1. Phases of Matter, Bonding and Intermolecular Forces

2. While a phase change takes place the temperature remains the same.
The energy added is being used to overcome the intermolecular forces between the molecules, and pull the molecules away from each other.
The more energy that is used to pull the particles apart, the farther apart the molecules are, and this energy is stored as potential energy (PE).

3. So, during a phase change the energy being added is used to change the
The farther apart the particles are, the greater their potential energy, the closer they are the lower their potential energy.
So, during a phase change the energy being added is used to change the
Potential Energy PE of the molecules.
Because of the Law of Conservation of Energy – the kinetic energy (KE) remains constant
and since KE is proportional to temperature,
the temperature remains constant.

4. See Diagram on overhead 

5. EXOTHERMIC Reactions – process in which heat energy is released.
ENDOTHERMIC Reactions – process in which heat energy must be added.

6. Do Freezing and Boiling Point Graph WS

7. 334 J/g HEAT OF FUSION Fusion = Melting
– the energy or amount of heat required to change a unit
mass of a solid to a liquid at constant temperature.
Fusion = Melting
Heat of Fusion = Hf Hf for water =
(see Table B)
Note Conservation of Energy: when 1 gram of water is frozen into ice, the same amount of
heat is given off as needs to be added to melt 1 gram of ice to water.
334 J/g

8. 2260 J/g HEAT OF VAPORIZATION
- the energy or amount of heat required to vaporize
a unit mass of a liquid to a gas at constant temperature.
Heat of Vaporization = Hv Hv for water = (see Table B)
2260 J/g

9. q = m C ΔT q = m Hf q = m Hv CALCULATING HEAT - Table T
q = m C ΔT
q = m Hf
q = m Hv
q = heat (Joules)

10. CALCULATING HEAT - Table T q = m C ΔT q = m Hf q = m Hv
q = m C ΔT
q = m Hf
q = m Hv
 q = heat (Joules)
m =
ΔT =
mass (g)
Tf -Ti (Celsius or Kelvin)

11. C = specific heat capacity Hf = heat of fusion (melting)
 Note:
The following are reference values that will be given or
if substance is water look up value on see table B.
C = specific heat capacity
Hf = heat of fusion (melting)
Hv = heat of vaporization

12. PHASE DIAGRAM