(a) Sodium reacts with oxygen at room temperature to form sodium oxide (Na20). This is a basic oxide and dissolves in water to form sodium hydroxide, an alkali.
(b) Magnesium burns in air with a dazzling white flame once heated to a temperature called its ignition temperature. It does not react with air at room temperature.
(c) Copper and iron metals are less reactive and react with oxygen only on prolonged heating.
(ii) Reaction with water:
More reactive metals react with water at room temperature but less reactive metals react on heating with water or steam. Hydrogen is formed in all these cases.
Sodium and potassium react with water at room temperature very briskly and forms sodium hydroxide and hydrogen gas is evolved.
2Na + 2H20 ——- > 2NaOH + H2
Magnesium and calcium react slowly with cold water but react rapidly with boiling water but metals like aluminium, iron and zinc do not react with water, they react with steam.