The physical properties that are unique to solutions are called colligative properties. Colligative properties of solutions are those that depend upon the number of solute particles, and are independent of the nature of those particles.
Colligative properties of solutions are proportional to the molality of the solution; the more solute that is dissolved in a solution, the greater is the colligative property effect.
The basis of the colligative properties is the increase in entropy that occurs in going from pure solvent (no solute) to having more solute present.
Vapor pressure is a physical property where the pressure of a gas is in equilibrium with its liquid (or solid) phase.