Burning
1. Burning
Burning, also called combustion, is a chemical reaction in which a substance reacts with oxygen and releases energy in the form of heat, light, and sometimes sound.
Key points
It is a chemical change
New substances are formed
Energy is always released
Usually fast, but can be slow too
2. Conditions Required for Burning
Burning happens only when all three are present:
Fuel – the substance that burns (coal, wood, petrol, LPG)
Oxygen – usually from air
Ignition temperature – minimum temperature needed to start burning
👉 Removing any one of these stops burning.
3. Combustion Reactions (With Equations)
(a) Combustion of Carbon
C+O2→CO2+Heat
(b) Combustion of Hydrogen
2H2+O2→2H2O+Heat
(c) Combustion of Methane (Fuel gas)
CH4+2O2→CO2+2H2O+Heat
4. Products of Combustion
The products depend on oxygen supply.
(a) Complete Combustion
Plenty of oxygen
Produces:
Carbon dioxide (CO₂)
Water (H₂O)
Releases maximum energy
Blue flame
Example:
CH4+2O2→CO2+2H2O
5. Burning of Different Substances
(a) Burning of Metals
Some metals burn in oxygen
Magnesium
2Mg+O2→2MgO2
Forms magnesium oxide (ash)
Iron
Burns slowly (rusting is very slow burning)
Iron wool burns faster
(b) Burning of Non-metals
Carbon, sulfur, phosphorus burn easily
Sulfur
S+O2→SO2
(c) Burning of Fuels
Coal → CO₂ + ash
Petrol/Diesel → CO₂ + H₂O
LPG/CNG → CO₂ + H₂O (cleaner fuels)