1. DO Now 1._____hottest layer of the atmosphere 2._____ second most abundant gas in the atmosphere 3._____layer of the atmosphere we live in 4._____ the trace gas that traps heat 5._____ absorbs ultraviolet radiation

2. Key Questions 1. What does the dense mean? 2. Where are molecules the most dense? 3.Why are molecules the most dense at sea level? 4.What is altitude? What is atmospheric pressure? 5.What is a barometer? 6.What is the the relationship between altitude, pressure, and density?

3. 1. Dense-how closely packed molecules are to one another

4. 2. Molecules are most dense at sea level

5. 3. Molecules are the most dense at sea level because all of the molecules above are pressing down.

6. 4. Altitude-measure of the distance an object is above sea level

7. 5. Atmospheric Pressure-measure of the force per unit area of air molecules in the atmosphere at a given altitude

8. 6. Barometer- instrument use to measure air pressure

9. 7. Low Altitude more dense higher pressure more oxygen High Altitude less dense lower pressure less oxygen

10. This false-colored image was acquired during the Clementine mission. It shows airglow of the upper atmosphere as a thin blue line. The bright spot toward the right of the image is an urban area..