Combustion

• A chemical process in which a substance reacts with oxygen producing heat is called combustion.
• Substances can be classified as combustible or non-combustible, depending on whether or not they can be burnt.

Combustible substance:

• Substances which burn in air to produce heat and light are called combustible substances.
• E.g.:- wood, coal, charcoal, kerosene, petrol, diesel, liquified petroleum gas (LPG), compressed natural gas (CNG) etc.

• Wood is burned in bonfires and fireplaces to produce heat and light.

Non-combustible substances:

• Substances that do not burn in air or oxygen to produce heat and light are called non-combustible substance.
• Water, sand, glass, and cement are examples of non-combustible substances.

Types of Combustion:

• Combustion can be divided into the following three types-

Rapid combustion:

• In this type of combustion, large amount of heat and light are released in a very short span of time.
• Example: Combustion of LPG, which produces heat and light instantly

Explosion: 

• Combustion in which a sudden reaction takes place with the evolution of heat, light, sound and large amount of gas is known as explosion e.g.  Ignition of fire crackers

Fire Crackers

Spontaneous combustion:

• The type of combustion in which a material suddenly bursts into flames without application of any apparent heat is called spontaneous combustion. e.g. spontaneous combustion of coal dust, White phosphorous