Colligative properties are properties of a solution that depend only on the number of solute particles (molecules or ions) in a given amount of solvent, and not on their chemical nature.
Examples of Colligative Properties:
- Relative Lowering of Vapor Pressure
- Adding a non-volatile solute (like sugar or salt) to a solvent lowers its vapor pressure.
- Example: Saltwater has a lower vapor pressure than pure water.
- Elevation of Boiling Point
- The boiling point of a solution is higher than that of the pure solvent.
- Example: Salt added to water makes it boil at a temperature above 100 °C.
- Depression of Freezing Point
- The freezing point of a solution is lower than that of the pure solvent.
- Example: Salt is spread on icy roads in winter because it lowers the freezing point of water, melting the ice.
- Osmotic Pressure
- The pressure required to stop osmosis through a semipermeable membrane.
- Example: Reverse osmosis used in water purifiers; plant roots absorbing water.
In short: The four colligative properties are lowering of vapor pressure, elevation of boiling point, depression of freezing point, and osmotic pressure — all depending only on solute particle concentration.