1. Kinetic Molecular Theory
All matter is made of atoms or molecules that are in constant motion
These particles contain energy
The movement of these particles is random
VIDEO CLIP

2. Gases

3. Properties of Gases Gases have mass
Gases take shape & volume of their container
Gases are compressible (because they are separated by great distances)
Gases move through each other easily
“Diffusion”
perfume, skunks!
Gases exert pressure

4. Pressure Gas molecules hit walls of container, exerting a force
Pressure depends on
Number of impacts (collisions) per unit time
Force of each impact

5. Barometer animation

6. What is air pressure?
pressure exerted on us by weight of gases above our heads (& all around our body)
at sea level:
air pressure = 1 atmosphere (atm)
= 760 torr
= 760 mmHg
= kPa

7. When we talk about gases, we use a model to show how it would “ideally” behave.
The model = Kinetic Molecular Theory Of Gases
Under the KMT, we make 4 assumptions about the behavior of Gases

8. Kinetic Molecular Theory of Gases
Particles move in rapid, random, straight line motion
ELASTIC Collisions = When they hit one another and the walls of their container, they do not lose potential energy – they do not slow down
They are separate by great distances (the gas is mostly empty space) therefore the volume of the gas molecule is negligible
Gas molecules do not attract or repel one another

9. Real vs. ideal gas Ideal gas obeys all assumptions of KMT all the time
It’s a model
It doesn’t exist
Real gases
Molecules really do have volume
And molecules will interact, especially at
high pressure & low temperature
NOTE: when molecules are close together they will interact and could possibly condense
LINK

10. High pressure – Look what happens to this gas

11. Low temperature– Look what happens to this gas

12. When we measure the temperature of a gas, we are measuring the average kinetic energy of the particles