1. I. Kinetic Molecular Theory KMT

2. Assumptions of KMT All matter is composed of tiny particles
These particles are in constant, random motion.
Some particles are moving fast, some are moving slowly.
Temperature is a measure of the average Kinetic Energy and is proportional to the average speed of the molecules.

3. KMT Model http://preparatorychemistry.com/Bishop_KMT_frames.htm
Click on the link above to see how particles of matter behave according to the KMT.

4. II. Intermolecular Forces
Liquids & Solids
II. Intermolecular Forces

5. Definition of IMF Attractive forces between molecules.
Much weaker than chemical bonds within molecules.
a.k.a. van der Waals forces

6. Types of IMF
London Dispersion Forces
View animation online.

7. Types of IMF
Dipole-Dipole Forces + -
View animation online.

8. Types of IMF
Hydrogen Bonding

9. Types of IMF

10. III. Physical Properties
Liquids & Solids
III. Physical Properties

11. Liquids vs. Solids IMF Strength Fluid Density Compressible Diffusion
Stronger than in gases Y
high N
slower than in gases
SOLIDS
Very strong N
high
extremely slow

12. Liquid Properties Surface Tension
attractive force between particles in a liquid that minimizes surface area

13. Liquid Properties Capillary Action
attractive force between the surface of a liquid and the surface of a solid
water
mercury

14. Types of Solids Crystalline - repeating geometric pattern
covalent network
metallic
ionic
covalent molecular
Amorphous - no geometric pattern
decreasing
m.p.

15. Types of Solids
Ionic
(NaCl)
Metallic

16. Types of Solids Covalent Molecular Covalent Network Amorphous (H2O)
(SiO2 - quartz)
Amorphous
(SiO2 - glass)

17. Liquids & Solids
IV. Changes of State

18. Phase Changes Most substances can exist in 3 states: Solid Liquid Gas
Depends on temperature and pressure

19. Phase Changes

20. Phase Changes Each state is referred to as a “Phase”
Ice water is a heterogeneous mixture of 2 phases
When energy is added or removed, one phase can change into another

21. Phase Changes Requiring Energy
Melting
Vaporization
Sublimation

22. Melting
Amount of energy needed to melt a substance depends on forces keeping particles together.
Melting water requires a high amount of energy because of hydrogen bonding
Adding energy allows molecules to move faster, breaking the hydrogen bonds
Melting point - Temperature at which the forces holding crystal lattice together are broken and substance becomes liquid

23. Phase Changes IMF m.p. Melting Point equal to freezing point
Which has a higher m.p.?
polar or nonpolar?
covalent or ionic?
polar
ionic

24. Vaporization
In liquid water, some particles will have more kinetic energy than others.
When the particles have enough energy to overcome the forces of attraction they will escape the liquid as a gas.
Vapor - A substance that is liquid at room temperature and becomes gas.
Vaporization - the process of changing a liquid to a gas

25. Vaporization
Evaporation - Vaporization that occurs at the surface of a liquid, molecules at the surface gain enough energy to overcome IMF
Evaporation is gradual
Even at cold temperatures, some molecules have enough energy to break the attractions and become gas.
Evaporation is how your body cools itself
Water in sweat absorbs heat from your body
Water evaporates leaving less heat in your body and a lower ‘average kinetic energy’ (lower temperature)

26. Phase Changes temp v.p. IMF v.p. Vapor Pressure
pressure of vapor above a liquid at equilibrium
v.p.
depends on temp & IMF
temp
temp
v.p.
IMF
v.p.

27. Phase Changes Patm b.p. IMF b.p. Boiling Point
Temperature at which the vapor pressure of a liquid equals the external atmospheric pressure
depends on Patm & IMF
Normal B.P. - b.p. at 1 atm
Patm
b.p.
IMF
b.p.

28. Sublimation
Sublimation - when a substance goes from solid directly to gas without becoming a liquid
Solid iodine
Frozen carbon dioxide (dry ice)
Moth balls (p-dichlorobenzene)
Solid air fresheners
Ice cubes left in a freezer for a long time

29. Phase Changes the Release Energy
Condensation
Deposition
Freezing

30. Condensation Condensation – process of changing from gas to liquid
When molecule s lose energy,
Velocity of the molecules is reduced
Intermolecular forces take over
Hydrogen bonds form, energy is released (heat comes out)
There are different causes for condensation, however, all involve loss of energy:
Contact with cold item

31. Phase Changes Equilibrium
trapped molecules reach a balance between evaporation & condensation

32. Deposition
Deposition – changing from gas directly to solid
Snowflakes

33. Freezing Freezing – process of changing from liquid to solid
Remove energy from liquid
Molecules don’t move past each other any longer
Molecules stay in fixed, set position
Become solid

34. Phase Changes Energy Required Energy Released Solid  Liquid
Melting or fusion
Liquid  Solid
freezing
Liquid  Gas
Vaporization, evaporation or boiling
Gas  Liquid
condensation
Solid  Gas
sublimation
Gas  Solid
solidification

35. Phase Diagrams
Phase diagram shows phase of matter at different temperatures and pressures
Each substance is unique
X-axis usually temperature
Y-axis usually pressure
There is usually a “Triple Point” where all three phases can coexist
“Critical Point” – temperature and pressure above which substance cannot exist as liquid

36. Phase Diagram - Water

37. Phase Diagram CO2

38. Heating Curves
Kinetic Energy Changes – Heat Energy speeds up the molecules.
Potential Energy Changes – Heat energy separates the molecules from solid to liquid, liquid to gas.

39. Heating Curves Temperature Change change in KE (molecular motion)
depends on heat capacity
Heat Capacity
energy required to raise the temp of 1 gram of a substance by 1°C

40. Phase Change
The energy involved in a phase change is calculated using:
Heat of Fusion (Hfus)
Heat of Vaporization (Hvap)

41. Heat of Fusion
Heat of Fusion is the energy required to change 1 gram of a substance from the solid to the liquid state without changing its temperature.
Heat of Fusion is used for calculations involving the phase changes of solid  liquid or
liquid solid

42. Heat of Vaporization Heat of Vaporization (Hvap)
energy required to boil 1 gram of a substance at its b.p.
EX: sweating, steam burns, the drinking bird