Synthetic Fibres and Plastics - Exemplar Solutions 4

CBSE Class 8 Science
NCERT Exemplar Solutions
CHAPTER 03
Synthetic Fibres and Plastic
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.
(ii) Synthetic fibres do not melt on heating.
(iii) It is risky to wear synthetic clothes while working in the kitchen.
(iv) Most of the plastics are biodegradable.
Ans. (i) True
(ii) False, synthetic fibres melt on heating
(iii) True
(iv) False, most of the plastics are non-biodegradable.
26. Write the importance of synthetic polymers in our life.
Ans. Synthetic polymers have become very important in our lives. They are used in clothing, home furnishings, industrial use etc. Synthetic polymer like rayon, nylon, polyester are used for making clothes and accessories.
Nylons for making umbrellas, leegings, raincoats, curtains etc
Polyester are used fir making sarees , shirts and polyester when combined with natural fibres makes wrinkle free fabric which is very much on demand these days.
PET (Polyethylene terepthanene) a type of polyester are used fo making bottles and containers which are durable, flexible, light weight and also relatively inexpensive.
Plastics also a type of polymer are widely used material today. They are used in making electrical and electronic components, parts of vehicles, packaging industries,toys etc
Terylene a variety of polyester are also used to make fabric by mixing with other fabrics.
27. Despite being very useful it is advised to restrict the use of plastic. Why is it so? Can you suggest some methods to limit its consumption?
Ans. Plastic is a non-biodegradable material and as such it causes land pollution. At the same time burning such materials in the form of garbage causes serious air pollution. Reducing it’s use, reusing it for some other purpose and recycling may limit its overall consumption and reduce environmental pollution.
Despite being very useful it is advised to restrict the use of plastic because plastic is a non-biodegradable material and its widespread use is causing environmental problems and health risks. Plastics cannot be decomposed by the action of fungi and bacteria. It takes years to decay a single plastic bag completely and plastic waste is increasing at an alarming rate causing land pollution. At the same time, since plastics are non-biodegradable the only way to get rid of them is by burning whichreleases toxic fumes into the environment causing serious air pollution.
To limit its consumption, the only way to manage plastic is to reduce, reuse and reccycle.
Reduce- We can limit the use of plastics by-:
                a) carrying our own cloth bag while going for shopping.
                b) not carrying water bottle, lunch boxes, pencil made of plastics.
                c) storing things in jars or containers not made of plastic.
Reuse-  We can reuse all the plastics we have at home.Some of the things we can do at home are:- a) Use empty soft drink bottles to store water.
        b) Reuse polythene bags that we get from the market.
       c) Use empty plastic containers to store things.
Recycle- Some of the plastics can be recycled.Thermoplastics can be melted and reshaped to other products. A plastic bottle used to store beverages could be reformed into the fibres of a jacket.
Plastic bottles can be recycled and used as flower pots stc.
28. Write an activity to show that synthetic fibres are stronger than the cotton fibres.
Ans. To show that synthetic fibres are stronger than the cotton fibres, following activity can be performed.
  • Take an iron stand fitted with a clamp.
  • Tie a cotton thread on the clamp so that it hangs freely and then suspend an iron block.
  • Add weight one by one till the thread breaks.
  • Repeat the same activity using a nylon thread.
  • You will observe that nylon thread will be able to withstand more weight as composed to the cotton thread due to its good elasticity and high tensile strength.
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. Substance made up of large number of smaller molecules (7)
4. Another name for 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)
Ans.