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Fuels and their Composition

Short Notes on Important Fuels and their Composition


  • The substance, which produce heat and light on combustion are called fuels.
  • A strong foul smelling substance, called ethyl mercaptan is added to LPG to detect its leakage as LPG is an odourless gas.

 Some Important Fuels and their Compositions

Important Fuels and their Composition

Physical and Chemical Changes

  • Physical changes are the change, which only affect the physical properties like colour, hardness, density, melting point etc. of matter, but do not affect the composition and chemical properties of matter.
  • A physical change is temporary, while a chemical change is permanent.
  • Crystallisation, sublimation, 'boiling, melting, vaporisation, cutting of trees, dissolving sugar or salt in water etc. are physical changes.
  • Chemical changes affect the composition as well as chemical properties of matter and result in the formation of a new substance.
  • Burning of fuel, burning of candle and paper, electrolysis of water, photo­synthesis, ripening of fruits etc, are examples of chemical changes


Coal is obtained by carbonization of vegetable matter and is available in different varieties:
  • Peat- 60% C
  • Lignite or Brown Coal – 70% C
  • Bituminous – 60 to 80 % C
  • Anthracite Coal – 90% C
  • Fame

Flame contains three parts

  1. Innermost Part- which is black due to the presence of unburned carbon particles- has lowest temperature.
  1. Middle part – is yellow due to incomplete combustion of fuel.
  1. Outermost part- which is blue due to complete combustion of fuel is the hottest and used by goldsmith to heat the gold.

Fire Extinguishers

  • Water extinguishes fire because as it evaporates, the vapours surround the burning substance, cutting off the oxygen supply, thus inhibiting burning process.
  • In case of electrical or oil (petrol) fires, water cannot be used as extinguisher. This is because water is a conductor of electricity and heavier than oil. Thus, oil floats over it and continues to burn.
  • Carbon dioxide, which is generated by the reaction of baking soda with acid, is used extinguish electrical or oil fires. Quality of petrol is measured in terms of octane number and that of diesel in terms of cetane number.

Safety Matches

In safety matches, the stick consists of mixture of antimony trisulphide and potassium chlorate at its one end. The box side contains a mixture of powdered glass and phosphorus.