Page 41 - Genius Kidz Prudence Learning Sc-8

FUEL leaving any residue behind.

Definition : Any combustible substance that (vi) Its ignition temperature is low but above
produces heat and light energy on burning is the normal room temperature.
called a fuel. Examples include natural gas, (vii) Its rate of burning is moderate. Gaseous
biogas, kerosene, LPG, charcoal, cow dung, fuel is considered to fulfil maximum of
etc. above mentioned criteria, so it is

Characteristics of a good fuel considered as the best fuel.
A substance is a good fuel if : Calorific Value :

Calorific value decides the efficiency of a fuel
Amount of heat released by complete
combustion of 1 kg of a fuel is called its calorific
value.

Calorific value is expressed as kJ/kg
(kilojoule/kilogram).

Activity 2
Investigate about the calorific value of fuels mentioned below :

Fuel Calorific Value
(a) Methane ______________________
(b) Coal ______________________
(c) Coke ______________________

(d) LPG ______________________
(e) CNG ______________________
(f) Diesel ______________________
(g) Hydrogen ______________________

Classification of fuels (iii) Gaseous fuel : Fuel in gaseous state at

(1) On the basis of their physical state fuels room temperature is known as gaseous
can be : fuel, for example, biogas, water gas,
natural gas.
(i) Solid fuel : Fuel in solid state at room
temperature is solid fuel, for examples (2) On the basis of their source of origin fuels

wood, coal, coke, animal dung, etc. can be of two types :

(ii) Liquid fuel : Fuel in liquid state at room (i) Natural fuels : Fuels that are present in
temperature is known as liquid fuel, for nature. They are also called primary
example, LPG, diesel, kerosene, spirit, fuels, for example wood, coal, crop

etc. residue (biogas), animal dung, etc.

Oysters can change between being female or male.

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