Give reasons
(a) Platinum, gold and silver are used to make jewellery.
(b) Sodium, potassium and lithium are stored under oil.
(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.

Explanation

(a) Platinum gold and silver are used to make jewellary because of their bright shiny surface and high resistance to corrosion. Also they have high malleability and ductility.
(b) Sodium, potassium and lithium are stored under oil to prevent their reaction with oxygen, moisture and carbon dioxide of air so as to protect them as they are highly reactive metals.
(c ) Aluminium metal forms a thin layer of aluminium oxide all over its surface under the action of moist air. This layer prevents the metal underneath from further corrosion. It is cheap, easily avaialable , malleable and ductile. Therefore, it is used to make utensils for cooking.