1. Chapter 15: The Atmosphere

2. Lesson 1: Earth’s Atmosphere

3. Properties of the Atmosphere
Properties of the atmosphere include its composition, relative humidity, temperature, and air pressure.
The atmosphere is the thin layer of gases that surrounds Earth.
We live at the bottom of the atmosphere, which provides us with oxygen, protects us from the most harmful rays in sunlight, and transports and recycles water.

4. Composition of the Atmosphere
The atmosphere consists of roughly 78% nitrogen gas and 21% oxygen gas.
Nitrogen gas occurs as a molecule with the chemical formula N2.
The most common form of oxygen in the atmosphere occurs as a molecule having the chemical formula O2.
During combustion, oxygen combines chemically with a fuel and produces carbon dioxide and water.
Air also contains water – solid, liquid, and gas – that has a chemical formula of H2O

5. In general, warm air can hold more water vapor than cooler air.
Relative Humidity
Relative humidity is the ratio of water vapor the air contains to the maximum amount it could have at that temperature.
In general, warm air can hold more water vapor than cooler air.
Water vapor becomes liquid water or ice through the process of condensation
Dew, frost, and clouds are the result of condensation
During the formation of clouds, water vapor condenses on tiny particles in the air such as salt crystals, smoke and dust.

6. Air temperature varies from place to place, and from time to time.
The sun’s rays strike some areas more directly than others

7. A barometer is an instrument that measures air pressure
Air pressure, or atmospheric pressure, is the force exerted by air on the area below it.
A barometer is an instrument that measures air pressure
In a mercury barometer air pressure pushes a column of mercury upward in a tube
An aneroid barometer has a metal chamber whose walls bend inward when air pressure is high and bend outward when air pressure is low.
In general, the lower the altitude the higher the air pressure

8. Layers of the Atmosphere
The main layers of the atmosphere are the troposphere, stratosphere, mesosphere, and thermosphere.

9. The troposphere
The lowest layer of the atmosphere, directly above the ground
Contains the oxygen we need to live
The movement of air within the troposphere is largely responsible for Earth’s weather.
Almost all clouds are found here
Contains three quarters of the atmosphere’s mass
Averages about 11 kilometers in height
The higher the air is above Earth, the cooler it becomes
A layer at the top acts like a cap

10. Layer of the atmosphere above the troposphere
The stratosphere
Layer of the atmosphere above the troposphere
Extends kilometers above sea level
Gases do not mix much
The highest part is warmer than the lower levels
Ozone is concentrated in a portion of the stratosphere called the ozone layer.
Ozone gas absorbs and scatters the sun’s UV rays
Protects organisms from harmful UV rays
A pollutant if present in the troposphere

11. The mesosphere
Layer above the stratosphere
Extends kilometers above sea level
Temperatures decrease with altitude
Air pressure is extremely low

12. The thermosphere
The top layer
Begins about 80 kilometers above Earth’s surface and extends upward into space.
Air is very thin
Temperature is very high
Disturbances produce the northern lights

13. The Troposphere and Weather
Processes that affect weather in the troposphere include heat transfer and the interaction of air masses.
Weather refers to atmospheric conditions over short time periods, typically hours or days, and within relatively small areas.
Climate describes the pattern of atmospheric conditions in large geographic regions over long periods.
Energy from the sun heats the atmosphere.

14. Radiation is the transfer of energy through space
Heat travels from the sun to Earth’s atmosphere by radiation
No direct contact between the heat source and the object being heated

15. Conduction is the transfer of heat directly between two objects that are in contact with one another.
Occurs when molecules collide and energy is transferred from one molecule to another
Occurs between Earth’s surface and the molecules in the air

16. Sinking cool air and rising warm air form convection currents.
Convection is the transfer of heat by the movement of currents within a fluid.
Cooler air is denser than warmer air and sinks to the surface of Earth where it picks up heat and begins to rise.
Sinking cool air and rising warm air form convection currents.
Cause winds and move heat through the troposphere

17. A large body of air is called an air mass
Properties such as temperature, pressure, and humidity are similar throughout

18. The boundary between air masses that differ in temperature and moisture is called a front.
A warm front is a boundary along which a mass of warmer, moister air pushes against a mass of cooler, drier air.
Warm air rises above the cool air mass and then cools
Can result in clouds and light rain

19. A cold front is the boundary along which a colder, drier air mass pushes against a warmer, moister air mass.
Cold air tends to wedge beneath the warmer air
May result in clouds, heavy precipitation, and sudden weather changes

20. Lesson 2: Pollution of the Atmosphere

21. Sources of Air Pollution
Air pollution can be caused by natural processes and human activities
Air pollution is the release of damaging materials into the atmosphere
The substances that are released are called emissions
Dust storms, volcanic eruptions, and forest fires are examples of natural processes that produce air pollution.

