Class 7 ncert honeycomb chapter 8 summery in points
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Early man must have found fire to be dangerous and frightening. Fire must have been a mystery for an early man but it is known today that it is a result of chemical reaction. When oxygen present in air combines with carbon and hydrogen present in a fuel, energy is released in form of heat and light and this is what fire is. To make fire fuel, heat and oxygen is needed. Wood, coal, gas are fuel, oxygen is available in air. But to cause fire heat is essential. A piece of paper doesn’t catch fire until that is supplied to it. Every fuel burns at a particular temperature which is also called ‘flash point or kindling temperature.
Fire : A Friend and a Dangerous Enemy
Fire is a boon if it is kept under control but can be dangerous if it goes out of it. It is used in our house daily for cooking food, burning candles and so on, but if it goes out of control it can cause damage to life, houses and even forests. Fire can be controlled by taking away any three of the things required for burning it. It can be stopped immediately by taking away the fuel.
It can also be controlled by cutting the oxygen supply, for this many a times blankets are thrown over burning objects. Another way is to reduce the flash temperature; this can be done by spraying water which lowers down the temperature. However, water cannot be used to put out on electrical fires or an oil fire. Carbon dioxide extinguisher is the best way to control electrical fire.
Firefighters:
Earlier people used to form human chains and pass buckets of water from ponds or wells to the blaze. These days, there are trained personnel to handle this. The trained team of firefighters is called fire brigade. They are skilled people to handle all kind of fire. They have the knowledge of first-aid as well and are able to provide immediate help to people suffering from burn injuries or from the effect of the smoke. Discovery of fire has been a great boon to mankind. Fire is worshipped as God in many cultures around the globe. It is a dear friend if can be used properly, but can turn dangerous if it goes out of control.
Explanation:
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