1. Chapter 15 Section 7 What causes air pollution?
Objectives:
Identify causes of air pollution.
Explain how air pollution harms the environment.

2. Air Pollution
The burning of fossil fuels is the major cause of air pollution.
When these fuels are burned, harmful substances enter the atmosphere.
Thick, black smoke from chimneys contains dust and soot.

3. Air Pollution
Dust and soot are pollutants that can remain in the air for a long time.
They can irritate eyes, throat, and lungs.
Many cities have a smog problem.
Smog is a mixture of smoke, fog, and chemicals.
Smog also irritates the lungs of people, especially those with breathing problems.

4. IDENTIFY:
What is the major cause of air pollution?

5. Acid Rain Cars and factories burn fossil fuels.
This releases large amounts of carbon dioxide and other gases into the air.
Some of these gases mix with water in the air and form acids.
The acids then fall to Earth as acid rain.
Acid rain is harmful to both living and nonliving things.

6. Acid Rain Acid rain that falls into lakes and streams kills fish.
Acid rain also harms trees and causes brick, stone, and metal structures to weather, or break apart.

7. 2. EXPLAIN:
How does acid rain form?

8. Temperature Inversions
Some large cities are ringed by mountains.
As air flows into a valley, it pushes the warm air upward.
This warm air becomes caught between two layers of cold air.
The warm air cannot rise further because of the cooler air pushing down on it.
The mountains block the warm air from leaving the area.
This potentially dangerous condition is known as a temperature inversion.

9. Temperature Inversions
During temperature inversion, smog will continue to build up until a new weather system pushes the warm air up over the mountains.
The cooler air below can then circulate, reducing pollution.

10. 3. DESCRIBE:
What is a temperature inversion?

11. Carbon Dioxide Levels Fuels need oxygen to burn.
When fossil fuels burn, they give off the gas carbon dioxide.
The carbon dioxide traps heat energy produced by the Sun’s rays.
This is called the greenhouse effect.
Carbon dioxide is a greenhouse gas.

12. Carbon Dioxide Levels
Some scientists think that the increase of carbon dioxide in the air is causing the average air temperature to rise around the world.
This rising temperature may cause dramatic climate changes.

13. 4. RELATE:
How can an increase of carbon dioxide in the air cause air temperature to rise?

14. Protecting the Air
Many countries have laws to help control or reduce air pollution.
In the United States, most vehicles must have anti- pollution devices.
Factories, too, must have filters on their smokestacks.
The filters reduce the number of solid particles, called particulates, released into the air.
However, using less fuel is the best way to reduce air pollution.

15. 5. EXPLAIN:
How do laws help reduce air pollution?

16. 15-7 Classwork CHECKING CONCEPTS
Smoke contains tiny pieces of dust and ___.
Smog is a mixture of smoke, fog, and ___.
Carbon dioxide traps ___ energy.
Some pollution gases combine with ___ in the air to form acid rain.

17. 15-7 Classwork THINKING CRITICALLY
5. PREDICT: The rising heat in Earth’s atmosphere could cause glaciers to melt. How would this affect sea level and coastal cities?
6. HYPOTHESIZE: Is acid rain more of a problem in wet or dry climates? Explain.
7. INFER: What two words form the word smog?