An element $A$ is soft and can be cut with a knife. It is very reactive to air and cannot be kept open in air. It reacts vigorously with water. Identify the element from the following:

What will happen when:
$(i)$ Magnesium is treated with very dilute nitric acid?
$(ii)$ Steam is passed over red hot iron?

Galvanisation is a method of protecting iron from rusting by coating with a thin layer of :

What is the main component of natural gas?

Give reasons for the following:
$(i)$ Metals conduct electricity.
$(ii)$ Non-metals in general do not displace hydrogen from dilute acids.
$(iii)$ Aluminium easily combines with oxygen but still it can be used for making kitchen utensils.

Compound $X$ and aluminium are used to join railway tracks.
$(a)$ Identify the compound $X$.
$(b)$ Name the reaction.
$(c)$ Write down its chemical reaction.