What is an ore of aluminium?

Which substance is used for the chemical reduction of metal oxides like chromium and manganese to obtain the metal?

Which metal does not react with cold or hot water,but reacts with steam to produce $H_2$ gas?

Which of the following metals is a poor conductor of heat and electricity?

List three properties of sodium in which it differs from the general physical properties of most metals.

An alkali metal $A$ gives a compound $B$ (molecular mass $= 40$) on reacting with water. The compound $B$ gives a soluble compound $C$ on treatment with aluminium oxide. Identify $A$,$B$ and $C$ and give the reaction involved.