1. Why do your ears pop?
Your ears pop in air planes because the air high above the surface of Earth is less dense than air near the surface, because air near the surface has all the air above it pushing down.
As you ascend in an airplane and the air pressure decreases, the air trapped in your inner ear will cause your eardrums to push outward.  This expansion causes not only the discomfort you feel before your ears "pop," but also a decrease in hearing ability, because the pressure on your ears drums makes the sound harder to transmit.
Your body can equalize the pressure between your inner ear and the atmosphere by allowing some air from your inner ear to escape through the Eustachian tubes, two small channels that connect the inner ears to the throat, one on each side.
When they open, you feel the pressure release and you hear the change because it�s happening in your ear.  This equalization of pressure is the "pop.“
On the way down from an air plane flight, the air pressure increases, while your inner ear is still at the lower pressure it has adjusted to.  Now, the extra pressure pushes the eardrums inward.
Eventually, the pressure will equalize again, but many people don�t wait, they just hold their nose closed, close their mouth and blow.  Because the air from their lungs has nowhere to go, it is forced into the inner ear through the Eustachian tubes, "popping" their ears.

2. Gas Pressure Lesson Objectives Explain what causes gas pressure
Describe how the pressure of a gas can be changed.
Explain a change in gas pressure in terms of particles.
Give some examples of the effects of air pressure.

3. Review: Particle Model
With the person next to you:
Describe the particle model for either a solid, liquid, or gas but DON’T tell them which one it is!
Your partner will have to guess which one you are describing.
Then switch roles.
Check green sheet, collect homework

4. Gases Gases have very special properties.
They move about very fast in all directions and spread very far apart.
What happens when they reach the sides of the container?

5. What happens all the time?
Imagine bumper cars moving around in all random directions very quickly.
What happens all the time?
COLLISION!

6. Pressure
Gas particles are constantly bumping into each other and the walls of the container.
Pressure is the force caused by particles colliding with objects. ES7 p. 100, A1

7. Example: Balloon What is happening when you blow up a balloon?
Think about what is happening with the gas particles. ES7 p. 100, A2
Think about the number of collisions happening inside and outside of the balloon.

8. Effects of Pressure If you add more gas particles inside…
There is more pressure on the inside of the balloon…
And the balloon expands.
When the pressure outside and inside is the same the balloon stops expanding.

9. Effects of Pressure What happens when you remove gas particles?
Less pressure inside…
The object shrinks or something will move in to try to fill the space.
If you suck all the particles out of something it is called a vacuum (empty space).

10. Two things affect the amount of pressure.
The number of collisions
The force of the collisions
What changes the pressure?
The number of particles
How fast the particles are moving
Size of container (affects number of collisions)

11. What affects pressure?
Pressure is force from particles bumping into objects.
What changes how much pressure there is?
Speed of particles
Amount of particles
Size of the container

12. Explain How Each of these Effect the Amount of Pressure
Speed of particles
Amount of particles
Size of the container

13. Higher or Lower?
For the following situations tell if the pressure is Higher (hold up red card) or Lower (hold up green card) than before.

14. Gas particles are put into a larger container.
High or Low?
Gas particles are put into a larger container.
lower

15. A container of gas is heated.
High or Low?
A container of gas is heated.
higher

16. You make the container smaller.
High or Low?
You make the container smaller.
higher

17. High or Low?
Blowing up a balloon (inside the balloon).
higher

18. Pumping out air from a bottle.
High or Low?
Pumping out air from a bottle.
lower

19. Pressure Demonstration
Draw the demonstration.
Discuss with your group and come up with an explanation for what we saw happen.
Each person in the group needs to be able to describe the explanation to me.

20. The water stays in because the pressure from air particles outside is the same as the pressure from the water particles inside the cup. WHY?
More water particles (particles closer together) but they move much slower  more collisions but with less force.