NCERT Exemplar Solution Class 8 Science Chapter 3
NCERT Exemplar Solution Class 8 Science Chapter 3 Synthetic Fibres and plastics all Questions Answer Solution. NCERT Exemplar Class 8 Science Chapter 3 Solution PDF.
NCERT Exemplar Solution Class 8 Science Chapter 3: Overview
NCERT Exemplar Solution Class 8 Science Chapter 3 |
|
Board |
NCERT |
Topic |
Exemplar Problem Solution |
Class |
8 |
Subject |
Science |
Chapter |
3 |
Chapter Name |
Synthetic Fibres and plastics |
NCERT Exemplar Solution Class 8 Science Chapter 3 Synthetic Fibres and plastics
Multiple Choice Questions
1) Pick the synthetic fibre out of the following ?
a) Cotton
b) Nylon
c) Jute
d) Wool
Answer:- b) Nylon
Nylon is a synthetic fibre. Cotton, jute and wool are natural fibres.
2) Which of the following is a source of rayon ?
a)Wool
b)PET
c)Wood pulp
d)Silk
Answer:- c) Wood pulp
Rayon is a also called artificial silk. Rayon is formed from natural material i.e. Wood pulp. Wood pulp chemically treated and form Rayon.
3) Polycot is obtained by mixing
a) Nylon and wool
b) Polyester and wool
c) Nylon and cotton
d) Polyester and cotton
Answer:- d) polyester and cotton
Polyester is made up of poly + ester. Polycot is made up of mixing two fibres i.e. Polyester and cotton.
4) Which is a thermosetting plastic ?
a) Melamine
b) Polythene
c) PVC
d) Nylon
Answer:- a) Melamine
Thermosetting plastic is the plastic which does not soften by heating, when once moulded. Bakelite and melamine are examples of these.
5) The material similar to silk in appearance is
a) Nylon
b) Rayon
c) Polyester
d) Terylene
Answer:- b) Rayon
Rayon is also called as artificial silk. But it is formed from chemically treated wood pulp.
6) The most suitable material for the preparation of handles of cooking utensils is
a) Polythene
b) PVC
c) Nylon
d) Bakelite
Answer:- d) Bakelite
Bakelite is a synthetic material, it is bad Conductor of heat and electricity. Therefore it is used to prepare handles of utensils.
7)Which of the following is not a common property of plastics ?
a) Non- reactive
b) Light in weight
c) Durable
d) Good conductor of electricity
Answer:- d) Good conductor of electricity
Plastic are bad Conductor of heat and electricity.
8) Which of the following represents the correct match for items in column A with those in columnB .
Column A Column B
I)Nylon i) thermoplastic
II) PVC ii) Thermosetting plastic
III) Bakelite iii) Fibre
a) I- (ii), II-(iii), III-(i)
b) I- (iii), II-(i), III-(ii)
c) I-(ii), II-(i), III- (iii)
d) I-(iii), II- (ii), III- (i)
Answer:- b) I-(iii),II- (i), III-(ii)
Nylon is polymer, PVC is thermosetting Plastics and Bakelite is thermoplastic.
These all are synthetic polymers.
9) Which of the following groups contain all synthetic substances?
a) Nylon , terylene, wool
b) Cotton, polycot, Rayon
c) PVC , polythene, Bakelite
d) Acrylic, silk , wool
Answer:- c) PVC, polythene, Bakelite
PVC, polythene and Bakelite are all synthetic material. Other groups contains some natural fibres in it.
10) The material which is commonly used for making kitchen containers is
a) PVC
b) Acrylic
c) Teflon
d) PET
Answer:-d) PET
PET is polyethylene terephthalate. These is a type of thermoplastic which can be bend easily. These is used to make containers.
Very Short Answer Questions
11) Cotton is a natural polymer. What is its chemical name?
Answer:- The natural polymer cotton has an chemical name which is Cellulose.
12) A synthetic fiber which looks like silk is obtained by chemical treatment of wood pulp. Is is, therefore, known as artificial silk. What it is common name?
Answer:-
The common name of an artificial silk is Rayon. Rayon is formed after wood pulp is treated with chemicals.
13) Terrycotis made by mixing two types of fibres. What the names of the fibres.
