| A | B |
|---|
| weather | The condition of Earth‘s atmosphere at a particular time and place |
| atmosphere | The envelope of gases that surrounds Earth |
| ozone | A form of oxygen that has three oxygen atoms in each molecule instead of the usual two |
| water vapor | Water in the form of a gas |
| density | The amount of mass of a substance in a given volume |
| pressure | The amount of force pushing on an area |
| air pressure | The pressure caused by the weight of a column of air pushing down on an area |
| barometer | An instrument used to measure changes in air pressure |
| mercury barometer | An instrument that measures changes in air pressure, consisting of a glass tube partially filled with mercury, with its open end resting in a dish of mercury |
| aneroid barometer | An instrument that measures changes in air pressure without using a liquid |
| altitude | Elevation above sea level |
| troposphere | The lowest layer of Earth’s atmosphere |
| stratosphere | The second-lowest layer of Earth’s atmosphere |
| mesosphere | The layer of Earth’s atmosphere immediately above the stratosphere |
| thermosphere | The outermost layer of Earth’s atmosphere |
| ionosphere | The lower part of the thermosphere |
| exosphere | The outer layer of the thermosphere |
| pollutants | Harmful substances in air, water, or soil |
| photochemical smog | A brownish haze that is a mixture of ozone and other chemicals, formed when pollutants react with each other in the presence of sunlight |
| acid rain | Rain that contains more acid than normal |
