NCERT Book Class 7 English 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?

Fire: Friend and Foe

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. For instance, we use it to cook our food, warm our homes in winter and to generate electricity. But, on the other hand, if fire gets out of control it can be 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.

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.

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.

Working with the Text

Answer the following questions.

1. What do you understand by the ‘flash point’ of a fuel?

2. (i) What are some common uses of fire?

(ii) In what sense is it a “bad master”?

Please refer to attached file for NCERT Class 7 English Fire - Friend and Foe