22. Air pollution can come from point sources or nonpoint sources.
Most air pollution comes, directly or indirectly, from the combustion of fossil fuels.
Fossil fuels are carbon-containing fuels that formed from the remains of living things.

23. Primary air pollutants are pollutants released directly into the troposphere
Ex: soot and carbon monoxide
Secondary air pollutants are pollutants produced when primary air pollutants react chemically with other substances
Ex: tropospheric ozone and sulfuric acid

24. How Air Pollutants Affect Your Health
Air pollutants can damage the respiratory system, interfere with the body’s uptake of oxygen, and cause cancer
Air pollutants irritate people’s air passages and lungs
Asthma, bronchitis, and emphysema have all been linked to air pollutants
Carbon monoxide interferes with your body’s ability to deliver oxygen to cells
Can cause headaches, tiredness, nausea, heart damage, and can be fatal.
Trace amounts of some air pollutants, such as soot and benzene, may contribute to cancer.

25. Smog and Temperature Inversions
Temperature inversions may trap smog close to the surface of Earth, preventing the pollutants from dispersing.
Smog is an unhealthy mixture of air pollutants that may form over cities and nearby areas.

26. Industrial Smog
Produced when soot combines with sulfur compounds and water droplets in air
Government regulations have decreased this type of smog in developed nations

27. Main source is the exhaust of cars and trucks
Photochemical Smog
A thick, brownish haze that forms when sunlight acts on certain air pollutants, such as nitrogen oxides and hydrocarbons
Tropospheric ozone is the most abundant pollutant in photochemical smog
Can damage living tissue
Main source is the exhaust of cars and trucks

28. Temperature Inversions
In the troposphere, air temperature usually decreases as altitude increases.
A temperature inversion, or thermal inversion, is the condition in the troposphere in which a layer of cooler air is located beneath a layer of warmer air
Since cold air has a greater density, the air at Earth’s surface does not rise and mix with the air higher up.
Keeps air pollutants from going away

29. Acid Deposition
Acid deposition results when products of combustion combine with water, oxygen, and other substances in the atmosphere.
Water vapor containing acids that falls to the ground as rain, snow, sleet or hail is called acid deposition.
Normal precipitation is slightly acidic (pH 5.6) and acid precipitation has a lower pH
Main sources include sulfur dioxide and nitrogen oxides that are produced through the burning of fossil fuels
Can harm ecosystems and structures that humans have built

30. Possible effects:
Lowering the pH of a lake
Killing trees
Releasing harmful chemicals in the soil
Erode stone surfaces
Increase acidity of drinking water

31. Lesson 3: Controlling Air Pollution

32. The Clean Air Act
The Clean Air Act has provisions that have reduced air pollution in the United States.
First passed in 1963 and then revised in 1970 and 1990
Goal is to protect and improve the quality of air in order to safeguard human health and the environment

33. Limits emissions of pollutants by motor vehicles and industries
Provisions:
Limits emissions of pollutants by motor vehicles and industries
Sets standards for air quality
Limits the concentration of specific air pollutants
Lets people sue industries that break the rules
Sets aside funds for research into pollution control

34. Reduction in Air Pollutants Cars and trucks now cause less pollution
The EPA sets nationwide standards governing air pollutants and air quality
Reduction in Air Pollutants
Cars and trucks now cause less pollution
A catalytic converter is a device in a motor vehicle that reduces the amount of air pollutants in emissions
Today, gasoline contains almost no lead
Industries and power plants use scrubbers
A scrubber removes pollutants or changes them chemically before they leave factory smokestacks.

35. Ozone: A Success Story
Nations have taken steps to deal with the problem of ozone loss in the stratosphere.
The term ozone hole refers to the area of lowered ozone concentration over Antarctica that occurs every year from August until October.
By 1985, the level of ozone was 40-60% lower than it had been 10 years before

36. In 1974, scientists Sherwood Rowland and Mario Molina suggested that chlorofluorocarbons could cause ozone depletion.
Chlorofluorocarbons (CFCs) are a family of chemical compounds containing chlorine, fluorine, and carbon
Manufactured in large amounts and used in refrigerators and aerosol spray cans.
CFCs were rising into the stratosphere and then releasing chlorine atoms that react with ozone, destroying the ozone molecules.

37. The Montreal Protocol is a treaty that limits the production of chlorofluorocarbons signed in 1987 by multiple nations.
Evidence indicates that the ozone layer is beginning to recover – in the last few years the concentrations of stratospheric ozone have stabilized.