3. The Junk in the Air Ain’t cake but it comes in layers Name that gasProperties of Air 100 200 400 300 400 300 200 400 200 100 500 100

4. Photochemical smog is created by the action of this on chemicals. What is sunlight? Category 1 Question 1

5. Harmful substances in the air, water, or soil are called this. What are pollutants? Category 1 Question 2

6. Particles of carbon that enter the air when wood or coal is burned are called this. What is soot? Category 1 Question 3

7. Acid rain is caused by the burning of coal that contains a lot of this. What is sulfur? Category 1 Question 4

8. True or False? Over the past 30 years, air quality in the United States has improved. If false, what word makes it true? True Category 1 Question 5

9. The warmest layer of the atmosphere. What is the thermosphere? Category 2 Question 1

10. The layer of the atmosphere that reflects radio waves. What is the ionosphere? Category 2 Question 2

11. The stratosphere helps protect Earth from too much sun because it contains this. What is ozone? Category 2 Question 3

12. The four main layers of the atmosphere are classified according to changes in this. What is temperature? Category 2 Question 4

13. True or False? The aurora borealis occurs in the ionosphere. If false, what makes it true? True Category 2 Question 5

14. The percentage of oxygen in the atmosphere. What is 21 percent? Category 3 Question 1

15. A gas in the atmosphere that varies between zero and four percent in different places. What is water vapor? Category 3 Question 2

16. Is the most abundant gas in the atmosphere. What is nitrogen? Category 3 Question 3

17. True or false? Fires need nitrogen to burn. If false, what word makes it true? False, oxygen. Category 3 Question 4

18. True or false? Altitude is the condition of Earth’s atmosphere at a particular time and place. If false, what word makes it true? What is weather? Category 3 Question 5

19. The amount of mass in a given volume of a substance. What is density? Category 4 Question 1

20. As the density of air decreases, its pressure… What is decreases? Category 4 Question 2

21. Air pressure is measured in this type of unit. What is in millibars? Category 4 Question 3

22. The force pressing on an area or surface. What is pressure? Category 4 Question 4

23. Category 4 Question 5 Air pressure decreases as altitude does this. What is increases?