The sulphide ores are converted into oxides by heating them strongly in the presence of excess air. This process is called
Roasting
The metals in the middle of the activity series such as Iron, Zinc, Lead, Copper, etc., are moderately reactive. These are usually present as sulphides or carbonates in nature. It is easier to obtain a metal from its oxide, as compared to its sulphides and carbonates. Therefore, prior to reduction, the metal sulphides and carbonates must be converted into metal oxides. This is done by treating the ore or ore concentrate with very hot air. This process is known as roasting.