Originally created by Emily Adamson
Edited by M.Elizabeth
What’s the Kinetic Theory of Matter?
It’s a theory that helps explain difference between
the states of matter.
The Kinetic Theory of Matter states…
Matter is made up of constantly moving molecules
or atoms.
Under the Kinetic Theory of Matter…
Solids’ particles are so close to each other that they
only vibrate in place.
Under the Kinetic Theory of Matter…
Liquids’ particles have more space to move than
solids, but there is still an attraction between
them.
Under the Kinetic Theory of Matter…
Gases’ particles are far apart and move around
because the attraction is so low it can be
disregarded.
Substances can change into different phases of matter and
back.
WHY DOES THIS HAPPEN?
First, we need to know about….
Kinetic Energy is energy of motion. There are multiple forms, such as:
 Vibrational
 Rotational
 Translational.
First, we need to know about….
Thermal energy is total kinetic energy of all of a substance’s
atoms and molecules .
First, we need to know about….
Temperature is the average amount of kinetic
energy in an object.
Matter can change into different phases because
the exchange of thermal energy between a substance and the
environment. Forces that hold substances in one phase are
overcome with the addition of energy
Everything wants to be in its lowest state of energy. That’s
why the exchange occurs!
Thermal
Energy
Temperature
Kinetic
Energy
• Increases as temperature increases
• Increases as kinetic energy increases
• Increases as kinetic energy increases
• Increases as thermal energy increases
• Motion increases as temperature increases
• Increases as thermal energy increases
Overall, when temperature increases, atoms and
molecules’ motion increases (kinetic energy).
Thermal energy increases because the total amount of
kinetic energy increased due to the temperature
change.
THEY’RE ALL INTERTWINED!
KINETIC
THEORY
OF
MATTER
3 STATES OF MATTER
SOLID
LIQUID
GAS
SOLIDS
 Fixed shape and volume
 Normally hard and rigid
 Large force needed to change shape
 High density
 Incompressible
Model of Solids
 Closely packed together
 Occupy minimum space
 Regular pattern
 Vibrate about fixed
position
 Not free to move about
LIQUIDS
Fixed volume but no fixed
shape
High density
Not compressible
Model of
Liquids
 Occur in clusters with
molecules slightly
further apart as
compared to solids
 Free to move about
within confined vessel
GASES
No fixed shape or volume
Low density
Compressible
Model of Gases
Very far apart
Travel at high speeds
Independent and random
motion
Negligible forces of
attraction between them
Brownian Motion
 Movement of smoke
under the microscope
 Random motion
 High concentration to
low concentration until
uniform (all the same =
homogeneous)
 Increases with
increasing temperature
(thermal energy)
Pressure in Gases
(Ideal Gases)
Air molecules in a container are in
as state of continuous motion.
Pressure in Gases
(Ideal Gases)
Air molecules in a container are in
as state of continuous motion.
When they collide with the wall of
a container, they exert a force, F on
the wall.
F
Pressure in Gases
(Ideal Gases)
Air molecules in a container
are in as state of continuous
motion.
When they collide with the
wall of a container, they exert
a force, F on the wall.
The force per unit area is the
pressure exerted on the wall.
F
Pressure-volume (p-V)
relationship of a gas
Air molecules in a container
will exert a certain amount of
pressure.
Pressure-volume (P-V)
relationship of a gas
Air molecules in a container
will exert a certain amount of
pressure.
If the volume of this container
was to decrease, the air
molecules will have less space
to move about. This will result
in the molecules colliding with
the walls more frequently.
Pressure-volume (p-V)
relationship of a gas
Therefore, when we decrease the volume of
the container, the pressure exerted by the
air molecules on the container increases.
1
P
V
To form an equation,
p = k/V
pV = k (k is a constant)
p1V1 = p2V2
Where p1 and V1 are the initial pressure and volume,
And p2 and V2 are the final pressure and volume.
Example:
The volume of a fixed mass of gas at 600 Pa is 1500cm3.
What is the pressure if the volume is reduced to
1000 cm3 at constant temperature?
Solution:
Using the formula: p1V1 = p2V2
(600)(1500) = p2(1000)
p2=
(600)(1500 )
(1000)
p2= 900 Pa
P-T Relationship
Now we will keep the
volume of the
container constant.
We will investigate to
see how the pressure
will vary with
temperature of the
gas.
P-T Relationship
From the applet, we can see that
Pressure increases as the temperature increases.
P T
when the volume is kept constant
Example
Air is being trapped in a container of fixed volume. At room
temperature of 300 K, the pressure exerted by the gas is 100 Pa.
If the air in the container was heated to 600 K, what is the new
pressure exerted by the gas now?
Solution:
Since pressure is proportional to temperature, when temperature
increases, pressure should also increase.
Temperature increases by 2 times, so pressure should increase by
2 times.
New pressure = 100 x 2 = 200 Pa
V-T Relationship
This is the most commonly occurring relationship.
When gas gets heated, the amount of space that it occupies
expands.
So when temperature increase, volume would also increase.
Temperature is proportional to volume.
V T
at constant pressure
Example
A balloon is filled with gas, at a temperature of 300 K, to a
volume of 50cm3. If I want to expand the balloon to a volume of
150cm3, what is the temperature of the gas now? Assuming that
the pressure exerted by the gas does not change.
Solution:
Volume is proportional to temperature.
Since the volume has to be increased by 3 times, the
volume should also be increased accordingly.
Required temperature = 300 x 3 = 900 K