Answer:- terrycot made up of mixing of two types of fibres these are teryleneand cotton.
14) Plastic articles are available in all possible shapes and sizes. Can you tell why?
Answer:- Plastic is a polymer. This plastic articles are available in any shape and size. Because These are easily mouldable. Plastic can be recycled, reused, melted, or rolled.
15) Plastic is used for making a large variety of articles of daily use and these articles are very attractive. But it is advised to avoid the use of plastic as far as possible. Why?
Answer:-We should avoid the use of plastic because plastic is non-biodegradable. Non-biodegradable is the material which does not get easily decomposed by natural processes. Plastic takes many years to decomposed. It increases the Pollution . If we burnt the Plastic then the poisonous fumes releases into the atmosphere which is also hazardous. Therefore using plastic is not environmental friendly.
16) Why is it not advisable to burn plastic and synthetic fabrics?
Answer:- Plastic and synthetic fabric stakes lots of years to degrade. These are not environment friendly at all. The accumulation of these waste causes more pollution in the environment. The burning process of the Plastic and synthetic fabrics is slow And after burning also it does not get completely burnt. The burning of these materials releases poisonous fumes in the atmosphere. These causes the severe air Pollution. Therefore it is not advisable to burn plastic and synthetic fabrics.
17) Select the articles from the following list which are biodegradable.
a) Paper
b) Woolen clothes
c) Aluminum can
d) Plastic bag
e) Peels of vegetables
Answer:- the articles which are biodegradable are –
Paper
Woollen clothes
Peels of vegetables
18) A bucket made of plastic does not rust like a bucket made of iron. Why?
Answer:- Plastic is made up of polymer. Plastic is not a metal like iron. Iron reacts with the atmospheric air and thus it gets rust. These are poor conductor of heat and electricity. Plastic is non-reactive material, it cannot react with air or water and therefore it does not rust.
Short Answer Questions
19) Rohit took with him some nylon ropes, when he was going for rock climbing. Can you tell why he selected nylon ropes instead of ropes made of cotton or jute?
Answer:- Nylon is a man made synthetic fibre. It is stronger than the jute. also it is elastic and light weight. Nylon issued in the parachutes and making ropes. These ropes are used for rock climbing. Nylon rope is stronger than a steel wire. Cotton and jute ropes are not that much stronger, therefore nylon ropes are used for Mountain climbing.
20) A lady went to the market to buy a blanket. The shopkeeper showed her blankets made of acrylic fibres as well as made of wool. She preferred to buy an acrylic blanket. Can you guess why?
Answer:-
Woollen blankets or sweaters are costly as compared to the synthetic fibre acrylic. Acrylic is also looks like wool. Many of the woollen clothes or blankets in the market are made up of acrylic. Acrylic is light in weight. It is available in so much different colours. It is durable and cheap as compared to the wool. It is easy to wash. Therefore it is the Choice of many people.
21) PVC (polyvinyl chloride) is a thermoplastic and is used for making toys, chappals, etc. Bakelite is a Thermosetting plastic and it used making electrical switches, handles of various utensils, etc. Can you write the major difference between these two types of plastics?
Answer:- Thermosetting Plastics are the plastics which if moulded once , does not get softened by heating after that. Examples of these type of plastics are backlight and melamine. On the other hand, Thermoplastics are plastics which are easily mouldable. These are easily deformed when heated and can be easily bent. Examples of these type of plastic are polythene and PVC. These is the major difference between the two type of plastics.
22) Fill in the blanks.
i) A polymer is a chain of many small units joined together which are called_________.
Answer:- A polymer is a chain of many small units joined together which are called monomers.
ii) The synthetic fibres are also known as ___________ fibres.
Answer:- The synthetic fibres are also known asman- made fibres.
iii) The first fully synthetic fibre was _________.
Answer:- the first fully synthetic fibre was Nylon.
iv)A fibres similar to wool is ___________.
Answer:- A fibres similar to wool is Acrylic
v) A plastic used for making crockery is ____________.
Answer:- A Plastic used for making crockery is melamine.
23) Match items in list A with the items of list B.
