Synthetic Fibres and Plastics(NCERT Solutions, Class 8)

(1) Explain why some fibre are called synthetic.

Ans- Some fibres are called synthetic because these are made by humans without use of natural resources. Some examples of synthetic fibres are rayon, nylon etc.

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(3) Fill in the blanks with appropriate words:-

(a) Synthetic fibers ate also called ____ or ___ fibres.

(b) Synthetic fibres are synthesized from raw material called ____.

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

Ans-

(a) Synthetic fibers ate also called artificial  or handmade fibres.

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

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

(4)Give examples which indicate that nyon fibres are very strong.

Ans-Examples which indicate that nylon fibres are very strong are given below:-

(a)Nylon wires are used in parachutes.

(b) Nylon wires are used in ropes of rock climbing.

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

Ans- Plastic contaires are favoured for storing food because these are

(i) very strong

(ii) durable

(iii) light in weight

(iv) do not break easily

(6)Explain the difference between thermoplastic and thermosetting plastics.

Ans-

Differences between thermoplastic and thermosetting plastics

SN Thermoplastic Thermosetting plastic
1 It can be bent easily on heating. It can not bent easily on heating.
2 It can be easily deformed on heating. It can not be deformed on heating.
3 It is good conductor of heat. It is poor conductor of heat and electricity.
4 Eg:- Polythene, PVC Eg:- Bakalite, Melamine
5 Toys, bottles , containers ,comb etc can be made by it. Pans handles, electric switches, kitchenware etc can be made by it.

(7)Explain why the following are made of thermosetting plastics.

(a) Sauce pan handles

(b) Electric plugs/switches/plug boards.

Ans-

(a) Sauce pan handles are made of thermosetting plastics because thermosetting plastics are poor conductor of the heat. Therefore, saucepan handles do not get hot easily.

(b) Electric plugs/switches/plug board are mado of thermosetting plastics because thermosetting plastic is poor conductor of electricity.Therefore, Electric plugs/switches/plug boards made by thermosetting plastics are safe for use.

(8) Categorise the materials of the following products into `can be recycled and cannot be recycled’.

Ans-

Categorization of material of given products

SN Products Can be recycled Can not be recycled
1 Telephone instrument  Picture1
2 Plastics toys  Picture1
3 Cooker handlels  Picture1
4 Carry bags  Picture1
5 Ball point pens  Picture1
6 Plastics bowls  Picture1
7 plastic covering on electrical wires  Picture1
8 Plastic chairs  Picture1
9 Electrical switches  Picture1

Note: This question is to check our understanding of properties of thermoplastic and thermosetting plastic. Out of the items mentioned above, some can be created with both thermosetting and thermoplastic material, such as toys. Extremely popular toy brand, Legos are made up of thermosetting material and hence are not recyclable, whereas various cheap toys are made using the thermoplastic material making them recyclable. Answer of this question may vary.

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

Ans- Rana should buy cotton shirts because he wants to buy shirt for summer. Cotton absorbs more water in comparison of synthetic fibre. So cotton shirt will absorb more swat an dRana will feel comfertable. While synthetic fibre will not absorb more swat. So synthetic material shirts will make him feel hot .Therefore buying a cotton shirt will be a wise decision.

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

Ans-Plastics are non corrosive in nature because

(i) Plastics are non-biodegradable.

(ii)they leave posinous fumes on burning which polluted environment.

(iii)they choked our drainage systems.

(11)Should the handles and bristles of a tooth brush be made of the same material? Explain your answer?

Ans-The brushes of the tooth brush should be made of nylon because nylon is soft synthetic fibre. Therefore, it is useful for bristles.While hndles of the tooth brush should be made of plastic because plastic can be hard which is useful for purpose of handles.

(12)`Avoid plastics as far as possible’. Comment on this advice.

Ans-`Avoid plastics as far as possible’ because

(a)It is non bio degradable.

(b)It can not be burnt completely. It fumes releases poisonous air in the environment.

(c) The street animals swallowed polythene bags while trying to eat food from garbage dumps. These bags choked their respiratory system.

(d) Plastics bags are also responsible for clogging the drains.

So we should  protect environment from the plastics by –

(a)not throwing plastics bottles or bags on road or in the water bodies.

(b) using cotton bags for shopping.

(c) trying to minimum use of plastics.

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

A                                                    B

(i) Polyester                                      (a)Prepared by using wood pulp

(ii) Teflon                                          (b) Used for making parachutes and stockings

(iii)Rayon                                          (c)Used to make non stick cookwares

(iv)Nylon                                           (d) Fabric donot wrinkle easily

Ans-

A                                                    B

(i) Polyester                                    (d) Fabric donot 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-

Synthetic fibres are made by non natural resources. In this way it is right to say that we conserve forests while making synthetic fibre. But synthetic fibres are non bio degradable.Hence, these fibres are not environmental friendly. Therefore it is not good to use synthetic fibre.

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

Ans-

Take a piece of plastic from a carry bag and a remote .

schoolhelpbygunjan.wordpress.com | Activity to show that thermoplastic is a poor conductor of electricity| NCERT | Class 8

 

Now, put plastic in remote before putting batteries.

schoolhelpbygunjan.wordpress.com | Activity to show that thermoplastic is a poor conductor of electricity| NCERT | Class 8

Now, it is an open circuit. You can not operate your air conditioner with new setting. Now remove thermoplastic from the remote.

schoolhelpbygunjan.wordpress.com | Activity to show that thermoplastic is a poor conductor of electricity| NCERT | Class 8

You can operate your air conditioner with remote.It shows that thermoplastic is a poor conductor of the electricity.

 

Helping Topics

Some Indian breeds of sheep

Wool producing animals in India

Burning smell of different fibres

Practice sheet, class 8

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