1. Changes of State Objectives:
1. Relate changes in state to changes in energy.
2. Compare the different states of matter in terms of potential and kinetic energy
3. Describe the major events that occur along a heating curve.
4. Interpret a phase diagram.
Key Terms:
Vaporization, condensation, evaporation, equilibrium, vapor pressure, boiling point, heat of vaporization, freezing point, heat of fusion, sublimation, deposition, heating curve, phase diagram

2. Energy and Phase Changes
According to the kinetic-molecular theory, a substances phase is determined by the balance of its kinetic and intermolecular forces. What this means is that you can convert matter from one phase to another by simply adding or deleting kinetic energy (heat).

3. Changes in State
liquid to gas - vaporization, by process of evaporation
solid to gas - sublimation
liquid to solid - freezing
solid to liquid - melting
gas to liquid - condensation
gas to solid – deposition
triple point – where all
phases are in equilibrium

4. Heating Curve
The heating curve is a representation of the phases of a substance compared to the temperature and internal energy of a substance. The blue lines represent the different phases of a substance while the red lines represent the heats of fusion and vaporization.
endothermic reactions move from left to right as the products increase in kinetic energy and become less organized

5. Heat Associated with Phase Changes
Heat of fusion (DHfus) - the amount of heat absorbed as 1 mole of a substance melts
occurs between B & C
endothermic
occurs at constant temperature
H2O(s) g H2O(l) DHfus = 6.01kJ/mol
Heat of solidification (DHsolid) - the amount of heat released as 1 mole of a substance solidifies
exothermic
H2O(l) g H2O(s) DHsolid = -6.01kJ/mol
Heat of vaporization (DHvap) - the amount of heat absorbed as 1 mole of a substance solidifies
occurs between D & E
H2O(l) g H2O(g) DHvap = 40.7kJ/mol
Heat of condensation (DHcond) - the amount of heat released as 1 mole of a substance solidifies
H2O(g) g H2O(l) DHcond = -40.7kJ/mol

6. Heat of Solution
Heat of solution (DHsol) - the amount of heat absorbed or released as 1 mole of a substance dissolves in 1L of solution
exothermic or endothermic
NaOH(s) g Na+(aq) + OH-(aq) DHsol = kJ/mol
NH4NO3(s) g NH4+(aq) + NO3-(aq) DHsol = 25.7kJ/mol