Air PressureAir PressureAim: What is air pressure?Aim: What is air pressure?

Do Now:Do Now:• What happened to this cup?

1. What is air pressure?1. What is air pressure?• Air pressure is the force of air

pushing down on us.

• Air is pulled down to earth by gravity.

• http://kids.earth.nasa.gov/archive/air_pressure/

1. Hot air balloons1. Hot air balloons• Observe how air pressure affects a ri

sing weather balloon.• http://kids.earth.nasa.gov/archive/air

_pressure/balloon.html

• As the balloon rises higher, the air pressure decreases on outside, allowing the balloon to expand and rise.

Air Pressure DemosAir Pressure Demos• http://www.youtube.com/watch?

v=JPbT6Z97b20• http://www.youtube.com/watch?

v=OHY9fFQhX68&feature=related• http://www.youtube.com/watch?

v=RPlCO3AITV4&feature=related• http://www.youtube.com/watch?

v=ctJyu5ete6Y• http://www.youtube.com/watch?

v=mT6YEXhqIAk&feature=related

2. How is air 2. How is air pressure measured?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

• http://www.upscale.utoronto.ca/GeneralInterest/Harrison/Barometer/Barometer.html

3. Air pressure and 3. Air pressure and Temperature changes at Temperature changes at

different altitudesdifferent altitudes

• mountain vs. beach

4. Mountain vs. Beach4. 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)

5. Sea level air 5. Sea level air pressurepressure

• 29.92 inches of mercury

• 1013.2 mb• 1 atmosphere• Any number above

is considered High pressure, below is Low pressure

6. How does a barometer 6. How does a barometer help forecast the weather?help forecast the weather?

• Rising barometer = higher air pressure = weather will improve (good weather)

• Falling barometer = lower air pressure = worse weather

• http://kids.earth.nasa.gov/archive/air_pressure/barometer.html

• Examine how barometric pressure changes with weather conditions.

7. Weather vs. Climate: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.

8. Summary: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

Alvin Rover ….Atlantis Alvin Rover ….Atlantis expedition 2006.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.