List A List B
a) Nylon i) non- stick coating
b) PET ii) electric switches
c) Rayon iii) parachutes
d)Thermosetting Plastic iv) polyester
e)Teflon v) artificial silk
Answer:-
A) Nylon → iii) parachutes
B) PET →iv) polyester
C) Rayon → v) Artificial silk
D) thermosetting Plastic→ ii) Electric switches
E) Teflon → i) non- stick coating
24) Unscramble the jumbled words given below , related to synthetic materials.
a) Anory
Answer:- Rayon
b) Lopmery
Answer:- Polymer
c) Relyteen
Answer:- terylene
d) Laspict
Answer:- Plastic
e) Yespolter
Answer:- polyester
f)Felton
Answer:- Teflon
Long Answer Questions
25) Indicate whether the following statements are True or false. Also write the false statements in their correct form.
I)The fabric terywool is obtained by mixing terylene and wool.
Answer:- True
II)synthetic fibres do not melt on heating.
Answer:- False.
Synthetic fibres also melt on heating as like natural fibres.
III) It is risky to wear synthetic clothes while working in the kitchen.
Answer:- True
IV) Most of the plastics are biodegradable.
Answer:- False.
Plastics are mostly non -biodegradable. Therefore they are hazardous for living being.
26) Write the importance of synthetic polymers in our life.
Answer:-
The importance of synthetic polymers are as below:-
1) Rayon :- Rayon is mixed with other fibre like cotton to make clothes andbed sheets, mixed with wool to make carpets. Etc.
2) Nylon:- nylon ropes are used for making parachutes, climbing rocks, and other household work like drying clothes, to tie something. Nylon is also used in tents, socks, toothbrushes, car seat belts, curtains and sleeping bags. Etc.
3) Terylene:- it is used in the making fabric.
4) Polyethylene terephthalate (PET) :- it is used in making utensils, films, wires, bottles, etc.
5) Acrylic:- acrylic is used to make shawls, sweaters, and blankets.
6) Plastics:-plastic is used to make so much variety of useful items such as-
Thermoplastics:-
Eg. Polythene and PVC
used in making toys, combs, containers etc.
Thermosetting Plastics :-
Eg. Backlit and melamine
It is used in making floor tiles, fabric to resist fire, kitchenware, electric switches, plastic bottles. Etc
27)Despite being very useful it is advised to restrict the use of plastic. Why it is so?
Can you suggest some methods to limit it’s consumption?
Answer:-
As we know plastic is very useful in our day to day life, but it is increasing pollution on our earth. As plastic is Non- biodegradable material. It takes several hundred years to decompose. It is not environment friendly at all.
Whenever we take something in polythene bags we throw it after use, sometimes there is remained food is there in it, which is tried to eat by cattle or dogs, they swallow food along with the polythene bags which causes severe health problems to them also may cause death.
Throwing in drain, these polythene bags causes clogging up of the drainage.
Burning of these plastic material causes lots air pollution, these release hazardous poisonous fumes into the atmosphere during burning.
Therefore we should avoid to use plastic material as far as possible.
we can find out some ways to do that work instead of using plastic.
Such as to using paper, cotton or jute bag for the shopping.
Waste should be collected and separate as biodegradable and non-biodegradable and further disposed separately. These will help in degradation of plastic or non- plastic material.
Plastic waste should be recycled, Reuse, reduce, recover and refuse.
These habits of using plastic will make it less hazardous for environment.
28) Write an activity to show that synthetic fibres are stronger than the cotton fibres.
Answer:-
We can perform an activity to show that synthetic fibres are stronger than the cotton fibres as follows-
For performing these activity we should take an iron stand with a clamp. An cotton yarn and a nylon fibre of some specific length about 50 cm.
Tie up cotton yarn to the clamp first and hang a free suspended pan to the other end of yarn, add weight over the pan, increase the Weight till the thread is break.
Perform the same procedure with the nylon thread.
We will observe that the natural fibre cotton will break in only little weight while the synthetic fibre nylon required more weight to break.
29) Complete the crossword given below with the help of clues.
Across-
(1) Substance used as synthetic wool (7)
(2) A plastic used for making containers and carry bags(9)
(3) Substances made up of large number of smaller molecules (7)
(4) Another name of this compound is artificial silk(5)
Down-
(5) A type of fibre obtained naturally from cocoon.(4)
(6) A synthetic fibre classified as polyester (8)
(7) A polymer used for making rope(5).
Answer:-