The vapor pressure of a solution containing a non-volatile solute is lower than that of the pure solvent. Consequently, the boiling point of a solution is higher. The freezing point of a solvent is also affected by the solute; the freezing point of a solution is lower than that of the pure solvent. The freezing point of a solution, Tf, is Tf = T°f – ∆Tf Where T°f is the freezing point of the pure solvent and ∆Tf is the freezing point depression. Freezing point depression, like boiling point elevation, is termed a colligative property. Such properties depend only on the concentration of the solute particles in the solution, and not on their nature. For dilute solutions, ∆Tf = mKf = T°f – Tf (1) Where m is the molality of the solution and Kf is the molal freezing point depression constant, a property of the solvent.