What happens to the freezing point of a pure solvent when a solute is added?

When a solute is added to a pure solvent, the freezing point of the solution is lowered compared to that of the pure solvent. This phenomenon, known as freezing point depression, occurs because the presence of solute particles interferes with the formation of the organized structure of ice.

In a pure solvent, molecules can easily arrange themselves into a solid crystalline structure when freezing occurs. However, when a solute dissolves in the solvent, the solute particles disrupt this arrangement. As a result, a lower temperature is required to achieve the necessary conditions for freezing — hence, the freezing point of the solution becomes lower than that of the pure solvent.

This concept is a colligative property, which means that it depends on the number of solute particles in the solution rather than the identity of the solute itself. Therefore, the correct understanding of how adding a solute influences the freezing point highlights the impact of solute particles on physical properties of solutions.