8th Science NCERT Chapter 4

Fuels used in homes include cow dung, wood, coal, charcoal, petrol, diesel, compressed natural gas (CNG). Fuels used in trade and industry include coal, wood, petrol, diesel, CNG, etc.

Combustion is a chemical process where a substance reacts with oxygen to give off heat. The substance undergoing combustion is called combustible or a fuel. Combustible materials can be solid, liquid, or gas.

Air is essential for combustion. The candle burned freely when air could enter the chimney, but flickered and produced smoke when air was limited. If air was completely blocked, the flame eventually went out.

Ignition temperature is the lowest temperature at which a substance catches fire. For example, while kerosene oil requires heating to ignite, wood does not catch fire on its own at room temperature.

The head of a safety match contains antimony trisulphide and potassium chlorate. Rubbing the match against a rough surface converts some red phosphorus into white phosphorus, which reacts with potassium chlorate to produce enough heat to ignite antimony trisulphide and start combustion.