1. Colligative Properties
How solutes affect the properties of solutions.

2. What determines colligative properties?
Colligative Properties depend on the concentration of the solute particles.
They DO NOT depend on what the solute particles are.

3. Four Major Effects of Solute
Effect on vapor pressure
vapor pressure of the solvent in a solution is decreased by the solute. the more solute is present, the more the vapor pressure of the water is lowered.

5. Why does vapor pressure of the solvent decrease?

6. Effect on Freezing Point
The addition of a solute to a solvent causes the freezing point of the solution to decrease.
How do you
get from this…

7. …to this?

8. Add an ionic compound!

9. Car Radiators & Antifreeze

10. Did you know?
Some animals are able to survive freezing temperatures by producing natural antifreezes
substances that lower the freezing point of a liquid.
many freeze-tolerant insects, the antifreezes are alcohols and sugars.

11. Effect of solute on Boiling Point
The addition of a solute to a solvent raises the boiling point of the solution.

12. Adding a solute increases the boiling point

14. Normal Boiling Point of Water

15. Water can boil at different temperatures
Since boiling pt. is the temp. where the vapor pressure equals the pressure above the liquid, changing the pressure affects boiling pt.
What is the boiling pt. for pure water where the pressure above the water is:
40 kPa
80 kPa
150 kPa

16. Osmosis
Osmosis
the diffusion of a solvent through a semipermeable membrane from an area of higher solvent concentration to an area of lower solvent concentration.
Osmotic pressure
is the amount of additional pressure caused by water molecules that moved into the concentrated solution.

17. Osmosis