1. Air Pressure
The Air Around You

2. Weather
Weather- The condition of Earth’s atmosphere at a particular time and place
Atmosphere- is the envelope of gases that surrounds the plant

3. Composition of the Atmosphere
Earth’s atmosphere is made up of
nitrogen
oxygen
carbon dioxide
water vapor
Nitrogen is the most common gas in the atmosphere

4. Altitude and the Properties of Air
Air Pressure- the result of the weight of a column of air pushing down on an area
Altitude- elevation or the distance above sea level.
Air pressure is greater at sea level because sea-level air has the weight of the whole atmosphere pressing on it.

5. Video Link

6. Air Pressure
Can you feel it?

7. Air Pressure
Air pressure is the measure of the force with which air molecules push on a surface.
Air Pressure is GREATEST at the surface of Earth because there is more of the atmosphere above you to push down on you.

8. Air Pressure is like blankets
When you’re at sea level it’s like you’re under ______ of blankets.
When you’re on a tall mountain it’s like you’re under ________ blankets
Prompt students to write into the blanks in their notes. Have them read the completed sentences to a partner.

9. As you move UP through the atmosphere, air pressure decreases.

10. Air Pressure is dependant on DENSITY
More dense air will have a higher air pressure- there are more air molecules in a given space to push down on you
Less dense air will have a lower air pressure- there are fewer air molecules to push down on you.
More Dense= more particles to push down on you
Less Dense= fewer particles to push down on you

11. Air Pressure is affected by 3 factors
1- Elevation, or altitude
2- Temperature
3- Water content

12. Impact of Elevation on Air Pressure
As you move up through the atmosphere, air pressure decreases.
There are fewer air molecules above you to push down on you, so the force of the air will be less.

13. Impact of Water Content, or humidity, on Air Pressure
Moist air is less dense than dry air, and therefore has a lower air pressure.
A water molecule has less mass than other molecules that make up the air. If you replace some of the air molecules with water molecules, the water lowers the density (and lowers the air pressure) N
H2O N O
Weighs less since H2O is lighter than Nitrogen and Oxygen O
H2O O N

14. Impact of Temperature on Air Pressure
Warm air is less dense than cold air. Therefore, warm air has a lower air pressure and cold air has a higher air pressure.
The molecules in warm air are moving fast and are spread farther apart. Therefore there are fewer air molecules in a given area to push down on you.
Warm
Air
Cold Air

15. Barometer
The piece of equipment used to measure air pressure is a Barometer
Mercury Barometer
Aneroid Barometer

16. Mercury Barometer

17. Air Pressure Affects the Weather
Air pressure in a weather system reflects the amount of water in the air, which affects the weather.
Low air pressure usually results in Bad weather: stormy, cloudy, overcast.
High air pressure usually results in Good weather: clear skies, no precipitation

18. Cold Air High Pressure looks like this in weather: Creates
What would the air molecules look like? How does the density of the molecules affect the amount of pressure? Why would that create nice weather?
Prompt students to write answers in their power point notes.

19. Low Pressure Hot Air Creates Low Pressure looks like this in weather:
What would the air molecules look like? How does the density of the molecules affect the amount of pressure? Why would that create nice weather?
Prompt students to write answers in their power point notes.

20. Air Pressure on a Weather Map
Areas of High and Low pressure on shown on a weather map with an H or an L.

21. Your Turn! Compare and Contrast
What is low and high pressure? What are their causes? How are they different or the same?
Complete the worksheet. Make sure you include both diagrams and writing. Fill out the whole sheet. It is worth 5 points.
Hand out air pressure worksheet.

22. Heat Transfer in the Atmosphere
Thermal Energy – heat energy
Heat- the transfer of thermal energy from a hotter object to a cooler one.
Heat is transferred in threes different ways
Radiation
Conduction
Convection

23. Radiation Conduction Convection
the direct transfer of energy by electromagnetic waves
warmth of the sun’s rays on your face
Conduction
The direct transfer of heat from one substance to another that it is touching
Heat from a stove to a put
Convection
The transfer of heat by the movement of a fluid
Boiling water