Question

D. State whether the statements given below are true or false :
1. Air is not necessary for combustion.
2. Ignition temperature is the highest temperature at which a substance catch fire,
3. Carbon dioxide is used as fire extinguisher.
4. Inflammable substances have very low ignition temperature and can easily catch fire
5. LPG is not inflammable.
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eacher's Remark:
32 Workbook Science Class-VIII​

Answer 1

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1. Air is not necessary for combustion.

• This statement is false.

Air is a necessary component for combustion. Without air no combustion will take place. Oxygen is basic necessity.

2. Ignition temperature is the highest temperature at which a substance catch fire.

• This statement is false.

Ignition temperature is tye minimum temperature at which a substance catches fire.

3. Carbon dioxide is used as fire extinguisher.

• This statement is true.

Carbon dioxide is used as fire extinguisher. Carbon dioxide extinguishers are filled with non-flammable carbon dioxide gas.

4. Inflammable substances have very low ignition temperature and can easily catch fire.

• This statement is true.

Inflammable substances have very low ignition temperature and can easily catch fire. Examples of inflammable substances are petrol, alcohol, Liquified Petroleum Gas (LPG), etc.

5. LPG is not inflammable.

• This statement is false.

Inflammable substances have very low ignition temperature and can easily catch fire. LPG is inflammable.

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Answer 2

Answer:

1. False.

2.False.

3.True.

4.True.

5.false.

Explanation:

1.Three things are required in proper combination before ignition and combustion can take place---Heat, Oxygen and Fuel. There must be Fuel to burn. There must be Air to supply oxygen.

2.ignition temperature is the minimum temperature at which a substance catches fire.

3.Carbon dioxide extinguishes work by displacing oxygen, or taking away the oxygen element of the fire triangle. The carbon dioxide is also very cold as it comes out of the extinguisher, so it cools the fuel as well.

4.The substances which have very low ignition temperature and can easily catch fire with a flame are called inflammable substances. Examples of inflammable substances are petrol, alcohol, Liquified Petroleum Gas (LPG), etc.

5.charcoal is not an inflammable substance. . LPG, petrol, and alcohol are some examples of inflammable substances. Hence, one should be very careful when using these substances.