All cases of phase change (melting vapourization, etc.) are physical changes because they are gencrally reversible.
- Dissolution of salts in water is reversible and so it is a physical change
- Separation of the components of a mixture by distillation: does not produce new kinds of matter; is a reversible process; is not accompanied by great heat change. And so, it is a physical change
- In rusting of iron: a new kind of matter is formed; the process is irreversible; and hence, it is a chemical change.