Presentation on theme: "Colligative Properties"— Presentation transcript:
1 Colligative Properties Physical properties that are affected by the concentration of solute.
2 Colligative Properties Most common examples are freezing point, boiling point, and vapor pressure.
3 Colligative Properties Freezing point – decreasedBoiling point – increasedVapor pressure - decreased
4 Colligative Properties This makes sense based on kinetic theory. It is harder to freeze with a weird shape in the way. It is harder to boil or have a vapor pressure, because these properties are due to movement of molecules and it is harder to get moving with a weird shape in the way.
5 Colligative Properties For freezing point and boiling point changes, we will use one of two formulas:
6 Colligative Properties MW = (grams of solute)(k)(kg of solvent) (T)MW = molecular weightT = change in boiling or freezing pointK = a constant that varies depending on the solvent.
7 Colligative Properties MW = (grams of solute)(k)(kg of solvent) (T)For water:Kf = (freezing)Kb = (boiling)
8 Colligative Properties This formula can also be arranged as follows:Kb = KfTb TfTb = change in boiling temperatureTf = change in freezing temperature
9 Colligative Properties The other formula that can be used isT = m (k) (n)T = change in freezing or boilingm = molality of the solutionk = freezing or boiling constantn = the number of ions the substance dissociates into when dissolved in water