*A single substance decomposes to give two or more substance this type of reaction is called "Chemical decomposition reaction". When decomposition reaction takes place on heating it is also called "Thermal decomposition reaction".
1) Example of chemical decomposition reaction:- calcium carbonate(CaCo₃)⇒ calcium oxide(Cao) + carbon dioxide(Co₂)
2)Example of Thermal decomposition reaction - lead nitrate(Pb(No₃)₂)⇒lead oxide(PbO) +Nitrogen dioxide(No₂) + Oxygen(O₂)
*Displacement reaction :- If one element displaces another element from its compound this type of reaction is called as Displacement reaction.
For example:1) Zinc(Zn)+ hydrochloric acid(HCl)⇒Zinc chloride(Zncl₂)+water(H₂)