1. States of matter & the kinetic
molecular theory.
Matter is classified into 3 states or phases:
Solids, liquids & gases
The structure, arrangement
& movement of the particles
determines the state of the
substance.
Solids liquids & gases
1
2. Diffusion & Brownian motion
Diffusion and Brownian motion in liquids
and gases, provides proof of the
existence of particles in matter.
Diffusion is the movement of
particles from a region of high
concentration to lower concentration -
until there is even distribution of particles
throughout the gas or liquid.
NH3 & HCl diffusion
2
3. Brownian motion is the haphazard,
random motion of larger particles that
are being bumped by much smaller gas
or liquid particles – ones that can’t even
be seen under a microscope.
Brownian motion
3
4. Forces between particles
There are forces between the particles in
each of the states of matter.
Solids – strongest forces – vibratory
motion & held close together.
Liquids – weaker forces – further apart
& able to flow past one another
Gases – weakest forces – particles far
apart & move easily
in all directions
4
5. Phase changes
Matter can change from one state to
another by adding or removing energy –
usually in the form of heat.
Solid to gas – sublimation
Solid to liquid – melting
Liquid to gas – evaporation
Gas to liquid – condensation
Liquid to solid – freezing
5
6. Temperature & Phase changes
The temperatures at which phase
changes take place have specific
names:
Solid → liquid – melting point
Liquid → gas – boiling point
Gas → liquid – condensation point
Liquid → solid – freezing point
The state of a substance at a certain
temperature, is determined from its
melting or boiling points.
States of matter
6
7. Temperature & Phase changes
H2O at -5 0C means it is in the solid state
(ice) – since it is below the freezing point
of 0 0C.
H2O at 120 0C means it is in the gaseous
state (steam) since it is above its boiling
point of 100 0C.
Change of state
Change of phase
7
9. Heating curve for water:
This graph shows how the curve changes
during the phase changes & heating process.
Temperature
Time
0C
-10 0C
100 0C
M.P.
B.P.
ICE
WATER
STEAM
Heating ice
9
10. Kinetic molecular theory
This theory explains properties of solids,
liquids & gases, relative to the particles
making up matter & their movement.
Particles in each phase are in constant
motion and thus have a kinetic energy.
Particles move at different speeds, but at
the same temperature, they have the
same average kinetic energy.
Kinetic molecular theory 10
11. Kinetic molecular theory: solids
Solids have:
strong forces between particles
a size & shape
vibrate about a fixed point
repulsive forces – thus no compression
11
12. Kinetic molecular theory: liquids
Liquids have:
weaker forces of attraction
move more freely past each other
no fixed shape – shape of container
particles have different velocities
ave. Ek same throughout liquid
strong repulsive forces – no
compression
particles collide with each other &
walls of container – thus a pressure.
12
13. Kinetic molecular theory: gases
Gases have:
weak forces between particles
greater motion & thus more energy
random motion with elastic collisions
causing pressure
no repulsive forces – particles far
apart – easy to compress
particles move at different
speeds but ave. Ek is the
same.
Kinetic theory &
temperature
Energy in a gas
13
