Chemical decomposition : A chemical reaction in which a single substance splits into two or more substances is called chemical decomposition.
For decomposition reaction where energy is supplied in the form of :
a) Heat : On heating calcium carbonate decomposes into calcium oxide and carbondioxide.
b) Light: Silver bromide decomposes to silver and bromine in sunlight.
c) Electricity : On passing the electricity, water dissociates to hydrogen and oxygen.