Colligative properties

Science

Definition

Colligative properties are properties of solutions that depend on the number of dissolved solute particles, not the identity of the solute. The four main colligative properties are boiling point elevation, freezing point depression, vapor pressure lowering, and osmotic pressure.

Examples

  • Adding salt to roads in winter lowers the freezing point of water, melting ice
  • Antifreeze (ethylene glycol) raises the boiling point and lowers the freezing point of radiator fluid
  • Saltwater boils at a slightly higher temperature than pure water
Key Fact

ΔTb = iKbm and ΔTf = iKfm, where i is the van 't Hoff factor, K is the constant, and m is molality.

Related Terms

Concentration Solubility Water properties Phases of matter

Study This Concept

Practice colligative properties with free review games in these units:

Chemistry Unit 7: Solutions and Mixtures