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Combustion and Flame - Coggle Diagram
Combustion and Flame
Combustion
A chemical process in which a substance reacts with oxygen to give off heat and light is called combustion.
Combustible Substances
Substances which easily catch fire are combustible substances, such as paper, coal, wood.
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Fuel
Any substance, which upon combustion produces a usable amount of energy is known as fuel. For example, fossil fuels, biogas, nuclear energy, etc.
Fuels can be solid, liquid or gas depending on their state.
Fuel Efficiency
Efficiency is that proportion of energy released by a fuel combustion process which is converted into useful work.
The amount of heat energy produced on complete combustion of 1 kg of a fuel is called its calorific value. The calorific value of a fuel is expressed in a unit called kilojoule per kg (kJ/kg).
Ignition Temperature
The lowest temperature at which a combustible substance catches fire when heated in air is called its ignition temperature.
Inflammable Substances
The substances, which have very low ignition temperature and can easily catch fire with a flame are known as inflammable substances. Examples: diesel, LPG, acetone.
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Flame
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Structure of Flame
The outermost zone is the hottest among all zones and is blue in colour and this is due to complete combustion. It is the non-luminous part of the flame.
The middle zone of the candle flame is moderately hot and is yellow in colour, and partial combustion of fuel takes place. It is the bright part of the flame.
The innermost zone of the flame is the least hot and is black in colour. This is due to the presence of unburnt wax vapours.
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