Colligative properties are a group of physical properties that depend on the concentration of solute particles in a solvent, regardless of the nature of the solute. These properties are unique to solutions and can be used to determine the concentration or molecular weight of a solute.

The term "colligative" comes from the Latin word "colligare," meaning "to bind together." Colligative properties arise from the collective behavior of solute particles in a solution, rather than the specific chemical identity of the solute.

The four primary colligative properties are:

• Vapor Pressure Lowering: When a non-volatile solute is dissolved in a solvent, the vapor pressure of the solvent decreases. This decrease in vapor pressure is directly proportional to the concentration of solute particles in the solution.

• Boiling Point Elevation: The boiling point of a solvent increases when a non-volatile solute is dissolved in it. The extent of boiling point elevation depends on the concentration of solute particles in the solution.

• Freezing Point Depression: The presence of a solute in a solvent lowers its freezing point. The more solute particles in the solution, the greater the freezing point depression.

• Osmotic Pressure: Osmotic pressure is the pressure required to prevent the flow of solvent molecules across a semipermeable membrane, caused by the presence of solute particles. It is directly proportional to the concentration of solute particles in the solution.

These colligative properties are based on the idea that the presence of solute particles disrupts the normal behavior of the solvent molecules, affecting their physical properties. The magnitude of these effects depends solely on the concentration of solute particles, not on the nature of the solute itself.