Identify the substances that are oxidised and that are reduced in the following equation.
(i) 4Na(s) + O2(g) → 2Na2O(s)
(ii) CuO(s) + H2(g) → Cu(s) + H2O(l)

With the addition of oxygen (O₂) in the first equation, the sodium (Na) becomes oxidised, and the reduction of copper (Cu) in the second equation results from the addition of hydrogen (H₂).