1. Composition of the Atmosphere

2. Weather
Weather- the condition of Earth’s atmosphere at a particular time and place
Atmosphere- the later of gases that surround the planet

3. The atmosphere makes conditions suitable for living things
It contains oxygen and other gases living things need to live
It keeps Earth’s surface warm enough for water to exist as a liquid
Protects living things from radiation from the sun
Prevents the surface from being hit by most meteoroids

4. Composition of the Atmosphere

5. Nitrogen Most abundant gas in the atmosphere
Is essential to living things
Is found in proteins
Is needed for growth and repair of cells
Most living things cannot obtain nitrogen directly from the air

6. Oxygen Second most abundant gas in the atmosphere
Plants and animals take it directly from the air
Is needed to release energy from food
Is needed for fuels to burn
It forms ozone when it interacts with lightning

7. Carbon Dioxide Is essential to life
Plants must have Carbon Dioxide to produce food
Animals give carbon dioxide off as a waste product
Burning fuels release carbon dioxide

8. Other Gases Oxygen and nitrogen make up 99% of dry air
Carbon Dioxide and argon make up most of the other 1%
The remaining gases are called trace gases because only small amounts of them are present

9. Water Vapor In reality, air is not dry because it contains water vapor
Water vapor- water in the form of a gas
It is invisible and is not the same as steam

10. Water Vapor Cont.
The amount of water vapor in the air varies from place to place
It plays an important role in the weather
Clouds form when water vapor condenses out of the air to form tiny droplets of liquid water or crystals of ice. The droplets or crystals fall as rain or snow if they become large enough.

11. Particles
Air contains tiny solid and liquid particles of dust, smoke, salt, and other chemicals