Synthetic Fibres and Plastics - Exemplar Solutions 3

CBSE Class 8 Science
NCERT Exemplar Solutions
Synthetic Fibres and Plastic

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?
Ans. Nylon ropes are strong, elastic and lighter as compared to cotton and jute ropes.

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?
Ans. Acrylic blankets are cheap, light in weight, more durable and are available in variety of colours and designs and are also resistant to weathering. They can be easily washed at home. 

21. PVC (polyvinyl chloride) is a thermoplastic and is used for making toys, chappals, etc. Bakelite is a thermosetting plastic and is used for making electrical switches, handles of various utensils, etc. Can you write the major difference between these two types of plastics?
Ans. Thermoplastics can be transformed into a different shape easily on heating and can retain that new shape when cooled. On the other hand, thermosetting plastics when moulded once cannot be softened on heating. They do not melt on heating but they will crack or charred.

22. Fill in the blanks.
(i) A polymer is a chain of many small units joined together which are called ______.
(ii) The synthetic fibres are also known as ______ fibres.
(iii) The first fully synthetic fibre was ______.
(iv) A fibre similar to wool is ______.
(v) A plastic used for making crockery is ______.
Ans. (i) monomers
(ii) man-made
(iii) nylon
(iv) acrylic
(v) 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 plastics
(iv) polyester
(e) teflon
(v) artificial silk
Ans. (a)-(iii), (b)-(iv), (c)-(v), (d)-(ii), (e)-(i)

24. Unscramble the jumbled words given below, related to synthetic materials.
(a) anory (b) lopmery (c) relyteen (d) laspict (e) yespolter (f) felton
Ans. (a) rayon (b) polymer (c) terylene (d) plastic (e) polyester (f) Teflon