NCERT Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

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NCERT Solutions for Class 8 Science Chapter 3 Synthetic Fibres and Plastics helps you in knowing the most information about every question so that you can cross-examine yourself and make sure you are successful on your exam day. Each NCERT Solutions is written in a manner that makes it easy for anyone to understand the concepts better.

NCERT Textbook will provide you with a lot of interesting topics to dig into. Chapter 3 CBSE Class 8 Science NCERT Solutions helps students do better and memorize more easily during times of intense pressure.

Chapter 3 Synthetic Fibres and Plastics Class 8 Science NCERT Solutions

1. Explain why some fibres are called synthetic.

Solution

Some fibres are called synthetic because they are made by human beings. The raw materials used for preparing synthetic fibres are petrochemicals.

2. Mark (✔) the correct answer.
Rayon is different from synthetic fibres because:
(a) It has a silk-like appearance.
(b) It is obtained from wood pulp.
(c) Its fibres can also be woven like those of natural fibres.

Solution

(b) It is obtained from wood pulp.

3. Fill in the blanks with appropriate words.
(a) Synthetic fibres are also called ______ or ______ fibres.
(b) Synthetic fibres are synthesised from a raw material called ______.
(c) Like synthetic fibres, plastic is also a ______.

Solution

(a) Man-made, artificial
(c) Polymer
(b) Petrochemicals

4. Give examples which indicate that nylon fibres are very strong.

Solution

Nylon fibres are very strong as it is used for making ropes and used for making parachutes.

5. Explain why plastic containers are favoured for storing food.

Solution

Plastic containers are favoured for storing food because:
(i) Plastic does not react with food, air or water.
(ii) Plastic is strong and light weight.
(iii) Plastic containers come in many different sizes, shapes and colours.
(iv) Plastic provide resistant from bacteria.

6. Explain the difference between thermoplastic and thermosetting plastics.

Solution

ThermoplasticThermosetting plastic
We can bend thermoplastics easily.Thermosetting plastic cannot be easily bent rather break if force is applied.
On heating, it gets deformed.It breaks on bending. Heating has no effect on it.
It can be used again and again.It cannot be reused.
It can be moulded into various shapes on heating.It can be moulded only once on heating.
Examples of thermoplastic include polythene, PVC, etc.Examples of thermosetting plastic include bakelite and melamine.

7. Explain why the following are made of thermosetting plastics.
(a) Saucepan handles
(b) Electric plugs/switches/plug boards

Solution

(a) Saucepan handles are made of thermosetting plastics because thermosetting plastic is a bad conductor of heat and does not deform on heating.
(b) Electric plugs/switches/plug boards are made of thermosetting plastic because thermosetting plastic is a bad conductor of electricity and hence, reduces the risk of an electric shock.

8. Categorise the materials of the following products into ‘can be recycled’ and ‘cannot be recycled’.
Telephone instruments, plastic toys, cooker handles, carry bags, ballpoint pens, plastic bowls, plastic covering on electrical wires, plastic chairs, electrical switches

Solution

Can be recycled: Plastic toys, carry bags, ballpoint pens, plastic bowls, plastic chairs.
Cannot be recycled: Telephone instruments, cooker handles, plastic coverings on electric wires, electrical switches.

9. Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from synthetic materials? Advise Rana, giving your reason.

Solution

Cotton shirts are a great choice for Rana, since they have pores that let air pass through them. Synthetic fabrics, on the other hand, are very tightly woven, which means they do not allow air to pass through. A cotton shirt absorbs sweat and gives a dry feeling, whereas a synthetic shirt has little ability to absorb water.

10. Give examples to show that plastics are non-corrosive in nature.

Solution

Plastics are non-corrosive due to their non-reactivity to water and chemicals. For instance, cleaning chemicals are stored in plastic bottles rather than metal ones at home.

11. Should the handle and bristle of a tooth-brush be made of the same material? Explain your answer.

Solution

Toothbrush handles and bristles cannot be made of the same material since the handle of the toothbrush needs to be hard and strong, while the bristle needs to be soft and flexible.

12. ‘Avoid plastics as far as possible’. Comment on this advice.

Solution

Plastics are a major contributor to environmental pollution, and their production and disposal have had serious consequences for the environment. Plastics are made from non-renewable resources, such as petroleum and natural gas, which means that their production is not sustainable. They also take hundreds of years to decompose, meaning they can linger in the environment for a long time. They release poisonous gases on burning. They are non-biodegradable and hence, pollute soil, water and air. Animals choke on swallowing polythene bags and die. Polythene bags also clog the drains. Therefore, use of plastic should be avoided as far as possible.

13. Match the materials in column A with their characteristics given in column B.

Column AColumn B
(i) Polyester(a) Prepared by using wood pulp
(ii) Teflon(b) Used for making parachutes and stockings
(iii) Rayon(c) Used to make non-stick cookware
(iv) Nylon(d) Fabrics do not wrinkle easily

Solution

Column AColumn B
(i) Polyester(d) Fabrics do not wrinkle easily
(ii) Teflon(c) Used to make non-stick cookware
(iii) Rayon(a) Prepared by using wood pulp
(iv) Nylon(b) Used for making parachutes and stockings

14. ‘Manufacturing synthetic fibres is actually helping in conservation of forests’. Comment.

Solution

Synthetic fibres are made from petroleum-based products and do not require wood or other resources from forests, meaning that fewer trees need to be cut down in order to produce them. This helps reduce deforestation, which is a major cause of habitat loss for many species of wildlife. Also, synthetic fibres are often more durable than fabrics made from natural materials like cotton or wool. This means that they can last longer without needing to be replaced, reducing the demand for new materials and helping conserve resources.

15. Describe an activity to show that thermoplastics are poor conductors of electricity.

Solution

To do this, you will need a battery, small lightbulb, and two pieces of wire. Connect the wires to the ends of the battery and then connect one wire to the base of the light bulb. Then take a piece of thermoplastic material, such as plastic wrap or an empty plastic bottle, and cut it into two pieces. Use one piece to connect the other end of the wire to the top of the light bulb. If all connections are secure, when you turn on the switch, no current should be able to flow through the thermoplastic material and thus no light should be produced from the bulb. This demonstrates that thermoplastics are poor conductors of electricity because they don’t allow for electric current to flow through them easily or effectively.

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