NCERT Class VIII Science Solution: Chapter 3-Synthetics Fibres and Plastics Part 5

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Question 26:

Write the importance of synthetic polymers in our life.

Answer:

Write uses of synthetic polymers like nylon, acrylic, Terylene, PET, plastics, etc.

  1. Nylon: It is used for making ropes for rock climbing, fishing nets, raincoats, parachutes and tyre cords etc.

  2. Acrylic: It is used for sweaters, track suits, lining for boots and gloves and in furnishing fabrics and carpets.

  3. Terylene: It is used in textile industry to make clothes like sarees, tapestry and dress material. It is also mixed with natural fibre like cotton and wool to make more variety of clothes.

  4. Plastics: It is used to store food item, water, milk, pickles, dry food etc. Plastic containers seem most convenient.

Question 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?

Answer:

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 its use, reusing it for some other purpose and recycling may limit its overall consumption and reduce environmental pollution.

Question 28:

Write an activity to show that synthetic fibres are stronger than the cotton fibres.

Answer:

Activity take threads of cotton and nylon of about same length and thickness. Hang cotton, thread from a stand. Attach a pan at the other end of thread.

Add weights, one by one, to the pan until the thread breaks note the total weight required to break the cotton thread. This gives a measure of the tensile strength of the thread. Repeat the same with nylon thread.

Image of arrangement to dtermine the relative trengts of natural fibres and synthetic fibres.

Relative Strengts of Natural and Synthetic Fibres

Image of arrangement to dtermine the relative trengts of natural fibres and synthetic fibres.

Conclusion:

Much more weight is required to break the nylon thread showing that nylon thread has a greater strength that the cotton thread.

Question 29:

Complete the crossword given below with the help of clues.

Result for Complete the crossword (Q)

Complete the Crossword (Q)

Result for Complete the crossword (Q)

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)

Answer:

Result for Complete the crossword (A)

Complete the Crossword (A)

Result for Complete the crossword (A)

Across:

1. Substance used as synthetic wool - Acrylic

2. A plastic used for making containers and carry bags - Polythene

3. Substance made up of large number of smaller molecules - Polymer

4. Another name for this compound is artificial silk - Rayon

Down:

5. A type of fibre obtained naturally from cocoon - Silk

6. A synthetic fibre classified as polyester - Terylene

7. A polymer used for making rope - Nylon

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