Explain roasting, calcinations and smelting.

These are the methods which are used to convert ore into metal oxides.

i) Roasting: When sulphide containing ore is heated for a long time in presence of excess of air to form metal oxide, this method of converting sulphide containing ore into metal oxide in presence of excess of air is called roasting.

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ii) Calcination: When carbonate containing ore is heated for a long time in absence of air it is converted into metal oxide. This method of converting carbonate containing ore into metal oxide is called calcination.

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iii) Smelting: If the ore is in melted form then it is called smelting.