FIRE: FRIEND AND FOE

Before you read

Fire is both useful and dangerous. What is fire? How did we discover it? How do we control it?

STORY – FIRE: FRIEND AND FOE

Part I

Early man didn’t know what fire was, but he must have seen the damage it could cause. He must have watched lightning and volcanoes long before he began to use fire himself. Fire was powerful and dangerous, and he was frightened.

Fire may have puzzled early man but we now know that fire is the result of a chemical reaction. When the oxygen in the air combines with carbon and hydrogen in a fuel, a chemical reaction takes place. Energy in the form of heat and light is released in this process. This is what we call fire. Three things are needed to make fire — fuel, oxygen and heat. Wood, coal, cooking gas and petrol are some examples of fuel. Oxygen comes from the air. That is why, when you blow on smouldering paper, it often bursts into flame. The third thing needed to make fire is heat. Fuel and oxygen do not make fire by themselves, or else a newspaper or a stick lying in the open would catch fire on its own. To burn a piece of paper or wood,

we heat it before it catches fire. We generally do it with a lighted match. Every fuel has a particular temperature at which it begins to burn. This temperature is called the ‘flash point’ or ‘kindling temperature’ of the fuel.

It is sometimes said that fire is a good servant but a bad master. It only means that fire is very useful as long as it is kept under control.

Just as three things are needed to start a fire, there are three main ways in which a fire can be put out. In each, one of the three things needed for burning is taken away.

For example, we can take away the fuel. If the fire has no fuel to feed on, no burning can take place. We often let a fire die out simply by not adding more fuel to it.

The second way of putting out a fire is to prevent oxygen from reaching it. No supply of oxygen means no fire. Small fires can be put out or ‘smothered’ with a damp blanket or a sack. This stops oxygen reaching the burning material. Sometimes, carbon dioxide is used to extinguish fire. It does not allow oxygen to reach the burning material.

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. You blow on a burning matchstick or a candle to put it out. In doing so, you remove the hot air around the flame bringing down its temperature below the flash point, and the candle goes out. Sometimes, water is sprayed on a fire. It absorbs heat from the burning fuel and lowers the temperature. The blanket of water also cuts off the supply of oxygen, and the fire is extinguished.

Some fires cannot be put out with water. If water is sprayed onto an oil fire, 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. Water should also not be used on fires caused by electrical appliances. The person spraying water might receive an electric shock and be killed. A carbon dioxide extinguisher is the best thing tofight an electrical fire.

We spend millions of rupees each year in fighting fires. And we spend more trying to find new ways of preventing fires from happening and getting out of control. On the whole, we have learnt rather well to control fire and put it to good use in our everyday life.

Long ago, there were no firemen. When fire broke out, everybody became a firefighter. People formed human chains (they still do if required) and passed buckets of water from a well or a pond to the blaze. Now there are laws about building construction which ensure that space is left between buildings to reduce the fire risk. Every new building, especially a public place, must ensure observance of fire prevention norms. Bands of firefighting workers with special equipment, known as fire brigades, are there to put out fires. Firefighters are highly trained people. They possess many skills. They cut off electricity supply, knock down dangerous walls, spray water and other materials to bring fire under control.

They are also trained in first aid so that they can help people suffering from burns or from the effects of smoke.

The discovery of fire and its uses helped early man to cope with nature better and gradually adopt a settled mode of life. Fire is still worshipped in many parts of the world. Fire is indeed a friend but, as we know, it can be a dangerous enemy once it gets out of control.

Oral Comprehension Check

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

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

a) (i) (ii) (iii) (iv)

b) (ii) (iii) (i) (iv)

c) (iv) (iii) (ii) (i)

d) (iv) (ii) (iii) (i)

Source: This topic is taken from NCERT TEXTBOOK