ch 8 fire friend and foe class 7 what i found challenging
Answers
Explanation:
Early man didn’t know what fire was. However, they must have seen the damage caused by the bolts of lightning and the volcano eruptions. Since he didn’t know what fire was and hadn’t discovered the uses of it, he was frightened by the damage caused by this unknown thing. Then the writer tells us that fire had confused the early man, but we now know what fire is. Fire is the result of a chemical reaction. When oxygen gas reacts with hydrogen and carbon in the form of a fuel, energy is released in the form of heat and light. This is known as fire. Hence, we know that three things are required for the making of fire – heat, fuel and oxygen. Fuel can be in the form of petrol, wood, coal or cooking gas. Oxygen can be found in free air. Hence, the requirement of oxygen can be met quite easily. For example, when we blow on a smouldering piece of paper, the paper catches fire. The last requirement is heat. If heat would not have been a requirement, then a newspaper lying anywhere could also burst into flames. To make the wood catch fire, we heat it. This is often done with a lighted matchstick. Now, we have to wait for some time for the wood to catch fire. This is because every fuel has a particular temperature at which it begins to burn. So, we have to wait for the wood to reach that particular temperature, and that temperature would be wood’s ‘flash point’ or ‘kindling temperature’. Then, the writer tells us that it is sometimes said that fire is a good servant but a bad master. It means that fire is useful only when it is kept under control. The writer then takes an example of fire being useful for cooking, keeping us warm in winters and generating electricity until it goes out of control and burns down our house. Each year thousands of homes and shops are damaged by fire due to this reason. Vast areas of forest are also destroyed and hundreds of people are killed or injured. Then, the writer tells us that the number of ways to put out fire are also three. In each way, one of the requirements is taken from the fire, which extinguishes it. The first way is to take away the fuel. By taking away the fuel, fire will not have a substance to burn on, so it will get extinguished. The second way of putting out a fire is to prevent oxygen from reaching it. If we block oxygen and prevent it from reaching the burning substance, it will eventually extinguish the fire. Oxygen is a gas which supports burning. No supply of oxygen means no 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. To do so, we usually use water. However, not all fires can be brought down with buckets of water. Such fires are the fires caused by oil and electric appliances. If we use water onto an oil fire, the oil fire will float on the water because of the oil in it. In fact, the water can spread the oil fire even more, which will result in more damage. If a person tries to put out an electric fire with water, the person will receive an electric shock, which can even kill the person. The correct way is to use fire extinguishers which have carbon dioxide. The writer then tells us that we spend millions of rupees each year in fighting fires. Also, we spend millions of rupees each year to find new ways of preventing fires from happening and also keeping them under control. Because of this, we have found good ways to control fire and put it to good use in our everyday life. The writer then tells us about the olden times, when there were no firemen. People themselves were firemen. They would form a human chain which would start from the burning building to a well or a pond. With buckets, the water would get transported from one person to another then onto the fire. However, things have changed. Now there are laws about building construction which ensure that space is left between buildings to reduce the risk of spreading of fire. 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 skilled and brave people. They possess many skills. They cut off electricity supply, knock down dangerous walls, spray water and other materials to bring fire under control. Also, they are trained in providing First Aid so that they can help the injured people. The discovery of fire and its uses have been very useful for the settled mode of life. Fire is worshipped in some places, who believe that worshipping fire will keep them safe. We should never forget: fire is a friend but a foe when gone out of control
Answer:
If a fire starts somewhere, it becomes difficult not to extinguish it and one should not play with fire.