1. The Atmosphere
Essential Question: What is the significance of the atmosphere to the existence of life on earth? pp

2. The Atmosphere
The atmosphere is the layer of gases and other particles that surround earth much like the peel of an apple covers it.

3. 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

4. Properties of Air in the Atmosphere
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
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

5. Composition of the Atmosphere
Nitrogen 78%
Oxygen 21%
All other gases 1%
Tiny solid and liquid particles of:
dust
smoke
salt
chemicals

6. Structure of the Atmosphere
Troposphere
Stratosphere
Mesosphere
Thermosphere
Ionosphere
exosphere

7. 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

8. 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

9. 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)

10. Thermosphere Everything 80km above Earth’s surface Temp up to 1,800oC
Air very thin
Includes the ionosphere and exosphere

11. 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

12. Review Questions Air is invisible, so how does it have density?
What significant role does the atmosphere have in providing us with water to drink?
Air is invisible, so how does it have density?
How does air pressure change as altitude increases? How does density change?
Which layer of the atmosphere is the most important to you? Justify you reasons.

13. It is the layer of gases that surround the earth.
What is the Atmosphere?
It is the layer of gases that surround the earth.