$(a)$ List two differences between calcination and roasting in tabular form.
$(b)$ Which method will you use to reduce the following? Explain by giving a suitable example.
$(i)$ Oxides of less reactive metals.
$(ii)$ Oxides of moderately reactive metals.
$(iii)$ Oxides of highly reactive metals.

(N/A)

Roasting	Calcination
Heating in the presence of excess air. Done for sulphide ores.	Heating in a limited supply of air. Done for carbonate ores.

$(b)$ $(i)$ Self-reduction: Less reactive metals like mercury $(Hg)$ or copper $(Cu)$ can be reduced by heating alone.
$2HgO \xrightarrow{\text{heat}} 2Hg + O_2$
$2Cu_2O + Cu_2S \xrightarrow{\text{heat}} 6Cu + SO_2$
$(ii)$ Reduction using carbon or displacement: Moderately reactive metals are reduced by heating with carbon or using highly reactive metals like aluminum $(Al)$ in thermite reactions.
$ZnO + C \rightarrow Zn + CO$
$Fe_2O_3 + 2Al \rightarrow 2Fe + Al_2O_3 + \text{Heat}$
$(iii)$ Electrolytic reduction: Highly reactive metals (e.g.,$Na, Mg, Ca$) are extracted by the electrolysis of their molten chlorides because they have a high affinity for oxygen.