Give reasons :

(a) Platinum, gold and silver are used to make jewellery.

(b) Sodium, potassium and lithium are stored under oil.

(c) Aluminium is highly reactive metal, yet it is used to make utensils for cooking.

(d) Carbonate and sulphides ores are usually converted into oxides during the process of extraction.

(a) Platinum, gold and silver are low reactive metals so they rarely corrode and hence do not lose their shine and lustre. Additionally, they are very malleable and ductile so they can be easily crafted into beautiful jewellery having fine design.

(b) Sodium, potassium and lithium react so vigorously with oxygen that they catch fire if kept in the open. Hence, to protect them and to prevent accidental fires, they are stored under oil.

(c) Aluminium reacts with oxygen present in air to form a thin layer of aluminium oxide on its surface. This oxide layer is very stable and acts as a protective coating by preventing further reaction of aluminium. This combined with aluminium's excellent heat conductivity, easy and cheap availability, malleability and ductility makes it a good choice to make utensils for cooking.

(d) As metals can be easily extracted by the reduction of their oxides rather than from their carbonates and sulphides therefore carbonate and sulphide ores are usually converted into oxides during the process of extraction.