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Air Pressure

Air Pressure. Air Pressure. A ir consists of atoms And molecules Which both have mass. Because air has mass, it also has other properties, including density and pressure. . Air Pressure. Density is the amount of mass in a given volume.

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Air Pressure

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  1. Air Pressure

  2. Air Pressure • Air consists of atoms • And molecules • Which both have mass. • Because air has mass, it also has other properties, including density and pressure.

  3. Air Pressure • Density is the amount of mass in a given volume. • You can calculate density by dividing mass by volume.

  4. Air Pressure • Pressure is the force pushing on an area or surface. • A denser substance has more mass than a less dense one. • So denser air exerts more pressure than less dense air.

  5. Air Pressure Air pressure is the result of the weight of a column of air pushing down on an area. There is a column of air above you all the time. The weight of the air in the atmosphere causes air pressure.

  6. Measuring Air Pressure • Have you ever heard a weather report say that the air pressure is falling?

  7. Measuring Air Pressure • Falling air pressure usually indicates that a storm is approaching. • Rising air pressure usually means that the weather is clearing.

  8. Measuring Air Pressure • A barometer is an instrument that is used to measure changes in air pressure. • There are two kinds of barometers: • mercury barometers • aneroid barometers

  9. Measuring Air Pressure • A mercury barometer consists of a glass tube open at the bottom end and partially filled with mercury.

  10. Measuring Air Pressure • The word aneroid means “without liquid.” • An aneroid barometer has an airtight metal chamber. • The metal chamber is sensitive to changes in air pressure. • As the shape of the chamber changes, the needle on the dial moves.

  11. Measuring Air Pressure

  12. Increasing Altitude • Altitude, or elevation, is the distance above sea level. • Sea level is the average level of the surface of the oceans. • Air pressure decreases as altitude increases. • As air pressure decreases, so does density.

  13. Altitude Affects Air Pressure   • Imagine a stack of ten books. Which book has more weight on it, the second book from the top or the book at the bottom? • Air at sea level is like the bottom book. • Air near the top of the atmosphere is like the second book from the top.

  14. Altitude Also Affects Density   • If you were near the top of a mountain and tried to run, you would get out of breath quickly. • Why would you have difficulty breathing at high altitudes? • As you go up through the atmosphere, the air pressure decreases. • As air pressure decreases, the density of the air decreases.

  15. Pressure and Density based on Elevation

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