1. Air Pressure Explained
What about on a plane?
… or maybe when you dive deep into a pool?
Could air pressure ever make you feel like this guy?

2. See how SPREAD APART the molecules are?
Characteristics of Warm Air
*Warm air rises
*is less dense (Look at the picture below)
*particles are spread far apart
*particles have lots of energy so the move rapidly
*Warm air has low pressure
See how SPREAD APART the molecules are?

3. See how CLOSE TOGETHER the molecules are when they get cold?
Characteristics of Cold Air
*Cold air sinks
*is more dense (Look at the picture below)
*particles have very little energy so they move slowly
*Cold Air particles are close together
*Cold air has high pressure
See how CLOSE TOGETHER the molecules are when they get cold?

4. Okay- let’s review the difference between warm and cold air.
Warm Air
Cold Air
Particles are spread far apart
Is less dense
Rises
Particles are close together
Is dense
Sinks

5. Wait, just what IS air pressure anyway?
Air Pressure is the force exerted on the Earth by the weight of tiny air molecules.

6. Who is feeling more pressure exerted on them, Sarah or Ben?
WARM AIR
COLD AIR
Who is feeling more pressure exerted on them, Sarah or Ben?
WHY?

7. Because cold air is more dense, and sinks, it exerts HIGH PRESSURE.
Warm air is less dense, rises, and exerts LOW PRESSURE.
WARM AIR
COLD AIR

8. Weather maps on t.v. show us where there are areas of high and low pressure.

9. NO NOTE-TAKING on THIS PAGE!
Low Pressure
NO NOTE-TAKING on THIS PAGE!
A low pressure system on a weather map is an area where the air pressure is lower than the surrounding air.
Because of this pressure difference, warm, humid and less dense air is forced upward by the surrounding higher pressure air, swirling counterclockwise as it rises. L L
Click on the raindrop to see an animation of low pressure.

10. NO NOTE-TAKING on THIS PAGE!
As warm moist air rises, condensation & clouds form.
Low pressure is associated with warm, & humid/rainy weather.
NO NOTE-TAKING on THIS PAGE! L
Low Pressure

11. NO NOTE-TAKING on THIS PAGE!
High Pressure
NO NOTE-TAKING on THIS PAGE!
A high pressure system on a weather map is an area where the air pressure is higher than the surrounding air.
Because of this pressure difference, cool, dry and more dense air flows into the lower pressure area, blowing out over a great area. H H

12. NO NOTE-TAKING on THIS PAGE!
As cool air sinks, only a few sparse clouds may be in the sky.
High pressure is associated with cool & dry/sunny weather. H
High Pressure

13. Compare the forces needed to tighten and loosen the screw.
How do you remember the direction for pressure systems?
Use the screwdriver to turn the screw into the board.
Which direction are your hand and the screwdriver turning?
2. What is happening to the screw as
you are turning your hand?
Use the screwdriver to loosen the screw from the board.
3. Which direction are your hand and
the screwdriver turning?
4. What is happening to the screw as
Compare the forces needed to tighten and loosen the screw.
How was the experience of rotating the screw into the board similar to pressure systems?

14. THESE ARE THE NOTES FOR YOUR T-CHART!
Let’s Compare!
Low Pressure
High Pressure
Air tends to rise
Warm, less dense air
Winds swirl counterclockwise
Warm, humid
Cloudy, rainy weather expected
Air tends to sink
Cool, dense air
Winds swirl clockwise
Cool, dry
Sunny, clear skies
THESE ARE THE NOTES FOR YOUR T-CHART!