NCERT 8th Class (CBSE) Science: Synthetic Fibres and Plastics

Question: Explain the discovery and unique features of nylon.

Answer: Nylon was made in 1931. The term ‘nylon’ has been derived from letters of ‘New York’ and ‘London’. No ingredient from plant or animal source was used in making nylon, as it is made from coal, water and air. Hence, nylon is called the first truly synthetic fibre.

1. Nylon is strong, light and elastic.
2. It is lustrous and easy to wash.
3. Nylon is used in many articles; like socks, bags, toothbrush, rope, sneakers, parachute, etc.
4. For the same thickness, a nylon thread is stronger than a steel wire.

Question: Explain different types of plastic and their usages.

Answer: Different types of plastic and their usages are as follows:

Thermoplastic: Some plastics easily get deformed on heating, and can be easily bent and reshaped by heating. They are called thermoplastic. Polythene and PVC are examples of thermoplastic. Thermoplastic is used for making combs, toys, buckets, mugs, etc.

Thermosetting Plastic: Some plastics do not get deformed on heating, and cannot be re-molded into a new shape. Such plastics are called thermosetting plastic. Bakelite and melamine are examples of thermosetting plastic. Bakelite is used for making electrical switches and switchboards because it is a poor conductor of heat and electricity. Melamine is resistant to fire and is hence used for making utensils.

Question: Write some salient features of rayon.

Answer: Some salient features of rayon are as follows:

1. Rayon is similar to silk but is cheaper than silk. Hence, rayon is also called ‘poor man’s silk’.
2. Rayon can be dyed in various colours.
3. Rayon is usually mixed with cotton to make bedsheet and dress materials.

Question: What are the characteristics of synthetic fibres?

Answer: Following are the characteristics of synthetic fibres:

1. They are less expensive.
2. They are readily available.
3. They can be easily washed.
4. They are easy to maintain.

Question: Plastic bags create which kinds of problems?

Answer: Following problems are created by plastic bags:

1. Plastic bag keeps on accumulating in the environment.
2. It chokes drains.
3. A stray animal can die if it accidentally swallows plastic bag.