Give two examples each for solid, liquid and gases fuel along with some important use.

Hint: Fuel can be defined as a substance or material, which on combustion produces heat. Wood, LPG, Kerosene, coal, petrol, natural gas, diesel, biogas etc. are some fuels used in our daily lives. Different types of fuel produce different amounts of heat on combustion or on burning.

Complete step by step answer:
We all use LPG, Kerosene, coal, petrol, natural gas, diesel, biogas in our daily lives. The heat energy that is produced by the combustion or burning of fuel can be used to cook food, running factory machines and motor vehicles and can be converted to electrical energy.
Based on state, fuels can be classified into three categories as solid fuels, liquid fuels and gaseous fuels.
Solid fuel: Coal and wood are solid fuels. Coal is used in industries and factories while wood is used mostly in homes.
Liquid fuel: kerosene and petrol are liquid fuels. Kerosene is used in stoves to cook food while petrol is used in vehicles.
Gaseous fuel: CNG and LPG are gaseous fuels. LPG is used in homes and in vehicles while CNG is used to drive vehicles.
Ideal fuel should have high calorific value, burn easily at moderate rate in air, must have proper ignition temperature, should not produce harmful gases on combustion, fuel should be cheap, easy to transport etc.

Note:
The amount of heat that is produced by the complete combustion or burning of 1 kg of fuel is termed as its calorific value expressed in kilojoules per kilogram. The calorific value for kerosene is 45,000 KJ/Kg which means 1kg kerosene is completely burned, it produces 45,000 KJ of heat.