Explain the following in terms of gain or loss of oxygen with two examples each.

(a) Oxidation

(b) Reduction

A shiny brown coloured element 'X' on heating in air becomes black in colour. Name the element 'X' and the black coloured compound formed.

Oil and fat containing food items are flushed with nitrogen. Why?

Explain the following terms with one example each.

(a) Corrosion

(b) Rancidity