Question

How are fuels classified? Give two examples of each?

Answer 1

Hint: Fuel is any material that on reaction with any substance releases energy as heat energy or the material can be used for work. In other words, we can say any substance which on combustion produces a usable amount of energy is known as fuel.

Complete step by step answer:
Generally, fuels can be classified into two factors:
Based on their physical state, i.e. based on the state they are available in nature. These are further classified into three states shown below:
-Solid fuel: These are found in their solid state at room temperature, for example, coal, wood, etc. Solid fuels are easy to transport and store and also have a low production cost. But in the case of solid fuel, there is a large wastage of energy. Their cost of handling is also high.
-Liquid fuel: They are found in their liquid state at room temperature and they are mostly derived from the fossilized remains of dead plants and animals. They have a high calorific value per unit mass and burn without ash. But the cost of liquid fuel is higher as compared to solid fuels and examples of liquid fuel are coal tar, petroleum, alcohol, etc
-Gaseous fuel: This type of fuel occurs in nature, besides being manufactured from solid and liquid fuels. They require a large storage tank and are clean after use. Example of gaseous fuels are coal gas, producer gas, oil gas, etc
-Based on their occurrence they are classified as natural and artificial fuel. Wood, natural gas and petroleum are the example of natural fuel whereas coal tar, producer gas tanbark are the example of artificial fuels.

Note: The energy produced by the combustion of one kilogram of fuel is known as its calorific value. Thus we can differentiate different fuels based on their calorific value for their efficient usage. The fuel which burns at a moderate rate in air and gives large calorific value and also shouldn't affect the environment is known as ideal fuel.