Which of the following is an example of a colligative property?

Freezing point depression is a classic example of a colligative property, which is defined as a property that depends on the number of solute particles in a solution, rather than the identity of those particles. When a non-volatile solute is added to a solvent, the presence of that solute lowers the freezing point of the solvent. This happens because the solute disrupts the formation of the organized lattice structure necessary for the solid phase, requiring a lower temperature to achieve solidification.

Colligative properties also include boiling point elevation, vapor pressure lowering, and osmotic pressure. These properties highlight how the concentration of solute particles affects the physical behavior of a solution, but they do not depend on the chemical identity of the solute, making freezing point depression a clear example of such a property.

Other options listed, such as density, solubility, and acidity, are not classified as colligative properties because they are influenced by specific characteristics of the solute or solvent, rather than just the quantity of solute present.