1. Air Pressure
When air pressure increases, the liquid in a mercury barometer rises
An aneroid barometer does not use liquid
Air pressure is greater at what point B
Altitude is greater at what point A
Density of the air is greatest at point B

2. 6. Air pressure – the result of the weight of a column of air pushing down on an area 7. Barometer – any instrument that measures air pressure 8. Density – the amount of mass in a given volume of air 9. Mercury barometer – an instrument that measures air pressure using liquid mercury 10. Aneroid barometer – an instrument that measures air pressure without using a liquid 11. Altitude – the distance above sea level, elevation

3. Notes: Earth’s Atmosphere
A. Atmosphere – the dome of solids, liquids, and gases that surround the Earth
B. The atmosphere has many jobs:
1. absorbs energy from the sun
2. recycles water
3. works to provide a moderate climate
4. protects us from high energy radiation
5. protects us from the vacuum of space (a vacuum is a place with NO AIR)
C. Gases in the Atmosphere
1. Nitrogen (N) – the most abundant; makes up 78%
2. Oxygen (O) – second most abundant; makes up 21%
3. Other gases – making up 1% (Argon, Carbon Dioxide, Water vapor and other trace gases)

4. D. Solids and liquids in the atmosphere:
1. dust, salt and pollen
2. little droplets of liquid water other than what is in the clouds
E. Layers of the Atmosphere
1. Lower levels
a. Troposphere –
1. lowest layer
2. Earth’s weather occurs here
3. contains 90% of the gases that make up the atmosphere
4. extends to about 10km above Earth’s surface

5. b. Stratosphere –
1. from about 10km-50km above Earth’s surface
2. upper stratosphere is warmer because of the ozone layer
a. Ozone layer – layer of oxygen gas (O3)
b. Absorbs the ultraviolet radiation form the sun
c. energy is converted to heat and warms the air
2. Upper Layers of the Atmosphere
a. Mesosphere –
1. middle layer
2. outermost level in mesosphere is the coldest (-90C)
3. If you have seen a shooting star, you are seeing a meteor burn up in the mesosphere

6. b. Thermosphere –
1. 80km above Earth to outer space
2. no definite end to Earth’s atmosphere, the gas and air molecules are spread so far apart that they just blend into outer space
3. air is thin and very hot (1,800C) because energy from the sun hits this layer first
a. The Ionosphere –
1.) lowest layer of the thermosphere
2.) energy from the sun causes particles in the ionosphere to become electrically charged (ions)
3.) radio waves bounce off the charged particles and travel back to Earth
b. The Exosphere –
1.) “exo-“ means outer
2.) outer layer of the atmosphere
3.) satellites orbit in the exosphere