SCIENCE

Class: VIII

M. M: 90

Date: Time:3Hrs General Instructions:

1. There are 36 questions in this paper.
2. Read all questions carefully.
3. Marks are indicated against each question.
4. Q25-Q36 are based on practical based questions.
5. All questions are compulsory.

1 Name the cell organelle which is called as power house of the cell. 1

2 Mention the type of force acting in following cases: 1

1. Force which stops a moving ball.
2. Squeezing a piece of lemon between your fingers.

3 Why are frog's eggs covered with a layer of jelly? 4 Give the scientific term for following: 2

1. Female gametes in human beings.
2. Part of female reproductive system where fertilization takes place.
3. Artificial technique of fertilization outside the body.
4. Cell produced after fusion of gametes.

5 A bucket full of water is held above the ground. 2

1. Name the forces acting on it.
2. Why do the forces acting on it not bring a change in its state of motion?

6 Why is it difficult to move a box from the rest than when it is already in motion? 2

7 i) Differentiate between prokaryotic and eukaryotic cells on the basis of the 3

following:

1. Nuclear membrane
2. Membrane bound organelles
3. Give one example each of prokaryotic and eukaryotic organisms.

8 With reference to Polymers, answer the following: 3

1. Define the process by which polymers are formed..
2. Differentiate between synthetic and natural fibres on the basis of:
3. Cost ii) maintenance

9 i) Suggest two methods by which friction can be reduced 3

1. Explain giving example that friction is a necessary evil.

10 Give reasons for the following: 3

1. Kabaddi players rub their hands with mud before playing
2. It's difficult to walk on wet floor.
3. Brake pads are fitted in brake systems of bicycles.

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11 Name the following: 3

1. Variety of coal with lowest percentage of carbon.
2. Slow process of formation of coal.
3. Fuel used in jet aircrafts.
4. Constituent of petroleum used in making ointments and vaseline.
5. Domestic fuel which can be transported through pipes.
6. A petroleum product used in surfacing of roads.

12 What do you mean by destructive distillation of coal? Write its two products. Mention 3

one use of each of these products? 13 Sex hormones bring about changes at puberty. With reference to this, answer the 3

following:

1. Site of secretion of sex hormone in females.
2. Name of female sex hormone.
3. How these sex hormones reach their target sites?
4. Write any one change in females which occur at puberty.

14 a) "Excessive use of fossil fuels leads to global warming." Justify your answer 3

giving suitable reason.

1. Write any two ways by which fossil fuels can be conserved.

15 An object oscillates 260 times in 10 seconds. Find out the time period and frequency of 3

the object. Will the sound produced be audible to human ear or not? 16 i) Define smog. 3

1. Explain two harmful effects of air pollution (other than smog).

17 "Acid rain corrodes the marble of monuments." 3

1. What is this phenomenon called as?
2. How is acid rain caused?
3. Write another effect of acid rain.

18 Ravi read in newspaper that 25% of world's population is without potable water. He 3

discussed the matter with his science teacher and classmates. With reference to this incident answer the following:

1. Why do we need to purify water before drinking?
2. Name two diseases which can be caused by drinking contaminated water.
3. List any one method of water purification.
4. What value is depicted by Ravi's behaviour?

19 a) Label the following diagram of nucleus: 5

1. What is the function of part 'D'?
2. Differentiate between plant cell and animal cell on the basis of: i) Plastids
3. Location of nucleus

20 a) A brick is 40 cm long, 10 cm wide and 5cm thick. It weighs 20 N and is lying on 5

the ground. Find the minimum pressure exerted by the brick on the ground.

1. Explain why heavy trucks are fitted with six to eight wheels?

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