| A | B |
|---|
| weather | The condition of Earth's atmosphere at a particular time and place |
| atmosphere | The layer of gases that surrounds the planet |
| water vapor | Water in the form of a gas |
| pollutants | Harmful substances in the air, water or soil |
| photochemical smog | The brown haze that forms in cities |
| acid rain | rain that contains more acid than normal |
| density | The amount of mass in a given volume of air |
| pressure | The force pushing on an area or surface |
| air pressure | The result of the weight of a column of air pushing down on an area |
| barometer | An instrument that is used to measure changes in air pressure |
| altitude | Elevation above sea level |
| troposphere | The lowest layer of Earth's atmosphere, where weather occurs |
| stratosphere | The second lowest layer of Earth's atmosphere |
| mesosphere | The middle layer of Earth's atmosphere, where most meteoroids burn up |
| thermosphere | The outermost layer of Earth's atmosphere |
| ionosphere | The lower part of the thermosphere |
| exosphere | The outer layer of the thermosphere extending outward into space |
