What happens when
(i) sodium metal is dropped in water?
(ii) sodium metal is heated in free supply of air?
(iii) sodium peroxide dissolves in water?

Explanation

a. `H_(2)` gas is evolved which catches fire due to the exothermicity of the reaction.
`2Na_((s))+2H_(2)O_((l))rarr2NaOH_((aq))+H_2(g)`
b. `Na_(2)O_(2)` along with a small amount of `Na_(2)O` is formed.
`2Na_((s))+O_(2(g))rarrunderset(("Minor"))(Na_(2)O_((s)))`
`Na_(2)O_((s))+1/2O_(2(g))rarrunderset(("Major"))(Na_(2)O_(2)((s)))`
c. `H_(2)O_(2)` is formed as:
`Na_(2)O_(2(s))+2H_(2)O_((l))rarr2NaOH_((aq))+H_(2)O_(2(l))`