NCERT Class 7 English Solutions: Fire: Friend and Foe Chapter 8– Part 2

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Question 4:

What are the three main ways in which a fire can be controlled or put out?

Answer:

  • Fire can be controlled or put out by taking away one of the three things required for burning.

  • The first way is to take away the fuel. If the fire has no fuel to feed on, no burning can take place.

  • The second way is to prevent oxygen from reaching it. Small fires can be put out with a damp blanket or a sack. This stops oxygen from reaching the burning material. Sometimes carbon dioxide is used for extinguishing fire.

  • The third way of putting out a fire is to remove the heat. If the temperature can be brought down below the flash point, the fuel stops burning. Blowing on a burning matchstick or a candle removes the hot air around the flame, bringing down its temperature below the flash point. Sometimes water is sprayed on a fire. It absorbs heat from the burning fuel and lowers the temperature. It also cuts off the supply of oxygen, and therefore, fire is extinguished.

Question 5:

Match the items in Box A with those in Box B

A

(i) To burn paper or a piece of wood,

(ii) Small fires can be put out

(iii) When water is spread on fire,

(iv) A carbon dioxide extinguisher is the best thing

(v) Space left between buildings

B

1. It absorbs heat from the burning material and

2. Lowers the temperature.

3. Reduces the risk of fire.

4. With a damp blanket.

5. We heat it before it catches fire.

6. To put out an electrical fire.

Answer:

Match the List
Match the list

A

B

(i) To burn paper or a piece of wood,

We heat it before it catches fire.

(ii) Small fires can be put out

With a damp blanket.

(iii) When water is spread on fire,

It absorbs heat from the burning material and lowers the temperature.

(iv) A carbon dioxide extinguisher is the best thing

To put out an electrical fire.

(v) Space left between buildings

Reduces the risk of fire.

Question 6:

Why does a burning candle go out when you blow on it?

Answer:

A burning candle goes out when we blow on it because blowing removes the hot air around the flame, bringing down its temperature below the flash point.

Question 7:

Spraying water is not a good way of putting out an oil fire or an electrical fire. Why not?

Spraying water

Spraying Water

Answer:

  • If water is sprayed onto an oil fire, then the oil will float to the top of the water and continue to burn. This can be very dangerous because water can flow quickly, carrying the burning oil with it and spreading the fire.

  • In case of an electrical fire, the person spraying water might receive an electric shock and be killed. Therefore, spraying water is not a good way of putting out an oil fire or an electrical fire.

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