Lakhmir Singh & Manjit Kaur: Synthetic Fibers And Plastics- 1 | Lakhmir Singh & Manjit Kaur Solutions: Class 8 Science PDF Download

Q.1. Name the units of which cellulose polymer is made.

Cellulose polymer is made from the repeat units of the monomer glucose.

Q.2. Name the man-made fibre prepared from natural materials.

Rayon is the man-made fibre prepared from the natural materials.

Q.3. Name the man-made fibre which is regarded as artificial silk.

Rayon is the man-made fibre which is regarded as artificial silk.

Q.4. Name the fibre obtained by the chemical treatment of wood pulp (or cellulose).

Rayon is obtained by the chemical treatment of wood pulp or cellulose.

Q.5. Name the first fully synthetic fibre.

Nylon is the first fully synthetic fibre. It was prepared from coal, water and air.

Q.6. Name the fibre used for making parachutes and rock climbing ropes.

Nylon is used for making parachutes and rock climbing ropes.

Q.7. Which synthetic fibre contains the organic group similar-to those which give fruits their sweet smell.

Polyester is the synthetic fibre which contains the organic group similar-to those which give fruits their sweet smell.

Q.8. Which synthetic fibre feels like wool and used as a substitute for wool?

Acrylic is the synthetic fibre feels like wool and used as a substitute for wool.

Q.9. To which kind of synthetic fibres does terylene belong?

Terylene is a kind of a polyester.

Q.10. State one disadvantage of using synthetic fibres for making clothes.

Synthetic fibres are different from the natural fibres. They melt on heating. If the clothes made of synthetic fibres catch fire, it can be very dangerous. The fabric will melt and can stick to the body of the person wearing it. Hence, we should not wear synthetic clothes while working in a kitchen or working in a laboratory.

Q.11. Name the form of polyester which is replacing materials like glass and used for making bottles and jars.

PET is a very familiar form of polyester. It is used for making bottles and utensils which is replacing materials like glass.

Q.12. Name four different plastics.

Polythene, PVC- Poly vinyl chloride, bakelite and melamine are the examples of different plastics.

Q.13. Give one use of Teflon.

Teflon is used for nonstick coating on cookware. It is a special plastic on which oil and water do not stick.

Q.14. Which of the two is a thermosetting plastic: PVC or bakelite?

The plastics which cannot be softened by heating, when moulded once are called thermosetting plastics. Bakelite is a thermosetting plastic.

Q.15. Fill in the following blanks with suitable words:
(a) Synthetic fibres are also called ______ or ______ fibres.
(b) Synthetic fibres are made from raw materials called ______
(c) Like synthetic fibres, plastic is also a ______
(d) The use of plastics can be reduced by using bags made of ______ or ______ instead of polythene bags.

(a) man-made or artificial, Rayon and nylon are the examples of synthetic fibers.

(b) petrochemicals, Nylon was the first fully synthetic fiber. It was petrochemicals which is derived from fossil fuels

(c) polymer , The arrangement of units in a plastic can be linear or cross-linked.

(d) paper or jute bag Disposal of plastic is a major problem. This is can be reduced by use paper or jute bag.

Q.16. What is a polymer? Name the natural polymer from which cotton is made.

A synthetic fibre is made of small units which are joined together. These units are made of chemical substances. Such small units combine to form a large single unit called a polymer. Hence, a polymer is made of many repeating units. Polymers also occur in nature. For example, cotton is a natural polymer which is made from the cellulose. Cellulose is made up of a large number of glucose units.

Q.17. State the characteristics of synthetic fibres.

A synthetic fibre is made of small units which are joined together. These units are made of chemical substances. Such small units combine to form a large single unit called a polymer. Hence, a polymer is made of many repeating units. Following are the characteristics of synthetic fibres:

• Synthetic fibres absorb very less water and they dry up quickly.
• They are durable and are less expensive.
• They are readily available and are easy to maintain.
• Due to such unique properties, synthetic fibres are used to make dress materials.

Q.18. What is nylon? State the important properties of nylon.

Nylon is the first fully synthetic fibre. It was made in 1931, without the use of any natural raw material from plants or animals. It was prepared from coal, water and air. Following are the properties of nylon:

• Nylon has the ability to show variation of luster. It has the ability to be very lustrous, semi lustrous or dull.
• It is highly durable and is used for making seatbelts and tire cords.
• Nylon fibre is very strong, elastic and light. It is lustrous and easy to wash. Hence, it became very popular for making clothes.
• A nylon thread is actually very strong than steel wire. It is also used for making parachutes and ropes for rock climbing.
• It is also used for making articles such as socks, ropes, tents, toothbrushes, car seat belts, sleeping bags and curtains.

Q.19. Give the important uses of nylon.

Nylon is the first fully synthetic fibre. Nylon is the first fully synthetic fibre. Following are the uses of nylon:

• It is highly durable and is used for making seatbelts and tire cords.
• Nylon fibres is very strong, elastic and light. It is lustrous and easy to wash. Hence, it became very popular for making clothes.
• A nylon thread is actually very strong than steel wire. It is also used for making parachutes and ropes for rock climbing.
• It is also used for making articles such as socks, ropes, tents, toothbrushes, car seat belts, sleeping bags and curtains.

Q.20. What is polyester? Name a popular polyester.

Polyester is the synthetic fibre which is made up of repeating units of a chemical called an ester. Esters are the chemicals which give fruits their smell. Polycot, poly wool and terry cot are popular polyesters. These are made by mixing two types of fibres. For example, polycot is a mixture of polyester and cotton. Poly wool is a mixture of polyester and wool. Fabrics made from polyester does not get wrinkled easily. It remains crisp and easy to wash. Hence, it is suitable for making dress material.