Colligative Properties

Colligative properties are those that exist for solutions, and which are generally measured in comparison to a sample of the pure solvent.

Don't worry, I know that doesn't make a lot of sense, but there is no good way to say it without a specific example. So, let's get to it.

There are 4 colligative properties that you should know about.

• They are: Decreasing Vapor Pressure – the vapor pressure of the solvent decreases when a solute is added. (In simpler English – the vapor pressure of salt-water is less than that of pure water.) 
• Boiling Point Elevation – the boiling point of a solution is higher than that of the pure solvent. (In simpler English – the boiling point of salt-water is higher than that of pure water.) 
• Freezing Point Depression – the freezing point of a solution is lower than that of the pure solvent. (In simpler English – the freezing point of salt-water is lower than that of pure water.) 
• Osmotic Pressure – The tendency of a solvent to move through a semi-permeable membrane is decreased when a solute is added. (In simple English – water will go through your skin faster than salt water will). This will require the most explanation, but it is worth understanding since this describes more real-world experiences than the others do.