NCERT Class VIII Science Solution: Chapter 3-Synthetics Fibres and Plastics Part 4

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Question 9:

Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from synthetic material? Advise Rana, giving your reason.

Answer:

Rana is advised to buy a cotton shirt for summers because cotton absorbs the sweat and the pores in cotton allows easy evaporation and keeps our body cool, whereas synthetic shirts don’t absorb sweat so, they are very uncomfortable to wear in summers.

Question 10:

Give examples to show that plastics are noncorrosive in nature.

Answer:

We can store various kinds of chemicals and other materials in plastic containers because they are non-reactive and does not react with water and air.

  • Teflon, a kind of plastic is used as a coating to manufacture non-stick cookware.

  • Bakelite is a poor conductor of heat and electricity so it is used for making electric switches and handles of the utensils.

  • Melamine is used for making floor tiles and kitchenware

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Question 11:

Should the handle and bristles of a tooth brush be made of the same material? Explain your answer.

Answer:

The bristles of a tooth brush should be made of soft material so that it does not harm the gums and the handle should be made of hard material so that it can give a firm grip. Therefore, the bristles are made up of nylon fibres which are strong, elastic, lustrous, light weight and easy to handle and the handle is made of hard plastic as it is strong, durable, poor conductor of heat and electricity.