Explain the following in terms of gain or loss of oxygen with two examples each. (a) Oxidation (b) Reduction

(a) Oxidation is the gain of oxygen. For example,

In equation (i), $\mathrm{H}_{2}$ is oxidized to $\mathrm{H}_{2} \mathrm{O}$ and in equation (ii), $\mathrm{Cu}$ is oxidised to $\mathrm{CuO}$.

(b) Reduction is the loss of oxygen.

For example,

In equation (i), $\mathrm{CO}_{2}$ is reduced to $\mathrm{CO}$ and in equation (ii), $\mathrm{CuO}$ is reduced to $\mathrm{Cu}$.