1. Changes in State
Phase Changes

2. C11-1-05 KINETIC MOLECULAR THEORY
OUTCOME QUESTION(S):
C KINETIC MOLECULAR THEORY
Describe the properties of gases, liquids, solids and plasma.
Include: compressibility, diffusion
Use the Kinetic Molecular Theory to explain properties of solids, liquids and gases.
Include: intermolecular forces, elastic collisions, kinetic energy,
temperature and particle motion
Understand the various phase changes in terms of KMT.
Include: sublimation, deposition, evaporation, condensation
Vocabulary & Concepts 
Characteristic Property Vapour

3. Phase changes involve a change in energy:
Can be endothermic ----or---- exothermic
Energy is absorbed Energy is released
Why is a change in energy necessary at all in a phase change?

4. IMFs (attraction) must be broken in order for a substance to change states/phases.
less dense
less dense
Think of particles like little magnets – they attract – to pull them apart, it takes energy… H O δ- δ+ + Na - Cl
ions
dipoles

5. Energy must be absorbed to melt/boil (endothermic)
Heating Curve:
A graph of the temperature of a substance plotted against the amount of energy absorbed.
Energy must be absorbed to melt/boil (endothermic)
Temperature will plateau even though energy is still being added
At this point, all added energy is used to break attraction (IMFs) NOT to increase temperature (KE)

6. Melting or Fusion (s) (l) Endothermic process
Absorbed energy is utilized to reduce IMFs
Particles move more freely - liquid
Called
Heat of Fusion
energy absorbed break IMFs
Melting point is a characteristic property – unique, and can be used to identify substances
energy added mp
all particles “freed”

7. The greater the attraction between the particles, the more energy needed to overcome the IMF.
No charge
Small charge
Big charge
Non-polar
Polar
Ionic
weakest IMF
strongest IMF C H H O δ- δ+ + Na - Cl
ions C H
dipoles

8. (larger molecule – more attraction)
Organize these compounds from lowest to highest melting point:
First: identify the type of compound / IMFs present.
CH MgCl C4H SO2
Non-polar
Ionic/ions
Non-polar
Polar/dipoles
Secord: place in order of increasing IMF.
(more attraction – more energy needed to phase change)
increasing melting point
CH C4H SO MgCl2
Non-polar
Non-polar
Polar/dipoles
Ionic/ions
-182oC oC oC oC
Note: generally as mass increases, melting/boiling point also increases.
(larger molecule – more attraction)

9. Boiling point is also a characteristic property
Vaporization
(l) (g)
Endothermic process
Energy is utilized to further reduce IMFs
Particles move unrestricted - gas
Heat of Vaporization
energy absorbed
energy added
Boiling point is also a characteristic property bp
all particles “free”
Vapour: a liquid that has phase changed to “gas”
(water vapour)
Gas: substance found normally in this state
(propane gas)

10. Remember: high energy particles go first
There are two types of vaporization:
1. Boiling (forced)
Liquid particles at the bottom are given enough energy to overcome IMFs - vapour created.
2. Evaporation (natural)
Liquid particles on the surface that have enough energy to overcome IMFs - vapour released.
Particles on the surface have fewer IMFs to contend with…
Remember: high energy particles go first

11. Think of magnets attracting together…
Cooling Curve:
Particles lose energy and are pulled together by IMFs
Energy released as particles condense/freeze into more restrictive phases (exothermic)
Temperature will still plateau during phase change
liquid
gas
solid
Energy Removed F E D C B A
phase change
(condensation)
(freezing)
Think of magnets attracting together…
SNAP! – energy released

12. Condensation or Liquefaction
(g) (l)
Particles slow as kinetic energy is lost
Energy released as IMF take hold and restrict movement
Exothermic process
liquid
gas
solid
Energy Removed F E D C B A
phase change
(condensation)
(freezing)
Condensation point occurs at the same temperature as Boiling point… bp
all particles “captured”
Kinetic energy lost
energy released

13. Freezing or Solidification
(l) (s)
Particles continue to slow as more energy is lost
IMF strengthen, restrict to crystalline/amorphous structure
Exothermic process
liquid
gas
solid
Energy Removed F E D C B A
phase change
(condensation)
(freezing)
Freezing point occurs at the same temperature as Melting point… mp
all particles in solid structure
energy lost
nrg released

14. Sublimation: Deposition:
The direct phase transition of a substance from solid to vapour without passing through the liquid state.
Endothermic
These are rare phase changes that occur with specific pressures as well as temperatures…
Deposition:
The direct phase transition of a substance from vapour to solid without passing through the liquid state.
Exothermic

15. Below are two different heating curves:
a. What is the freezing point of these two substances?
b. Predict which substance has the strongest IMF?
a. 17oC and 0oC
b. First substance
Higher melting point of first substance indicates more energy needed to contend with (likely) stronger IMF

16. Water is Special: NP P P
The increase in IMF strength accounts for increases in melting/boiling – water has unusually strong IMF

17. regular atmospheric pressure
Phase diagram:
Summarizes the effect of temperature and pressure on a substance in a closed container.
Each state is favoured by certain conditions:
Low temperatures with high pressures favour formation of solid
High temperatures with low pressure favour formation of gas
Triple Point: Temperature/pressure where all three states can exist.
regular atmospheric pressure

18. Increased kinetic energy (temperature)
Increased particle motion
Reduced IMF
Decreased kinetic energy (temperature)
Decreased particle motion
Increased IMF

19. C11-1-05 KINETIC MOLECULAR THEORY
CAN YOU / HAVE YOU?
C KINETIC MOLECULAR THEORY
Describe the properties of gases, liquids, solids and plasma.
Include: compressibility, diffusion
Use the Kinetic Molecular Theory to explain properties of solids, liquids and gases.
Include: intermolecular forces, elastic collisions, kinetic energy,
temperature and particle motion
Understand the various phase changes in terms of KMT.
Include: sublimation, deposition, evaporation, condensation
Vocabulary & Concepts 
Characteristic Property Vapour