By definition, one of the properties of a solution is a colligative property if it depends only on the ratio of the number of particles of solute and solvent in the solution, not the identity of the solute. The examples of colligative properties are:
1) Relative vapour pressure reduction- The vapour pressure of a solution is always lower than the vapour pressure of the pure solvent; the ratio of solution to pure solvent vapour pressure is approximately equal to the mole fraction of solvent in the solution.
2) Boiling point elevation- The phenomenon that occurs when the boiling point of a liquid (a solvent) is increased when another compound is added, such that the solution has a higher boiling point than the pure solvent. Boiling point elevation occurs whenever a non-volatile solute is added to a pure solvent.
3) Freezing point depression- It is the phenomenon that occurs when the freezing point of a liquid(a solvent) is lowered by adding another compound to it, such that the solution has a lower freezing point than the pure solvent.
4) Osmotic pressure- It is the pressure produced due to the movement of one component of a solution through a membrane to dilute the solution.This pressure depends on the ratio of the number of solute particles to the volume of the solution.
It, however,depends upon the actual no. of species in solutions and is modified when a solute undergoes dissociation or association in solutions.