Synthetic Fibres And Plastics

Exercises 

1. Explain why some fibres are called synthetic.

Ans:-

Fabrics are made from fibres obtained from natural or artificial sources.The fibres which are made by human beings are called synthetic fibres.


2. Mark the correct answer.

Rayon is different from synthetic fibres because
(a) it has a silk-like appearance.
(b) it is obtained from wood pulp.
(c) its fibres can also be woven like those of natural fibres.

Ans:-
(b) it is obtained from wood pulp.


3. Fill in the blanks with appropriate words.

(a) Synthetic fibres are also called      artificial      or      man-made     fibres.

(b) Synthetic fibres are synthesised from raw material called      petrochemicals     .

(c) Like synthetic fibres, plastic is also a       polymer      .


4. Give examples which indicate that nylon fibres are very strong.

Ans:-
Nylon is a strong synthetic fibre. Following examples can prove this :

1. nylon is elastic, and stronger than a steel wire.
2. have high tensile strength.
3. used for making parachutes and ropes for rock climbing.
4. used in making seat-belts, fish-nets etc.

5. Explain why plastic containers are favoured for storing food.

Ans:-
Plastic containers seem most convenient for storing food. This is so because of their light weight, lower price, good strength and easy handling.


6. Explain the difference between thermoplastic and thermosetting plastics.

Ans:-

7. Explain why the following are made of thermosetting plastics.
(a) Saucepan handles
(b) Electric plugs/switches/plug boards

Ans:-
(a) Melamine a kind of thermosetting plastic, is a versatile material. It resists fire and can tolerate heat better than other plastics. That's why saucepan handles are made up of thermosetting plastics.

(b) Bakelite a kind of thermosetting plastic, is a poor conductor of heat and electricity so, its is used to make electric plugs , switches, plug boards etc.

8. Categorise the materials of the following products into ‘can be recycled’ and ‘cannot be recycled’.
Telephone instruments, plastic toys, cooker handles, carry bags, ball point pens, plastic bowls, plastic covering on electrical wires, plastic chairs, electrical switches.

Ans:-

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

Ans:-
No, he shouldn't buy shirts made of up of synthetic material because synthetic materials are more prone to heat. melt on heating. This is actually a disadvantage of synthetic fibres. If the clothes catch fire, it can be disastrous as the fabric melts and sticks to the body of the person wearing it.
With respect to summer if he wear such clothes, he'll feel more hot. So, he should buy cotton shirts as cotton is a good absorber of water and helps in evaporating the sweat and keeps the body cool.

10. Give examples to show that plastics are noncorrosive in nature.

Ans:-
Plastics are noncorrosive in nature because they are not reactive. They don't react with air and water so don't corrode.That is why they are used to store various kinds of material, including many chemicals.

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

Ans:-
No, handle and bristles of a tooth brush be made of the same material because, the handle of toothbrush needs to be strong and hard while bristles should be soft, smooth and flexible so that it doesn't hurt us.

12. ‘Avoid plastics as far as possible’. Comment on this advice.

Ans:-
'Avoid plastics as far as possible'. This quotation is absolutely right because of the following reasons :

1. Plastics are non biodegradable waste materials because microorganisms cannot break them to simpler units.
2. It not environment- friendly as it causes soil pollution when dumped.
3. While burning, releases lots of poisonous fumes and bad smell which have a bad impact on human's health as well as it creates air pollution.
4. Responsible for clogging of drains.
5. If swallowed by animals then it chokes the respiratory system or form lining in their stomachs and even can lead to their death.

13. Match the terms of column A correctly with the phrases given in column B.

Ans:-
(i) Polyester - (d) Fabrics do not wrinkle easily
(ii) Teflon - (c) Used to make non-stick cookwares
(iii) Rayon - (a) Prepared by using wood pulp
(iv) Nylon - (b) Used for making parachutes and stockings


14. ‘Manufacturing synthetic fibres is actually helping conservation of forests’. Comment.

Ans:-
Yes, the statement is correct because if we rely more on natural fibres and we'll need lots of raw materials and for that maximum forests would be cleaned. As synthetic fibres are obtained from petrochemicals, very less use of raw materials is needed, so trees, plants, forests remains conserved.

15. Describe an activity to show that thermoplastic is a poor conductor of electricity.

Ans:-

Materials required:- plastic pipe, copper wires, battery, metal pipe/rod, bulb 

Build a circuit using the above materials.

1. Using metal pipe :- Te bulb glows
2. Using plastic pipe (replace metal pipe) :- the bulb doesn't glow. 

This shows that plastic pipe which is a thermoplastic is a poor conductor of electricity.