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Essential Question: What is the significance of the atmosphere to the existence of life on earth?
pp. 392-407
The Atmosphere
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The Atmosphere
The atmosphere is the layer of gases and other particles that surround earth much like the peel of an apple covers it.
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Benefits of atmosphere for humans include:
• provides gases like oxygen
• traps heat energy from sun which keeps us warm and water in a liquid state
• protects from UV rays & most meteoroids
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Properties of Air in the Atmosphere
• Air in the atmosphere has density– Air has mass because
it is composed of atoms and molecules
– Air has volume because it takes up space
– density = mass/volume
• Air also has pressure– Air molecules push
on objects from all directions
– As altitude increases air pressure and density decrease because its molecules are spread farther apart
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Composition of the Atmosphere • Nitrogen 78%
• Oxygen 21%
• All other gases 1%
• Tiny solid and liquid particles of:
–dust
–smoke
–salt
–chemicals
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Structure of the Atmosphere
• Troposphere• Stratosphere• Mesosphere• Thermosphere
–Ionosphere–exosphere
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Troposphere
• 0-12 km above Earth’s surface
• Temperature varies– For every 1km of altitude increase, temp decreases
approx 6.5oC – Constant -60oC in upper troposphere
• Where weather occurs and most clouds
• Where hot air balloons travel
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Stratosphere
• 12-50 km above Earth’s surface
• Temp in lower stratosphere about -60oC– Warmer in upper stratosphere due to ozone
layer which absorbs ultraviolet radiation
• Where airplanes and weather balloons travel
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Mesosphere
• 50-80 km above Earth’s surface
• Temp drops to -90oC in outer mesosphere
• Where most meteoroids burn up– Seen from Earth as shooting stars (meteors)
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Thermosphere
• Everything 80km above Earth’s surface
• Temp up to 1,800oC
• Air very thin
• Includes the ionosphere and exosphere
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More on the Thermosphere
Ionosphere• 80-550km above
Earth’s surface• Radio waves
reflected from ionosphere to Earth
• Aurora borealis (Northern Lights) occur in ionosphere
Exosphere• 550km - no limit
above Earth’s surface• Satellites orbit Earth
in the exosphere– Phone signals– Television signals
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Review Questions
a. What significant role does the atmosphere have in providing us with water to drink?
b. Air is invisible, so how does it have density?
c. How does air pressure change as altitude increases? How does density change?
d. Which layer of the atmosphere is the most important to you? Justify you reasons.
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What is the Atmosphere?
It is the layer of gases that surround the earth.