Q.1: Mark the correct answer in each of the following:
i) Early man was frightened of _____________.
ii) Ans: Fire is the result of a chemical reaction.
Q.2: From the boxes given below choose the one with the correct order of the following sentences:
i) That is fire.
ii) A chemical reaction takes place.
iii) Energy in the form of heat and light is released.
iv) Oxygen combines with carbon and hydrogen.
Ans: vi, ii, iii, i
Working With The Text
Answer the following questions:
Q.1: What do you understand by the ‘flash point’ of a fuel ?
Ans: The ‘Flash point’ of a fuel is the temperature at which it begins to burn.
Q.2: i) What are some common uses of fire ?
Ans: Fire is used to cook food, warm our houses in winter and to generate electricity.
ii) In what sense is it a “bad master” ?
Ans: Fire can be a bad master if it gets out of control.
Q.3: Match items in Column A with those in Column B:
|Column A||Column B|
|i) fuel||coal, wood, cooking gas|
|iii) heat||lighted matchstick, smouldering paper, burning coal|
Q.4: What are the three main ways in which a fire can be controlled or put out ?
Ans: The main three ways to control or put out a fire are:
- By taking away the fuel.
- By preventing oxygen from reaching fire.
- By removing the heat.
Q.5: Match the items in Box A with those in Box B:
|Box A||Box 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 the 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|
Q.6: Why does a burning candle go out when you blow on it ?
Ans: When we blow on a burning candle, we remove the hot air around the flame by bringing down its temperature below the flash point, as a result the burning candle goes out.
Q.7: Spraying water is not a good way of putting out an oil fire or an electrical fire. Why not ?
Ans: If water is sprayed onto an oil fire, the oil will float to the top of 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. The spraying of water on an electrical fire might give that person an electric shock. Due to these reasons, it is not advisable to spray water to put out an oil fire or an electrical fire.
Q.8: What are some of the things you should do to prevent a fire at home and in the school ?
Ans: Some of the things that we should do in order to prevent a fire at home and in the school are:
- Not to touch electrical appliances with wet hand.
- Not to put out an electrical fire with water.
- Not to play with electrical appliances.
- Not to touch loose or uncovered wires.
- Use fire extinguisher in case of fire.
- Not to play with burning fire.
- Turn off the gas stove properly and check for gas leakages.
- Not to play with electrical switches.