| A | B |
|---|
| weather | the condition of Earth's atmosphere at a particular time and place |
| atmosphere | the envelpoe 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 gas |
| density | the amount of mass of a substance in a given volume; mass per unit volume |
| pressure | the force exerted on a surface divided by the total area over which the force is exerted |
| 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 measure 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 air pressure without using 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 |
| pollutant | A harmful substance substance in the air, water or soil |
| photochemical smog | a brownish haze that is a mixture of ozone and ohter chemicals, formed when pollutants react with each other in the presence of sunlight |
| acid rain | rain that contains more acid than normal |
