Freezing point depression is colligative because it is related to the number of solute particles, making it a property that depends on the concentration rather than the specific identity of the solute.
Freezing point depression is a colligative property because it depends on the number of solute particles present in a solution, rather than the identity of the solute particles. Colligative properties are properties of a solution that depend only on the quantity of solute particles, not on the nature of the solute particles.
The freezing point of a solvent is lowered when a non-volatile solute is added to it. This occurs because the solute particles disrupt the regular crystal lattice structure that forms in the pure solvent during freezing. The more solute particles present in the solution, the greater the disruption, and the lower the freezing point becomes.
The colligative nature of freezing point depression is explained by the fact that the extent of this depression is proportional to the concentration of solute particles, regardless of their chemical nature. This relationship holds according to the Van't Hoff factor, which takes into account the number of particles a solute dissociates into (if it's an ionic compound) or the number of molecules it forms (if it's a molecular compound).
The probable question may be "What is the reason why freezing point depression is a colligative property?"