Question of Exercise 2

Combustion and Flame of Class 8

Question
Asphalt is used for/ as :

Answer

Option 1 aviation fuel

Option 2 making road surface

Option 3 running water pumps

Option 4 dry cleaning of clothes

Frequently Asked Questions

Explain why the following are made of thermosetting plastics

(a) Saucepan handles

(b) Electric plugs/switches/plug boards

Solution:

Explanation:

  • The given substances, i.e. Saucepan handles and Electric plugs/switches/plug boards are made of thermosetting materials, as these are poor heat and electrical conductors.
  • They also don't usually bend or deform.
  • After heating and shaping pressure, thermosetting polymers harden permanently.

 

Final answer:

Hence, (a) Saucepan handles and (b) Electric plugs/switches/plug boards are made of thermosetting plastics because they have poor conduction of electricity and are durable.

 

 

Name two metals which are liquid at room temperature

Solution:

Explanation: 

Metals:

 

  1. Metals have a shiny appearance and are said to be lustrous.
  2. Good conductors of heat and electricity.
  3. Malleable and ductile in nature.
  4. High melting and boiling points.

Final answer:

The metals which are liquid at room temperature are Mercury and Gallium.

 

 

Avoid plastics as far as possible Comment on this advice

 

 

 

Solution:

Explanation: 

Plastic is described as a material that comprises an organic compound with a high molecular weight as an essential element and can also be known as long chain polymers.

Few characteristics of plastics can be mentioned as follows:

  1. Strong in nature
  2. Poor conductor of electricity
  3. Corrosion free

When plastic bags are burned, poisonous gases are generated, and when animals consume them, their respiratory systems are strangled, resulting in death.

Final Answer:

We should avoid using plastics as much as possible because they are non-biodegradable in nature. When they are discharged into the environment, they poison it. 

 

Which of the following is a source of rayon

A: Wool

B: Wood pulp

C: PET

D: Silk

Solution:

Explanation: 

 Rayon is a synthetic fiber. It is obtained from a natural raw material named cellulose.

After chemical treatments, rayon is obtained.The cellulose is extracted from wood pulp.

Therefore, option B. is the correct answer.

Answer: 

Hence the option B Wood pulp i.e is the correct answer.

Why is it said that air is a homogeneous mixture of various gases

Solution:

Explanation:

  • Air is a homogeneous mixture of gases because it is mainly composed of nitrogen and oxygen.
  • Its elements are not easily separated or distinguished from each other.

Final answer:

It is said that air is a homogeneous mixture of various gases because it is mainly composed of nitrogen and oxygen. Its elements are not easily separated or distinguished from each other.

 

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