Chapter Review:
- The chemical process in which a substance reacts with oxygen and gives heat is called combustion.
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The substance that undergoes combustion is said to be combustible. It is also called a fuel.
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The lowest temperature at which a substance catches fire is called its ignition temperature.
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The amount of heat energy produced on complete combustion of 1 kg of a fuel is called its calorific value. Its unit is kilojoules per kg (kj/kg)
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The substances which have very low ignition temperature and can
easily catch fire with a flame are called inflammable substances. Examples of inflammable substances are petrol, alcohol, Liquified Petroleum Gas (LPG), etc. -
There are three different zones of a flame - dark zone, luminous zone and non-luminous zone.
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Phosphorus which burns in air at room temperature.
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The type of combustion in which a material suddenly bursts into flames, without the application of any apparent cause is called spontaneous combustion.
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A large amount of gas formed in the reaction is liberated. Such a reaction is called explosion.
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The sources of heat energy for domestic and industrial purposes are mainly wood, charcoal, petrol, kerosene, etc. These substances are
called fuels. -
Combustion of most fuels releases carbon dioxide in the environment.
Increased concentration of carbon dioxide in the air is believed to cause global warming. -
Oxides of sulphur and nitrogen dissolve in rain water and form acids. Such rain is called acid rain.
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Incomplete combustion of a fuel gives poisonous carbon monoxide gas.
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An ideal fuel is cheap, readily available, readily combustible and easy to transport. It has high calorific value. It does not produce gases or
residues pollute the environment.
