Salt raises boiling point but lowers melting point


Adding salt to water raises its boiling point but lowers its melting point.

The sodium chloride ions dissociate in the water and form bonds with the water molecules. These bonds are stronger than the bonds between the water molecules themselves, so more energy is required by the water to break free into water vapour.

Similarly, more energy is required to “exclude” the sodium and chloride ions when water is freezing, so the freezing point / melting point is lowered.