1. Air Pressure Graphics

2. Air Pressure (pgs. 10-14) I.Properties of Air A.Atmosphere is constantly pressing down on you. B.Air seems to have no mass 1.Air is made of atoms so must have mass 2.Air must have density and pressure too C.DENSITY 1.DEF: Amount of mass in a given volume. 2.Density = Mass/Volume 3.more molecules in a volume = more density 4.less molecules in a volume = less density More Molecules Less Molecules EXAMPLES Metals Stone EXAMPLES Wood Foam Air AIR PRESSURE GRAPHICS

3. D.PRESSURE 1.DEF: Force pushing on a surface 2.AIR PRESSURE: Weight of a column of air pushing down on an area. 3.Weight of air on us is as much as a bus 4.Air pushing down is balanced by air pushing up 5.Air pressure changes from day to day 6.Denser air has more pressure

4. D.PRESSURE 1.DEF - Force pushing on a surface 2.AIR PRESSURE: DEF - Weight of a column of air pushing down on an area. 3.Weight of air on us is as much as a bus 4.Air pushing down is balanced by air pushing up and in all directions 5.Air pressure changes from day to day 6.Denser air has more pressure

5. Pressure and Air Pressure Any force pushing on a surface exerts pressure The atmosphere presses down on the surface of the Earth due to _________ _______________________________________________________________ Gravity pulling down on all the mass of air above us. AIR PRESSURE GRAPHICS

6. 62 miles How Much Air? The number of air molecules pressing down on the surface is the same as the number of water molecules pressing down on the bottom of a 33 feet deep pool. 33 feet Pool Air Pressure changes exactly the same as Air Density More dense copper block on your head “weighs” more than less dense wood block.

7. Air pushing on all sides is balanced by the force of air pushing out. DRAW Equal #’s of arrows on both sides They should line up to show balance

11. http://www.youtube.com/watch?v=7vPON- i5pm8 http://www.youtube.com/watch?v=7qXYkL UKso4

12. D.PRESSURE 1.DEF - Force pushing on a surface 2.AIR PRESSURE: DEF - Weight of a column of air pushing down on an area. 3.Weight of air on us is as much as a bus 4.Air pushing down is balanced by air pushing up and in all directions 5.Air pressure changes from day to day 6.Denser air has more pressure Air pushing on all sides is balanced by force pushing out. DRAW Equal #’s of arrows on both sides They should line up to show balance

13. II.Measuring air pressure A.BAROMETER: used to measure air pressure B.MERCURY BAROMETER: glass tube open at the bottom and partially filled with mercury. 1.Air pushes down on mercury in dish and forces it upward. 2. More pressure = higher mercury 3. Sea Level has 76 cm (35 in) C.ANEROID BAROMETER: 1.an airtight metal chamber “without liquid” that senses change in air pressure 2.Higher pressure - Chamber walls are pushed in, the dial goes up Just like a bathroom scale… D.Units of air pressure 1.Inches of mercury (30 inches average) 2. Millibars (1016 milllibars average)

14. II.Measuring air pressure A.BAROMETER: used to measure air pressure B.MERCURY BAROMETER: glass tube open at the bottom and partially filled with mercury. 1.Air pushes down on mercury in dish and forces it upward. 2. More pressure = higher mercury 3. Sea Level has 76 cm (35 in) C.ANEROID BAROMETER: 1.an airtight metal chamber “without liquid” that senses change in air pressure 2.Higher pressure - Chamber walls are pushed in, the dial goes up Just like a bathroom scale… D.Units of air pressure 1.Inches of mercury (30 inches average) 2. Millibars (1016 milllibars average)

15. Mercury Barometer: The weight of the column of mercury is equal to the weight of the column of air (air pressure) Weight of mercury column = to weight of air

16. Aneroid Barometers are just like a bathroom scale that measures the weight of the air instead of body weight.

17. II.Measuring air pressure A.BAROMETER: used to measure air pressure B.MERCURY BAROMETER: glass tube open at the bottom and partially filled with mercury. 1.Air pushes down on mercury in dish and forces it upward. 2. More pressure = higher mercury 3. Sea Level has 76 cm (35 in) C.ANEROID BAROMETER: 1.an airtight metal chamber “without liquid” that senses change in air pressure 2.Higher pressure - Chamber walls are pushed in, the dial goes up Just like a bathroom scale… D.Units of air pressure 1.Inches of mercury (30 inches average) 2. Millibars (1016 milllibars average)

18. III.Altitude and the Properties of Air A.ALTITUDE: or elevation, is the distance above sea level. 1.Air pressure decreases as altitude increases. 2.Air pressure decreases as air density decreases. B.Altitude affects air pressure 1.Air pressure like a stack of books. More weight is on the bottom than the top. 2.Sea level is the bottom book. C.Altitude also affects density 1.Molecules are farther apart at altitude. 2. Farther apart means less dense. 3.Out of breath since there is less air. Why do your ears pop going uphill? As you go uphill there is less air around you which means less air density and less air pressure to push on you. LESS MORE

19. Air Pressure Analogy Sea level is like the bottom book More weight is on the bottom book than the top Top of the atmosphere is like the top book

20. Table of Contents Entry # TITLEPAGE # 4 Seasons Re-Write 5 Modeling Changes in Air Pressure

21. Modeling Changes in Air Pressure 1. How can air pressure change? A. Decreasing air pressure 1) Increase in elevation as you go higher 2) A low pressure system approaching (hurricane…) 3) Increase in temperature When outside air pressure is reduced, the internal pressure wins and pushes balloon out making it bigger

22. Modeling Changes in Air Pressure B) Increasing air pressure 1) Decrease in elevation as you go lower 2) A high pressure system approaching 3) Decrease in temperature When outside air pressure is increased, the outside pressure wins and squeezes balloon smaller.