Air Pressure. Learning Objectives Identify some properties of air. Describe how barometers can be...
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Transcript of Air Pressure. Learning Objectives Identify some properties of air. Describe how barometers can be...
Learning Objectives Identify some properties of air. Describe how barometers can be used to measure air
pressure. Explain how altitude affects air pressure and density.
Properties of Air
What is density?• The amount of mass in a given volume of air• Calculate by dividing its mass by its volume
What is air pressure?• Pressure- is the force pushing
on an area or surface• Air pressure- is the result of
the weight of a column of air
pushing on an area
What Instruments Measure Air Pressure?Barometer – is used to measure air pressure•2 types of barometer
• Mercury Barometer• Consists of a long glass tube that is closed at one
end and open at the other• Aneroid Barometer
• An airtight metal chamber that is sensitive to change in air pressure
Changes in Air Pressure
Describe what happens when air pressure decreases.
High air pressure: as air pressure increases, it pushes down on the surface of the mercury in the dish. This causes the mercury tube to rise
Low air pressure: as the air pressure drops, the mercury in the tube falls, and the mercury in the dish rises
Units of Air PressureMost weather reports use inches of mercury as the unit of air pressure.
30 inches of mercury
40 inches of mercury
15 inches of mercury