NCERT Solutions Class 8 Science Chapter 3 Synthetic Fibres And Plastics
NCERT Solutions Class 8 Science Chapter 3 Synthetic Fibres And Plastics: National Council of Educational Research and Training Class 8 Science Chapter 3 Solutions – Synthetic Fibres And Plastics. NCERT Solutions Class 8 Science Chapter 3 PDF Download.
NCERT Solutions Class 8 Science Chapter 3: Overview
|
Board |
NCERT |
| Class |
8 |
|
Subject |
Science |
| Chapter |
3 |
|
Chapter Name |
Synthetic Fibres And Plastics |
| Topic |
Exercise Solutions |
NCERT Solutions Class 8 Science Chapter 3 – Synthetic Fibres And Plastics
CHAPTER: – 3
(SYNTHETIC FIBRES AND PLASTICS )
Exercise: –
1)Explain why some fibres are called synthetic.
Ans: – The synthetic which we used in daily basis is nothing just the petrochemical products or polymers. As this petrochemical helps in making the synthetic as similarities with the fibres this are know as synthetic. This uses of synthetic also increasing daily basis.
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.
(Synthetic fibres is made from petrochemical product which is different)
3)Fill in the blanks with appropriate words.
(a) Synthetic fibres are also called ____artificial______ or ___manmade_______ fibres.
Explanation – (As these synthetic fibres are made by applying different temperature from petrochemical)
(b) Synthetic fibres are synthesised from raw material called ___petrochemical____.
Explanation – (This also the main source of synthetic fibres)
(c) Like synthetic fibres, plastic is also a _____polymer_____ .
Explanation – (This plastic is made from the polymer like pvc, polyethylene etc)
4) Give examples which indicate that nylon fibres are very strong.
Ans: – We have seen the application of the nylon fibres in parachute or rope in this nylon is the main and only reliable source. So, after this uses in climbing or paragliding, we came understand that the nylon fibres are very strong.
5) Explain why plastic containers are favoured for storing food.
Ans: – The food when came to contact with the air it became rancid or it react with the moisture present in air so we must keep it in a place where air doesn’t travel. So, when we used plastic containers which restricted the passes of air.
6)Explain the difference between thermoplastic and thermosetting plastics.
Ans: The properties of both the thermoplastic and thermosetting polymer are different as after applying heat the thermoplastic polymer became soft but the thermosetting polymer not. The thermoplastic doesn’t used in making hard substance but thermosetting is used.
7) Explain why the following are made of thermosetting plastics.
(a) Saucepan handles
(b) Electric plugs/switches/plug boards.
Ans: – As the saucepan attached the high temperature while cooking so if it doesn’t make from the thermosetting polymer then it will become melt.
In electric plugs or the switch or plug boards sometimes touches the high temperature for the flowing of high current so we need made this object with such that have temperature resist so we use thermosetting polymer.
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: – The material which will be recycled is plastic toys, carry bags, plastic bowls, plastic covering on electric wire.
The material which would not be recycled telephone instrument, cooker handles, ball point pens, electrical switch.
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: – As the cotton shirts allow the air passing through it so, after wearing we feel comfortable in the hot summer day. And by using synthetic shirts our body will uncomfortable because of heat and sweating so, cotton is preferable here.
10) Give examples to show that plastics are noncorrosive in nature.
Ans: – The reason for the noncorrosive of plastic are
It doesn’t react with chemical.
It doesn’t decompose.
There is no rust above the plastic.
11) Should the handle and bristles of a tooth brush be made of the same material? Explain your answer.
Ans: – In this case we need a material which is softer as well as hygiene in case of bristle its necessary. But in case of the handle of the tooth brush the material should be lights stronger that the previous one. So, for making this two-thing different material should be used.
12)‘Avoid plastics as far as possible’. Comment on this advice.
Ans: – As the plastic is non biodegradable element which means it doesn’t mix with the soil or water when we throw it unnecessarily and became a reason of pollution. So, day by day we should avoid the plastic uses as possible.
13) Match the terms of column A correctly with the phrases given in column B.
Ans: –
|
Column A |
Column B |
| (i)Polyester. | Fabrics do not wrinkle |
| (ii) Teflon. | used to make non stick cookers |
| (iii)Rayon. | Prepared by using wood pulp. |
| (iv) Nylon. | Used for the making parachute and Stoking. |
14) Manufacturing synthetic fibres is actually helping conservation of forests. Comment.
Ans: – The uses of the synthetic fibres actually help us in conservation of the forest as the synthetic fibres are made with the petrochemical substance which came from the decompose store in ground year after year. As a result of that the uses of the trees become less which helps in growing the forest.
15) Describe an activity to show that thermoplastic is a poor conductor of electricity.
Ans: – The thermoplastic is poor conductor of heat which we seen in our regular uses like if we place a plastic which we use for the shopping food, we will see that it melts after touching the, asthis made from the thermoplastic polymer also.
