1. Aim: What is air pressure?

2. Do Now:
What happened to this cup?

3. 1. What is air pressure?
Air pressure is the force of air pushing down on us.
Air is pulled down to earth by gravity.

4. 1. Hot air balloons
Observe how air pressure affects a rising weather balloon.
As the balloon rises higher, the air pressure decreases on outside, allowing the balloon to expand and rise.

5. Air Pressure Demos http://www.youtube.com/watch?v=JPbT6Z97b20

6. 2. How is air pressure measured?
A barometer is used to measure air pressure.
Mercury barometer -The air pushes down on the mercury and forces mercury up the glass tube. Aneroid barometer – metal chamber (aneroid) connected to a dial. Aneroid = “without liquid” Pressure expands and contracts the metal

7. 3. Air pressure and Temperature changes at different altitudes
mountain vs. beach

8. 4. Mountain vs. Beach
At high altitude (mountain), the air pressure decreases and the temperature decreases (gets colder).
At low altitude (beach), the air pressure increases and the temperature increases (gets warmer)

9. 5. Sea level air pressure 29.92 inches of mercury 1013.2 mb
1 atmosphere
Any number above is considered High pressure, below is Low pressure

10. 6. How does a barometer help forecast the weather?
Rising barometer = higher air pressure = weather will improve (good weather)
Falling barometer = lower air pressure = worse weather
Examine how barometric pressure changes with weather conditions.

11. 7. Weather vs. Climate:
Weather is the mix of events that happens each day in our atmosphere.
Climate is the average weather in a place over many years.
Example: the climate of a desert is hot and dry…but there are days that it can rain.

12. 8. Summary: Air pressure changes…it is not the same everywhere.
Air pressure contributes to the weather conditions.
How does air pressure affect your life?
Affects the weather
Need a certain air pressure to breath
Allows us to forecast the weather

13. Alvin Rover ….Atlantis expedition 2006.
The Styrofoam cup was aboard a deep ocean roving vessel.
The pressure was SO HIGH under the ocean that all the air was squeezed from the Styrofoam and shrank the cup.