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Question 1

Explain why some fibres are called synthetic

Solution:
Some fibres are called synthetic because they are made by human beings

 

Question 2

Give examples which indicate that nylon fibres are very strong

Solution:
Parachutes and ropes for rock climbing

 

Question 3

Explain why plastic containers are favored for storing food

Solution:
Three main advantages of using plastic containers for storing food are:

i. They do not react with food items

ii. They do not get rusted

iii. They are light, strong and durable
 

Question 4

Explain the difference between the thermoplastic and thermosetting plastics

Solution:
Thermoplastics can be softened by heating and can be bent easily whereas thermosetting plastics cannot be softened by heating and break when forced to bend

 

Question 5

Explain why the following are made of thermosetting plastics

a. saucepan handles b. electric plugs / switches / plug boards

Solution:
Above articles are made up of bakelite (a thermosetting plastic) because it is

i. poor conductor of electricity ii. heat resistant
 

Question 6

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 Cannot be recycled
Toys, carry bags, plastic bowls, electric wire covering plastic chairs Telephone instruments, cooker handles, ball point pens, electrical switches


Question 7

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

Solution:
Synthetic fabric soaks less water than cotton fabric. In summers we have extensive sweating which must be soaked up by our clothing. Since synthetic fabric is poor in this property we prefer cotton clothes in summers


Question 8

Give examples to show that plastics are noncorrosive in nature

Solution:
i. It does not react with the chemical or other items store in the containers made of it

ii. It does not get rusted when exposed to moisture and air

iii. It does not decompose when left in open for a long period
 

Question 9

Should handle and bristle of a tooth brush be made of the same material. Explain you answer

Solution:
Handle and bristles of a tooth brush should be made of different materials because they have different uses and require different properties in the material e.g., bristles should be much more flexible than the handle

 

Question 10

‘Avoid plastics as far as possible" comment on this advice

Solution:
Since plastics are generally non-biodegradable it therefore takes several years to decompose and so it is not environment friendly. It causes environmental pollution .When the synthetic material is burnt it takes a long time to get completely burnt. In the process it releases a lot of poisonous fumes into the atmosphere causing air pollution.

 

Question 11

"Manufacturing synthetic fibres is actually helping conservation of forests" comment.

Solution:
In the manufacture of synthetic fibres we use no material from natural sources thus in turn we conserve forests which may otherwise be destroyed. When we use articles made of plastics we also save thousands of trees which otherwise have to be cut if we used articles made of wood or natural fibres.

 

Question 12

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

Solution:
A thermoplastic (or plastic) is poor conductor of electricity it can be shown by using a plastic wire as a connecting wire in a circuit. In this conditions the bulb will not glow




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