Answer following questions in short.
Q1) What do you understand by the ‘flash point’ of a fuel?
Ans1) The Flash point or kindling temperature of the fuel is the temperature at which fuel like paper, coal or wood begins to burn.
Q2) What are some common uses of fire?
Ans2) The common uses of fire are to cook food, warm our homes in winter and to generate electricity.
Q3) In what sense is fire a “bad master”?
Ans3) Fire a bad master if it gets out of control. It can burn homes, shops and vast areas of forests. It can also kill and injure hundreds of people every year.
Q4) What are the three main ways in which a fire can be controlled or put out?
Ans4) The three main ways in which a fire can be controlled or put out are based on taking away one of the three things needed for burning
a) stop supply of fuel..
b) Prevent oxygen from reaching it. This can be done by throwing a damp blanket or spraying carbon dioxide or sand.
c) Bring down the temperature below the flash point.
Q5) Why does a burning candle go out when you blow on it?
Ans5) We remove the hot air around the flame when we blow on a burning candle. This brings down its temperature below the flash point and candle goes out.
Q6) Spraying water is not a good way of putting out an oil fire or an electrical fire? Why not ?
Ans6) Oil is lighter than water and floats to the top of water. Hence oil fire cannot be put out by spraying water on it. In fact the fire spreads as water can flow quickly carrying the burning oil. Similarly water should not be used on electrical fire. Water is good conductor of electricity. The person spraying water can get electric shock.
Q7) Why was early man frightened of fire?
Ans7) Early man was frightened of fir because it was powerful and dangerous. He was not able to control it.
Q8) Which is the best thing to put out on electrical fire?
Ans8) The best thing to put out on electrical fire is a carbon extinguisher.
Q9) Fire is a good servant but a bad master. Elaborate?
Ans9) Fire is a good servant. It has a number of uses. It cooks our food, warms our homes in winter and produces electricity. But it is a bad master if it gets out of control. Then it burns our houses and forests, it kills and injures hundreds of people.