Define calcination and roasting.

Explanation

Calcination : Calcination is a process of heating the ore strongly either in a limited supply of air or in tlie absence of air.
Example :
`underset(("Zincoxide"))(ZnO(s)) overset("Calcination")to Zn + 1/2 O_2(g)`
Roasting : Roasting is a process of heating the ore strongly in the presence of excess of air at a temperature below the melting point of the metal.
Example :
`underset(("Zinc Slphide"))(2ZnS + 3O_2) to underset(("Zinc Oxide"))(2ZnO) + 2SO_2`