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

NCERT Solutions for Class 8 Science Chapter 3 - Synthetic Fibres and Plastics by Jagran Josh will help you find accurate and simple answers to all questions given in the chapter.

Created On: Jun 9, 2021 20:57 IST
NCERT Solutions for Class 8 Science Chapter 3
NCERT Solutions for Class 8 Science Chapter 3

We are providing here the best NCERT Solutions for Class 8 Science Chapter 3 - Synthetic Fibres and Plastics. Students can read as well as download these NCERT Solutions and refer to them for making effortless preparations for their Science exam. We have provided here the NCERT Solutions for Science chapter 3 of the latest NCERT Book for Class 8 Science. Check the most accurate NCERT Solutions to clear the concepts and do well in the subject.

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

Exercises

1. Explain why some fibres are called synthetic.

Answer:

Some fibres are called synthetic fibres because they are made by man using different types of chemicals.

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..

Answer: (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 raw materials called ________.
(c) Like synthetic fibres, plastic is also a _________.

Answer:

(a) Synthetic fibres are also called artificial or man-made fibres.
(b) Synthetic fibres are synthesised from raw materials called petrochemicals.
(c) Like synthetic fibres, plastic is also a polymer.

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

Answer:

Examples which indicate that nylon fibres are very strong are:

→ Nylon is used in making ropes for rock climbing.

→ Nylon is used in making parachutes.

→ Nylon is used in making seat belts.

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

Answer:

Plastic containers are favoured for storing food due their following properties:
→ The plastics are non-reactive so they do not get corroded.

→ The plastics do not react with the food stored in them.

→ They are light weight and have good strength.

→ They are cheap and easy to handle.

6. Explain the difference between thermoplastic and thermosetting plastics.

Answer:

Difference between thermoplastic and thermosetting plastics:

Thermoplastic

Thermosetting plastic

The plastic which gets softened on heating and can be bent easily is known as thermoplastic.

 

The plastic that cannot be softened on heating is known as thermosetting plastic. It may break when forced to bend.

It can be molded and reshaped easily.

It cannot be molded and reshaped easily.

Examples: Polythene and PVC

Examples: Bakelite and Melamine

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

Answer:

(a) The saucepan handles are made of thermosetting plastics because they are bad conductors of heat. So they do not get heated up while cooking and can be handled easily. In addition to this, thermosetting plastics do not get softened on heating.

(b) Electrical plugs, switches and plug-boards are made up of thermosetting plastics because they are bad conductors of electricity. So, they do not allow the electric current to pass through them are thus safe to touch.

8. Categorize the materials of the following products into 'can be recycled' and 'cannot be recycled'.
Telephone instruments, plastic toys, cooker handles, carry bags, ball point pens, plastic bowls, plastic covering on electrical wires, plastic chairs, electrical switches.

Answer:

can be recycled

cannot be recycled

plastic toys, carry bags, plastic bowls, plastic covering on electrical wires, plastic chairs

telephone instruments, cooker handles, ball point pens electrical switches

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

Answer:

Rana should buy shirts made from cotton because it is a good absorber of water. Therefore, it can soak the sweat coming out of our body and give relief from extreme heat.

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

Answer:

Some examples to show that plastics are non-corrosive in nature are:

→ Plastics do not react with water and air.

→ They do react with the chemicals stored in the plastic bottles.

→ Plastics do not react with the food items stored in them.

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

Answer:

No, the handle and bristles of a tooth brush should not be made of the same materials. The handle of a toothbrush should be the handles should be made up of hard and strong material so that it can give a firm grip. On the other hand, the bristles should be made up of soft and flexible material so that they do not hurt our gums.

12. 'Avoid plastics as far as possible'. Comment on this advice.

Answer:

Plastics are non-biodegradable materials which means they do not get decomposed. They lead to air pollution as on burning they release poisonous gases into the atmosphere. Also, the plastic bags thrown in garbage if swallowed by animals can choke their respiratory system and even lead to their death. Plastics bags thrown carelessly can also cause clogging of the drains.

13. Match the terms of column A correctly with the phrases given in column B.

A

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

Answer:

A

B

(i) Polyester

(a) Fabrics do not wrinkle easily

(ii) Teflon

(b) Used to make non-stick cookware

(iii) Rayon

(c) Prepared by using wood pulp

(iv) Nylon

(d) Used for making parachutes and stockings

14. 'Manufacturing synthetic fibres is actually helping conservation of forests'. Comment.

Answer:

Natural fibres like cotton, silk, wool and jute are obtained from plants and animals, whereas synthetic fibres are obtained from petrochemicals. Thus, the manufacturing of synthetic fibres has reduced the cutting of trees or hunting of animals. In this way manufacturing synthetic fibres is actually helping conservation forests.

15. Describe an activity to show that thermoplastic is a poor conductor of electricity.

Answer:

The following activity can show that thermoplastic is a poor conductor of electricity:

We will design a circuit to show that thermoplastics are poor conductors of electricity.

→ For this activity, take a bulb, wires, a battery, a piece of metal, and a plastic pipe.

→ Make two circuits - one with the metal and other with the plastic pipe as shown in the following diagrams.

→ After switching on the circuit, you will observe that the bulb in the circuit with metal starts glowing whereas in the other circuit with plastic pipe bulb does not glow.

→ This proves that the plastic pipe which is a thermoplastic is a poor conductor of electricity.

Download NCERT Solutions for Class 8 Science Chapter 3 in PDF

Also check the NCERT Books and NCERT Solutions for all major subjects of Class 8:

NCERT Books for All Subjects of Class 8 (Latest Editions for 2021-2022)

NCERT Solutions for All Subjects of Class 8 (Updated for 2021-2022)

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  • Abhishek dwivediJul 10, 2021
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