1. The atmosphere is the thin layer of gases that surrounds Earth.
2. Relative humidity is the ratio of water vapor the air contains to the
maximum amount it could have at that temperature.
3. Air pressure, or atmospheric pressure, is theforce exerted by air on the area below it.
4. The lowest layer of the atmosphere, the one directlyabove the ground, is called the troposphere.
5. The stratosphere is the layer of the atmosphereabove the troposphere
6. The most common form of oxygen is O2, but oxygenalso occurs as O3, which is a gas called ozone.
7. Ozone is concentrated ina portion of the stratosphere called the ozone layer.
8. Above the stratospherelies the mesosphere, the layer that extends 50–80 kilometers(31–50 miles) above sea level.
9. In the mesosphere, temperaturesdecrease with altitude, reaching their lowest point at the top.
10. The thermosphere is the top layer, which begins about 80 kilometers (50 miles) above Earth’s surface and extendsupward into space.
11. Radiation: which is the transfer of energy throughspace.
12. Conduction isthe transfer of heat directly between two objects that are in
contact with one another.
13. Convection is the transfer of heat by the movement of currents within a fluid.
14. Sinking cool air and rising warm airform convection currents.
15. Convection currents cause winds and moveheat through the troposphere.
16. Throughout a large body of air called anair mass, properties such as temperature, pressure, and humidity aresimilar.
17. The boundary between air masses that differ in temperatureand moisture is called a front.
18. Air pollution isthe release of damaging materials into the atmosphere. The substancesreleased are called emissions.
19. Fossil fuels are carbon-containing fuels that formed millionsof years ago from the remains of living things.
20. Primary airpollutants, such as soot and carbon monoxide, are pollutantsreleased directly into the troposphere.
21. Harmful productsproduced when primary air pollutants react chemically
with other substances are called secondary air pollutants.
22. Smogis an unhealthy mixture of air pollutants that may form over cities andnearby areas.
23. A temperature inversion, or thermal inversion, is the conditionin the troposphere in which a layer of cooler air is located beneath a layerof warmer air.
24. When some pollutants combine with water, oxygen, and other chemicalsin the atmosphere, they form compounds called acids. These acids maysettle to the surface of Earth as acid deposition.
25. The Clean Air Act protects and improvesthe quality of air in order to safeguard human health and the environment.
26. A catalytic converter is a devicein a motor vehicle that reduces the amount of air pollutants in emissions.
27. A scrubber removes pollutants or changes them chemically before theyleave factory smokestacks.
28. The ozone holeis the area of lowered ozone concentration overAntarctica that occurs every year from August until October
29. Chlorofluorocarbons (CFCs) are a family of chemical compoundscontaining chlorine, fluorine, and carbon.
30. Montreal Protocol:the treaty, strengthenedby later amendments, that called for major cuts in CFC manufacture.