Pre-University Chemistry

1. Chapter 10: States of Matter
• Kinetic Molecular Theory: the idea that
particles of matter are always in motion;
this applies to all states of matter
• Used to explain properties of matter in
terms of energy

2. Ideal Gas
= hypothetical gas that perfectly fits all 5 assumptions of
the Kinetic Molecular Theory:
1) Gases consist of a large # of particles that occupy a
larger space with respect to their relative sizes thus
gases can be easily compressed
2) Collisions b/t particles and walls are perfectly elastic
( = no loss of KE)
3) Gas particles are in rapid, random, constant motion
4) There are no forces of attraction b/t gas particles
5) Temperature of a gas depends on the average
KE of the particles; directly proportional
A gas that is always a gas - Doesn’t exist!

3. Characteristics of Gases
• Expansion: no definite shape or volume; fill any container,
regardless of shape
• Fluidity: particles slide easily over one another; act like
liquids, thus they are both fluids
• Low Density and Compressibility: volume can be
decreased greatly
• Diffusion: since gases are always randomly moving, freely
mix together with other gases
• Effusion: process by which gases move out of a small
opening; molecules with low mass effuse more quickly than
those with larger masses
KE= ½ mv2

4. Liquids
• Least common state of
matter in universe; not so
on Earth
• Operate at slim range of
temps/pressures
• Volume, shape, density?
• Particles in constant
motion, and closer than
those of a gas (d/t
intermolecular forces

5. Other Characteristics of liquids:
• Have a very high density when compared to
gases; depends on temperature  lower
temp…except for water
• Not easily compressed
• Easily diffuse in other liquids it can dissolve
in d/t… much slower than it is in gases –
why?

6. Surface Tension
• All liquids exhibit surface
tension = a force that tends to
pull adjacent particles at a
liquids surface together,
decreasing its surface area to
the smallest possible size;
meniscus
• Results from… water shows
high surface tension
• Capillary action = attraction of
a liquid to a solid; rises in a
small tube against gravity

7. Surface Tension
Look at the picture below. The milk forms small droplets that
resemble a crown. But why does this happen?
Because of the surface tension of water, which keeps the
droplets spherical.

8. Some terms:
solid liquid gas
MELTING BOILING
FREEZING CONDENSATION
0ºC 100ºC
melting/freezing point boiling/condensation point
(ice) (steam)(water)
SUBLIMATION

9. More info on Liquids
• Vaporization – liquid to
gas
• Evaporation – escape
from a non-boiling
liquid at its surface
• Boiling – vaporization
through the entire liquid
• Freezing – physical
change from liquid to
solid through the loss
of HEAT. Evaporation- a beautiful process.

10. Solids
• Particles in a solid are tightly-
packed together due to attractive
forces. Highly-ordered.
• Atomic/molecular motion is
restricted, but it occurs.
• 2 types:
1) Crystalline: consists of crystals
(orderly, geometric, repeating
pattern)
2) Amorphous: particles are
randomly arranged
Sodium Chloride crystals
Amorphous solid

11. Properties of solids
• Definite shape and volume
• Definite melting point (d/t addition of heat)
• High density and incompressible
• Low rates of diffusion

12. Crystals
• Arranged in a lattice structure
• Smallest unit of a crystal that shows the 3-
D pattern of the lattice = UNIT CELL

13. Changes of State
• Phase = any part of a
system that has a
uniform composition
and properties
• Condensation =
process by which a
gas turns into a liquid
• Vapor = a gas in
contact with its liquid
or solid phase

14. Vapor Pressure
• The pressure exerted by a vapor that is in
equilibrium with its corresponding liquid
• Develops in a closed system
• Increase AKE, increase particles leaving
liquid, increased pressure
• Volatile liquids evaporate
easily d/t weak IMF

15. Vapor Pressure

16. Notes on Boiling Point
• BP = when vapor pressure
equals atmospheric pressure
• Increase pressure, increase
BP = pressure cooker
• Molar Enthalpy of
Vaporization = amount of
heat needed to vaporize 1
mole of a liquid at the liquid’s
BP at a constant pressure; the
stronger the attraction….
• Vapor pressure is directly
proportional to temperature
• Vacuum evaporator – how
does it work?

17. Freezing and Melting
• Definitions?
• What is the difference b/t freezing water
and ice? Boiling water and steam?

18. Do Now
• Explain the importance and significance of
this graph…

19. More Vocab
• Molar Enthalpy of Fusion = the amount
of heat required to melt one mole of a
solid
(40.79 kJ/mol for water)
• Sublimation vs. deposition

20. Phase Diagrams
graph of pressure vs. temperature that shows the conditions
under which the phases of a substance would exist

21. Water
• Most abundant liquid
on Earth; essential to
life; most reactions
take place in it
IMPORTANT!!!
• Review its structure
and properties…

22. Water