What is a colligative property?

A colligative property is defined as a property that depends on the number of solute particles in a solution rather than the type or identity of those particles. This means that when a solute is added to a solvent, the effect on properties such as boiling point elevation, freezing point depression, osmotic pressure, and vapor pressure lowering relates directly to how many solute particles are present, not what those particles consist of chemically.

For instance, when sodium chloride (table salt) dissolves in water, it dissociates into two ions (Na+ and Cl-), effectively increasing the number of solute particles in the solution. The changes observed in the boiling point or freezing point arise from this increase in particle concentration.

In contrast, properties that depend on the type of solute, are independent of solute concentration, or only apply to specific states of matter do not fit the definition of colligative properties. Understanding this concept is crucial in various applications, including predicting how solutions behave when solutes are added and calculating properties in chemistry and biochemistry contexts.