Question 1:
Mark the correct answer in each of the following.
(i) Early man was frightened of
(a) lightning and volcanoes.
(b) the damage caused by them.
(c) fire.
(ii)
(a) Fire is energy.
(b) Fire is heat and light.
(c) Fire is the result of a chemical reaction.
Answer:
(i) Early man was frightened of fire.
(ii) Fire is the result of a chemical reaction.
Question 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.
|
(i) (ii) (iii) (iv) |
(ii) (iii) (i) (iv) |
|
(iv) (iii) (ii) (i) |
(iv) (ii) (iii) (i) |
Answer:
(iv) (ii) (iii) (i)
Question 3:
What do you understand by the ‘flash point’ of a fuel?
Answer:
The temperature at which a fuel begins to burn is called its flash point.
Question 4:
(i) What are some common uses of fire?
(ii) In what sense is it a “bad master”?
Answer:
(i) Some of the common uses of fire are to cook food, warm the homes in winter and to generate electricity.
(ii) It is a “bad master” because if it is not kept under control, it can prove very dangerous. Each year thousands of homes and shops are damaged by fire. Vast areas of forest are also destroyed and hundreds of people are killed or injured.
Question 5:
Match items in Column A with those in Column B.
|
A |
B |
||
| (i)
(ii) (iii) |
fuel
oxygen heat |
–
– – – – – – |
lighted matchstickaircoalburning coal
wood smouldering paper cooking gas |
Answer:
|
A |
B |
||
| (i)
(ii) (iii) |
fuel
oxygen heat |
–
– – |
coal, wood, cooking gasairlighted matchstick, burning coal, smouldering paper |
Question 6
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 7:
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 |
| • it absorbs heat from the burning material and• lowers the temperature.• reduces the risk of fire.• with a damp blanket.
• we heat it before it catches fire. • to put out an electrical fire. |
Answer:
|
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. |
Page No 120:
Question 8:
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 9:
Spraying water is not a good way of putting out an oil fire or an electrical fire. Why not?
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.
Question 10:
What are some of the things you should do to prevent a fire at home and in the school?
Answer:
This question requires you to use your own perspective as well as your analytical skills. The answer to the question would vary from one person to another. It is suggested that you read the text carefully and try attempting it on your own.
