1. What do all of these have in common?
Slipping and Sliding Car
Ice cream and Cake
Overheating
Frogs Hibernating

2. Colligative Properties
property of a solution that depends only upon the number of solute particles, not upon their identities

3. Examples of Colligative Properties
boiling-point elevation: when a solute is dissolved in a solvent, it raises the temperature at which the solvent boils
freezing-point depression: when a solute is added to a solvent, it lowers the temperature at which the solvent freezes

4. The more solute particles, the greater the effect on these properties
When solutes are dissolved in solutions, they change the boiling point, freezing point, etc. of the solvent…
The more solute particles, the greater the effect on these properties
How can you get a lot of particles dissolved?
Increase molarity /molality
Choose your solute carefully…

5. If you had a 1.0 M solution of each of these, which would have the lowest freezing point?
NaCl 
MgBr2 
Al(NO3)3 
C6H12O6 
Na+ + Cl-
2 particles
Mg2+ + 2Br-
3 particles
Al3+ + 3NO3-
4 particles
C6H12O6
1 particle
Al(NO3)3 would lower the freezing point the most!

6. Real World Application
Salting roads
Making ice cream
Antifreeze
Amphibians and Insects

7. Freezing Point Depression
ΔTf = iKfm
ΔTf = freezing point depression (°C)
i = van’t Hoff constant (number of particles when dissolved)
Kf = freezing point depression constant
m = molality = moles of solute/kg of solvent

8. Boiling Point Elevation
ΔTb= iKbm
ΔTb= boiling point elevation (°C)
i = van’t Hoff constant (number of particles when dissolved)
Kb = boiling point elevation constant
m = molality = moles of solute/kg of solvent

9. Example: If 1800 g of ethylene glycol (C2H6O2) is added to 1900 g of water, at what temperature will the water boil?
First: Determine the molality of the solution. molality = moles of solute/kg of solvent = 29.03… moles/1.9 kg =15… m

10. Second: Determine how many particles the solute will divide into when dissolved in water.
Ethylene glycol (C2H6O2) is a molecular compound, so it will not dissociate like ionic compounds. So…1 molecule of C2H6O2 will only produce 1 molecule of C2H6O2 when dissolved in water. Thus, i = 1.

11. Third: Enter values into the equation ΔTb = iKbm
ΔTb = iKbm i = 1 Kb = °C/m m = 15…m ΔTb= (1)(0.512)(15.28…) = 7.8 °C = 107.8°C