What is combustion ?
What is combustion? Burning of a substance is called combustion. When you light a matchstick, the combustion of phosphorus at the tip takes place which then burns the matchstick. When you light a candle, the combustion of wax begins and when you burn a paper, the combustion of paper takes place.
Combustion of substances is useful in many ways. Your body obtains energy by burning glucose with the help of oxygen. This process is known as cellular respiration. It occurs inside every living cell of your body. Combustion of fuels helps us to cook food. It also moves motor vehicles and machines. Combustion of coal helps us to generate electricity. Without combustion, most industries would not be able to operate. Combustion is a chemical reaction between a combustible substance and oxygen. Three things are required for the process of combustion to start-a combustible substance, oxygen and ignition temperature.
What is a combustible substance?
Substances that can burn easily are called combustible substances. Paper, cloth, candle, cooking gas, wood and dry leaves are materials made up of combustible substances. You cannot start a fire without a combustible substance. All substances are not combustible. Water, for example, is not a combustible substance.
Why does combustion need oxygen?
Combustion is a chemical reaction between a combustible substance and oxygen. That is why oxygen is essential for the combustion of a substance. A combustible substance will not burn in the absence of oxygen. If you cover a lighted candle with a container, it stops burning. This is because a lighted candle uses oxygen from the air. When the candle is covered, the supply of oxygen stops and the candle extinguishes.
Take some spirit in a small glass bowl. Make a cotton wick and soak it in the spirit. Place the wick in the glass bowl and light it. Try extinguishing the flame by blowing hard at it. Note what happens. Then place an empty matchbox on the bowl. Does the fire extinguish at once? Why?
Combustion can be complete or incomplete
Combustion of a substance will continue till it receives a supply of oxygen. The moment the supply of oxyg supply of oxygen is inadequate, then the combustion will be incomplete. On the other hand, if the supply of oxygen is adequate, the substance stops, the combustion stops. If the will burn completely. This is known as complete combustion. Incomplete combustion of fuels like kerosene, diesel and petrol produces many pollutants while complete combustion is less polluting.