Here are extra questions from NCERT class 8 science chapter 3 Synthetic fibres and plastics.

1. Give some examples of natural fibres.

Cotton, wool, silk etc.

2. What are synthetic fibres?

Synthetic fibres are made by human beings.

3. Give an example of a natural polymer.

Cellulose

4. What is the other name of artificial silk?

Rayon

5. Rayon is obtained from …………………

Wood pulp

6. Why is rayon called a synthetic fibre although it is obtained from a natural source?

Rayon is obtained from the natural source wood pulp but it does not naturally occur. Actually, rayon is produced by chemically treating wood pulp. Hence, it is called a synthetic fibre.

7. Name a synthetic fibre made without any natural raw material.

Nylon

8. Name the first fully synthetic fibre.

Nylon

9. Nylon is made from ………………………..

Coal, water and air

10. Name some articles made from nylon

Socks, ropes, curtains, sleeping bags, seat belts

11. Why are nylon fibres used for making parachutes and ropes?

A nylon fibre is stronger than a steel wire; hence, it is used for making parachutes and ropes for rock climbing.

12. Give an example of polyester.

Terylene

13. What is PET?

PET is a familiar form of polyester. Its full form is polyethylene terephthalate.

14. Name some uses of acrylic.

Acrylic is a type of synthetic fibre used to make sweaters and shawls for keeping us warm. Acrylic is cheaper than natural wool and is available in a variety of colours. Hence, it is used to make winter clothes like sweaters and blankets.

15. Why shouldn’t we wear synthetic fibres while working in the kitchen?

If clothes made of synthetic fibres catch fire, they melt and stick to the body of the person wearing them. This can be disastrous and hence we should not wear synthetic fibres in kitchen or laboratory.

16. All the synthetic fibres are made from ………………………….

Petrochemicals

17. Name some advantages of synthetic fibres.

Synthetic fibres dry quickly, are cheaper, readily available and easy to maintain.

18. What is thermoplastics?

Plastic which gets deformed easily on heating and can be bent easily is known as thermoplastic. Examples are: polythene and PVC.

19. What is thermosetting plastic?

This is a type of plastic which when moulded once cannot be softened by heating. Examples: bakelite and melamine.

20. Name some uses of bakelite.

It is a poor conductor of heat and electricity and hence it is used for making electrical switches and handles of various utensils.

21. Why is melamine used for making floor tiles or kitchenware?

Melamine resists fire and can tolerate heat much better than other forms of plastic. Hence, it is used for making kitchenware and fabrics resisting fire.

22. Name some properties that make plastic a great material for storing various items.

Plastic is non-reactive. That means it does not corrode when exposed to water or air. For this reason, plastic can be used to store even chemicals. Plastic is light, strong and durable and can also be moulded into various shapes and sizes. In addition, plastic is cheaper than metals. Plastic is poor conductor of heat and electricity. Because of this reason electric wires have plastic covering and frying pans have handles made of plastic.

23. Why do uniforms of firemen have melamine coating?

Melamine is fire resistant and can tolerate heat better than other forms of plastic. Hence, uniforms of firemen have melamine coating.

24. Why is plastic harmful for the environment?

Plastic is a versatile material and has numerous applications in our day to day life. Unfortunately, plastic is not good for the environment because it is non biodegradable. Plastic waste gets accumulated and leads to soil and water pollution. Burning plastic is not an effective way to get rid of plastic pollution because plastic does not get completely burned. Also, during the process of burning it releases numerous poisonous gases into the atmosphere and cause air pollution. For these reasons, we must limit the use of plastic.