Why does a solution containing non-volatile solute have higher boiling point than pure solvent? Why is elevation of boiling point a colligative property?

Boiling point is a temperature at which vapour pressure of a lquid is equal to the atmospheric pressure. For e.g. water boils at 373.15 K.

On adding 1 mole of non-volatile solute the vapour pressure of solvent lowers and the solvent of solution boil at a temperature higher than that of pure solvent.

For e.g. on adding 1 mole of sucrose to 1 kg of water, it boils at 373.52 K.

Elevation of boiling point is a colligative property because it depends only on no. of moles of solute added and not on its nature.