Chemistry Lecture 5: Heat Capacity, Phase Change, and Colligative Properties

A measure of the energy change needed to change the temperature of a substance.

C = q/ ΔT

q = CΔT

Heat capacity per unit mass

q = mcΔT

Constant pressure calorimeter, measures energy change at atmospheric pressure; measures energy change at atmospheric pressure

Measures energy change at constant volume; tells the internal energy change in a reaction

Enthalpy change associated with melting

Enthalpy change associated with boiling

Point where a substance can exist in equilibrium as a solid, liquid, and gas

Temperature at which a substance cannot be liquefied regardless of the pressure applied

Pressure required to produce liquefaction while the substance is at the critical temperature

Critical temperature and critical pressure together

Depend solely on the number of particles.

Four colligative properties

1. Vapor pressure
2. Boiling point
3. Freezing point
4. Osmotic pressure

ΔT = (Kb)mi

m= molality
i = van't Hoff factor; number of particles into which a single solute particle will dissociate when added to solution

ΔT = (Kf)mi

The tendency of a fluid, usually water, to pass through a semipermeable membrane into a solution where the solvent concentration is higher, thus equalizing the concentrations of materials on either side of the membrane.

Π = iMRT

Πb = ρghb - ρgha

M = Molarity

mol = weight of sample (g) / molar weight (g/mol)