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is the condition of the Earth's atmosphere at a particular time and place


is the average condition of the Earth's atmosphere at a place


is the layer of gases that surrounds the planet. Earth's atmosphere is made of about 78% nitrogen, 21%oxygen, and other gases


is a form of oxygen that has three oxygen atoms instead of the usual two

water vapor

water in the form of a gas


harmful substances in the air, water, or soil. Air pollution is caused by pollutants in the air. Most air pollution is caused by the burning of fossil fuels such as coal, oil, and gasoline.

photochemical smog

the brown haze caused by the action of sunlight on chemicalpollutants

acid rain

rain that contains more acid than normal and forms when nitrogen oxides and sulfur oxides combine with water in the air.


the combination of gases, mostly nitrogen and oxygen, that make up the atmosphere. Air has certain properties: mass, density, pressure


the force pushing on an area or surface

air pressure

is the result of the weight of a column of air pushing down on an area


weather instrument used to measure air pressure

mercury barometer

an instrument consisting of a glass tube open at the bottom and partially filled with mercury used to measure air pressure

aneroid barometer

an instrument that has an airtight metal chamber that expands and contracts depending upon the air pressure


elevation, the distance above sea level

layers of the atmosphere

the layers of the atmosphere are categorized by changes in temperature.


lowest layer of the Earth's atmosphere, where most weather occurs, "tropo"means changing, 9-16 km thick.


second layer of the Earth's atmosphere, upper stratosphere has a layer of ozone, extends from top of troposphere to about 50 km.


third layer of the Earth's atmosphere, "meso" means middle, outermesosphere is the coldest part of the atmosphere, begins at 50 km and ends at 90 km.


upper most layer of the Earth's atmosphere, "thermo" means heat, dividedinto two layers- ionosphere and exosphere, air is very thin and very hot.


lower layer of the thermosphere, runs from 80 km to 550 km


upper layer of the thermosphere, "exo" means outer, runs from 550 km forthousands of kilometers until the atmosphere fades into deep space.

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