Class 7 NCERT Solutions English Chapter 8 - Fire: Friend and Foe

(i) Early man was frightened of fire.
(ii) Fire is the result of a chemical reaction.

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

The particular temperature at which a fuel begins to burn is called its flash point. It is also known as its kindling temperature.

(i) Some of the common uses of fire are to cook food, warm our 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.

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. 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 from reaching the burning material. Sometimes carbon dioxide is used to extinguishing a fire as 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. 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, the fire is extinguished.

Combines Call Comes
Blow Bursts Gets Means
Stops Absorbs Lowers

(i) Gandhiji's life was devoted to the cause of justice and fair play.
(ii) Have you insured your house against fire?
(iii) Diamond is nothing but carbon in its pure form.
(iv) If you put too much coal on the fire at once you will smother it.
(v) Smoking is said to be the main cause of heart disease.
(vi)  When asked by an ambitious writer whether he should put some fire into his stories, Somerset Maugham murmured, "No, the other way round".
(vii) She is a carbon copy of her mother.
(viii)  It is often difficult to smother a yawn when you listen to a long speech on the value of time.

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.

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.

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.

(i) You were required to keep all the doors open, not shut.
(ii) PUPIL: What mark did I get in yesterday's Maths test?
TEACHER: You got what you get when you add five and five and subtract ten from the total.
(iii) Run four kilometres a day to preserve your health. Run a lot more to destroy it.
(iv) If a doctor advises a lean and lanky patient to reduce his weight further, be sure he is doing it to increase his income.
(v) The world is too much with us; late and soon, Getting and spending we lay waste our powers.

(i) The cat chased the mouse across the lawn.
(ii) We were not allowed to cross the frontier. So we drove along it as far as we could and came back happy.
(iii) The horse went past the winning post and had to be stopped with difficulty.
(iv) It is not difficult to see through your plan. Anyone can see your motive.
(v) Go along the yellow line, then turn left. You will reach the post office in five minutes.