NCERT Solutions for Class 8th Science
Chapter 3. Synthetic Fibres And Plastics
Text Book Exercise
Text Book Exercise:
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: I wiil advice rana to wear cotton clothes. Cotton clothes, which are natural fabric, do not contain heat, instead they reflect out heat. Besides, they also provide aeration. So, during summar, we prefer cotton clothes, and not the synthetic clothes.
10. Give examples to show that plastics are noncorrosive in nature.
Answer: The plastics are non-corrosive, that is, they do not react or do not have chemical reaction with the materials contained in it. That is many containers are made up of plastics.
11. Should the handle and bristles of a tooth brush be made of the same material? Explain your answer.
Answer:Yes, because both should be made of the material, which is light in weight, have good strenght and hygienic.
12. ‘Avoid plastics as far as possible’. Comment on this advice.
Answer: Since plastic takes serval years to decompose, it is not enviroment frindly. It causes enviromental pollution. Besides, the buring process in the synthetic material is quit slow and it does not burn completelely. in the process it releases lots of poisonous fames into the atmosphere causing air pollution. So, we should avoid the use of plastics as far as possible.
13. Match the terms of column A correctly with the phrases given in column 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) Fabrics do not wrinkle easily
(i) (d), (ii) (c), (iii) (a), (iv) (b).
14. ‘Manufacturing synthetic fibres is actually helping conservation of forests’.
Answer. The synthetic fibres are made up of petrochemicals.So, the manufacture of synthetic fibres does not depend upon plant and trees. These synthetic fibres cater the need of people upto great extent.Thus the forests are not destroyed to manufacture clothes and other items. So, indirectly, we can come to a conclusion that manufacturing synthetic fibres is actually helping conversation of forests.
15. Describe an activity to show that thermoplastic is a poor conductor of electricity.
Answer: If we make an experimental set up using copper wire, a thermoplastic object, a bulb and a cell, as shown in the figure given below, the bulb does not glow.
However, if the thermoplastic object is removed from the circuit, the bulb glow up. This shows that thermoplastics object are bad conductor of electricity.