Question

Define: combustion, calorific value of a fueal​

Answer 1

Answer:

Combustion is a chemical process in which a substance reacts rapidly with oxygen and gives off heat

Calorific value is the amount of energy released or produced when 1 kg of fuel burns or any other substance is burnt in the presence of oxygen and the products of combustion are cooled to STP.

Answer 2

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1. Combustion:-

• A chemical process in which a substance reacts with oxygen to produce heat and light is known as combustion.
• Coal, Petrol, Diesel, Kerosene, LPG, CNG are some of the fuels that are burnt and they produce heat and light.

Types of combustion:-

There are three types of combustion.

1. Rapid Combustion
2. Spontaneous combustion
3. Explosion

1. Rapid Combustion:-

• It is the combustion which releases heat and light in a short time.
• Eg: Burning of LPG, Petrol, etc.

2. Spontaneous Combustion:-

• It is the combustion in which the substance catches fire without any external source.
• Eg: Forest Fire

3. Explosion:-

• When combustion is accompanied by huge amount of sound with heat and light, it is called explosion.
• Eg: Burning of fire crackers

2. Calorific Value:-

• The amount of heat produces on 1kg of fuel is known as calorific value.
• It is measured in KJ/kg (Kilo Joule/ Kilogram)

Calorific value of some fuels are:-

1. Wood - 17000-22000
2. Coal - 25000-35000
3. Petrol - 45000
4. CNG - 50000

Although wood has a very high calorific value, bit still discourage it to use as a fuel. Why?

Answer:- Wood is not a clean fuel.

• Burning of wood causes air pollution.
• Burning of wood causes deforestation.