COMBUSTION & FLAME ncert_CLASS8

COMBUSTION : 

• a chemical process in which substance reacts with oxygen to give off heat is called as combustion 

• The substance that undergoes combustion called as fuel 

• The lowest Temperature at which the substances catches fire is called its IGNITION TEMPERATURE 

• Substances which have very low Ignition Temperature and easily catch fire with a flame are called Inflammable substances 

• Eg : Petrol , alcohol , LPG 

CALORIFIC VALUE : 

• 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 kilo joule per kg (KJ/Kg) 

CAUSES OF ACID RAIN : 

• Due to heavy pollution when oxides of sulfur and nitrogen dissolve in rain water and form acids such rain is called as Acid Rain