Originally created by Emily AdamsonEdited 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:VibrationalRotationalTranslational.

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 becausethe 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!

Overall, when temperature increases, atoms andmolecules’ motion increases (kinetic energy).Thermal energy increases because the total

amount ofkinetic energy increased due to the temperature

change.

THEY’RE ALL INTERTWINED!

3 STATES OF MATTER

SOLIDLIQUIDGAS

SOLIDSFixed shape and volumeNormally hard and rigidLarge force needed to change shape

High densityIncompressible

Model of SolidsClosely packed

togetherOccupy minimum

spaceRegular patternVibrate about fixed

positionNot free to move

about

LIQUIDSLIQUIDSFixed volume but no fixed shape

High densityNot compressible

Model of LiquidsOccur in clusters with molecules slightly further apart as compared to solids

Free to move about within confined vessel

GASESGASESNo fixed shape or volume

Low densityCompressible

Model of GasesModel of GasesVery far apartTravel at high speeds

Independent and random motion

Negligible forces of attraction between them

Brownian Brownian MotionMotionMovement of smoke

under the microscopeRandom motionHigh concentration to

low concentration until uniform (all the same = homogeneous)

Increases with increasing temperature (thermal energy)

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.

F

The force per unit area is the pressure exerted on the wall.

Air molecules in a container will exert a certain amount of pressure.

Pressure-volume (P-V)relationship of a gasAir 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 gasTherefore, when we decrease the volume of the container, the pressure exerted by the air molecules on the container increases.

V

1P

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=

p2= 900 Pa

(1000)

)(600)(1500

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.

From the applet, we can see that

Pressure increases as the temperature increases.

TP when the volume is kept constant

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 RelationshipThis 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.

TV at constant pressure

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