

3. Name female hormone.

4. What is menopause?

5. What are chromosomes?

6. What is the name of hormone produced by pancreas?

7. Which endocrine gland produces the growth hormone?

8. What do you mean by metamorphosis?

9. What is the most important change marked by puberty?

10. Explain the development of sex organs in men and female.

11. What happens when egg gets fertilized?

12. Name the virus that causes AIDS. What are the medium through which this virus is transmitted?

13. Explain the sex determination of a baby in human.

14. What do you understand by Adam�s apple?

POLLUTION OF AIR AND WATER
MULTIPLE CHOICE QUESTIONS

1. Highest percentage of air consists of

a. Oxygen

b. Carbon dioxide

c. Nitrogen

d. Argon

2. The Taj Mahal is being affected by

a. Noise pollution

b. Air pollution

c. Water pollution

d. None of these

3. Most polluted river in the world is

a. Yamuna

b. Cavery

c. Chenab

d. Ganga

4. Air pollution causes

a. Global warming

b. Respiratory problems

c. Soil erosion

d. None of these

5. Green House gas is

a. Nitrogen

b. Oxygen

c. Methane

d. Carbon dioxide

6. The percentage of nitrogen is

a. 21%

b. 78%

c. 12%

d. 87%

7. What causes pollution

a. Human activities

b. Trees

c. Both of these

d. None of these

8. CNG is a

a. Polluted fuel

b. Clean fuel

c. Harmful fuel

d. None

9. Pollution of water is responsible for

a. Oil refineries

b. Paper factories

c. Sugar mills

d. All

10. Chlorofluorocarbon is used in

a. Refrigerators

b. Air conditioners

c. Perfumes

d. All

ANSWERS

1. C

2. B

3. D

4. B

5. D

6. B

7. A

8. B

9. D

QUESTIONS FROM TEXTBOOK

Q.1. What are the different ways in which water gets contaminated? Water gets contaminated by the following ways:

(i) Many industries discharge harmful chemicals to rivers and streams.

(ii) Water gets contaminated when sewage is disposed off in rivers.

(iii) Pesticides, weedecides and other chemicals also dissolve in water and get contaminated.

(iv) Breeding of microorganisms makes water polluted.

Q.2. At an individual level, how can you help reduce air pollution?

Ans. By this process we reduce air pollution:

(i) We can plant trees to reduce the level of carbon dioxide and air pollution.

(ii) By using CNG and unleaded petrol in our vehicle.

(iii) By using public transport as far as possible.

(iv) By giving general awareness about air pollution to our family and friends.

Q.3. Clear, transparent water is always fit for drinking. Comment.

Ans. Clear, transparent water is always fit for drinking. This is not true, because many microorganisms ace present in it. So we clean it by boiling.

Q.4. You are a member of the municipal body of your town. Make a list of measures that would help your town to ensure the supply of clean water to all its residents.

Ans. A list of measures that would help our town to ensure the supply of clean water to all its residents

(i) Proper cleaning of water tank.

(ii) Chlorine tablets should be made available.

(iii) To get clean water in every household, it is necessary that water reaching the houses should be treated.

Q.5. Explain the differences between pure air and polluted air.

Ans. Pure air is free from germs and harmful gases. It contains 78% nitrogen, 21% oxygen and small amount of other gases and dust particles.

Polluted air contains harmful gases and unwanted substances.

Q.6. Explain circumstances leading to acid rain. How does acid rain affect us?

Ans. Some pollutants like sulphur dioxide and nitrogen dioxide react with the water vapour present in the atmosphere to form sulphuric acid and nitric acid. The acid drops down with rain, making the rain acidic. This is called acid rain. Acid rain affects us in many ways.

(i) Acid rain corrodes the marble of the monument.

(ii) Acid rain damages building and sculptural materials.

(iii) Acid rain damages fresh water also.

(iv) Acid rain also damages our crops and also makes it poisonous.

(v) Acid rain damages the leaves of plants.

Q.7. Which of the following is not a greenhouse gas?

(a) Carbon dioxide

(b) Sulphur dioxide

(d) Nitrogen.

Ans. Nitrogen.

Q.8. Describe the `Greenhouse Effect' in your words:

Ans. Greenhouse Effect means warming the Environment. When the sun rays reach on earth, a part of the radiation that falls on the earth is absorbed by it and a part is reflected back into space. A part of the reflected radiation is trapped by the atmosphere. This trapped radiation further warms the earth. This is called Carbon House effect. CO2 is one of the gases responsible for this effect.

Q.9. Prepare a brief speech on global warming. You have to deliver the speech in your class.

Ans. Continuous increase in temperature of the earth is called global warming. There are many reasons for it. One of them is increase in population. Increase in the number of vehicles is also one of the causes. Pollution of air has also increased the global warming. Cutting trees, grazing the plants by animals increase the global warming.

Q.10. Describe the threat to the beauty of the Taj Mahal.

Ans. Over the past 2 decades, India's most famous tourist attraction Taj Mahal located at Agra, has become a matter of concern. Experts have warned that air pollution is discolouring its white marble.

So it is not only living organisms that get affected by polluted air but are also the non-living things like buildings, monuments and statues.

The industries located in and around Agra like rubber processing, automobiles, chemicals and especially, the Mathura Oil Refinery have been responsible for producing pollutants like sulphur dioxide and nitrogen dioxide. These gases react with the water vapour present in the atmosphere to form sulphuric acid and nitric acid. These come down with the rain, making the rain acidic. This is called acid rain. Acid rain has resulted in corrosion of the marble of the monument. The phenomenon is also called �Marble cancer�. Suspended particulate matter, such as the soot particles emitted by the Mathura Oil Refinery, have contributed to the yellowing of the marble.

The Supreme Court has taken steps to save the Taj. It has ordered the industries to switch to cleaner fuels like CNG ( Compressed Natural Gas) and LPG (Liquefied Petroleum Gas). Moreover, the automobiles should switch over to unleaded petrol in the Taj zone.

Q.11. Why does the increased level of nutrients in the water affect survival of aquatic organisms?

Ans. Excessive quantities of chemicals get washed away from the fields. These act as nutrients for algae to flourish. Once these algae die, they serve as food for decomposers like bacteria. A lot of oxygen in water body gets used up. This results in the decrease in the oxygen level which may kill aquatic organisms.

POLLUTION OF AIR AND WATER
SAMPLE PAPER QUESTIONS

1. Which gas is responsible for greenhouse effect?

2. What is global warming?

3. Which fuel is pollution free?

4. What are alternative renewable fuels?

5. What do you mean by �Van Mahotsav�?

6. What is water pollution and its causes?

7. What is smog?

8. What are effects of global warming/

9. What is portable water? Write its properties.

10. Explain process of water treatment to make it drinkable.

FREE CLASSES

Monday, July 20, 2020

Algebraic Expressions and Identities

SOUND

Metals and Non-Metals

CONSERVATION OF PLANTS AND ANIMALS

STARS AND THE SOLAR SYSTEM

Reproduction in Animals

Reaching the Age of Adolescence

k c nag miscellaneous question

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