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# 7th Grade Chapter 5 Lesson 3 Slideshare

## on Feb 11, 2008

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## 7th Grade Chapter 5 Lesson 3 SlidesharePresentation Transcript

• Pgs. 168- 177 For Student Use Only 7 th Grade Chapter 5 Lesson 3
• Ocean of Air
• How are fish at the bottom of the ocean different from fish at the surface?
Pressure is in the ocean and in the sky. Air pressure is the force of air pushing down on you.
• Air is a mixture
• Nitrogen- most abundant (78%)
• Oxygen- next abundant (20%)
• Carbon Dioxide
• Ozone
• Water Vapor
• What air does:
• Helps sound travel
• Oxygen helps us breathe and have fire
• Nitrogen dilutes oxygen in the air
Ocean of Air
• Ocean of Air
• Properties of Air:
• Gases (and liquids) are fluids
• Fluids= a substance that flows from one area to another
• Why are water and air different?
• Water’s molecules are close together and stick together
• Air does not stick together and are far apart
• Ocean of Air
• Properties of Air
• Gases expand to fill container
• Liquid Vs. Air
• Liquid- def. vol. but NO def. shape
• Air- NO def. shape and NO def. Volume
• Diffusion- the random spreading of one fluid throughout another
• Ocean of Air
• Gas Laws
• Boyle’s Law
• Charles Law
• Combined Gas Law
• Boyle’s Law
• Boyle’s Law states:
• If the Temperature of a gas remains constant, its volume and pressure are inversely related
• If volume goes up, pressure goes down and vice versa
• Explain this principle in everyday terms. (Use an example)
• Charles’s Law
• Charles’s Law states:
• If the pressure of a gas remains constant, its volume and temperature are DIRECTLY related
• If temperature increases the volume increases and vice versa
• Explain this principle in everyday terms. (Use an example)
• Other Information
• Air expands when heated!
• Air contracts when cooled.
• Cooler air sinks
• Warmer air rises
• Combined Gas Law
• Combined Gas Law states:
• If the volume of a gas is held constant its pressure and temperature are DIRECTLY related
• If pressure increases so does the temperature and vice versa
• Explain this principle in everyday terms. (Use an example)
• Other Information
• Air Pressure
• Atmospheric Pressure:
• Air pressure is more than one ton at sea level, but your body also pushes outward
• Layers of Atmosphere:
• Troposphere- lowest layer- where gravity pulls all the air
• Stratosphere
• Mesosphere
• Thermosphere
• Exosphere
• Air Pressure
• Measuring Air Pressure
• Barometer- what is used to air pressure
• Torricelli- invented first barometer- used a long glass tube to measure air pressure
• Pascal- figured out that the higher you went the less air would push down and the more mercury would run out of the tube- he was right
• Meteorologists
• Meteorologists:
• Measure air pressure to help predict weather
• Normal average air pressure at sea level is 29.92 inches of Hg
• Air pressure may actually very.