1. Composition of the Atmosphere 3/2/15 15-1a pgs. 392-394 IN: What is air made of?

2. TERMS TO LEARN & OBJECTIVES TERMS: ATMOSPHERE AIR PRESSURE ALTITUDE OBJECTIVES: Discuss the composition of the Earth’s atmosphere. Explain why pressure changes with altitude. Explain how temperature changes with altitude.

3. What is an atmosphere? Atmosphere – a mixture of gases that surrounds a planet, such as Earth.

4. Composition of the Atmosphere Contains mostly Nitrogen and Oxygen. Besides gas the atmosphere also contains small amounts of solids and liquids.

5. Atmospheric Pressure The Earth’s atmosphere is held around the planet by gravity. Gravity pulls that gas molecules in the atmosphere toward the Earth’s surface, giving them weight.

6. Atmospheric Pressure As you move farther away from the Earth’s surface, air pressure decreases because fewer gas molecules are pushing on you.

7. Like the bottom row of the human pyramid, the lower atmosphere experience greater pressure than the upper atmosphere.

8. Atmospheric Pressure Altitude – the height of an object above the Earth’s surface.

9. Atmospheric Pressure As altitude increases, air pressure decreases.

10. Air Temperature Air temperature also changes as you increase altitude. As you pass through the atmosphere, air temperature changes between warmer and colder conditions.

11. Air Temperature The temperature differences result mainly from the way solar energy is absorbed as it moves downward through the atmosphere. Some parts of the atmosphere are warmer because they contain gases that absorb solar energy.

12. Air Temperature As altitude increases, air temperature varies from hot to cold.

13. Air Temperature

14. Atmospheric Pressure and Temperature

15. OUT: Explain why pressure decreases but temperature varies as altitude increases.