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Science
8th Grade
Chapter 15
Section 1 The Air Around You
Key Terms
Weather- the condition of Earth’s atmosphere at a particular time and place
Atmosphere- the envelope of gases that surrounds the planet
Ozone- a form of oxygen with three oxygen atoms
Water vapor- water in the form of gas
Key Concepts
Four most common gases in dry air
1. Nitrogen makes up about ¾ of the air
2. Oxygen makes up ¼ of the air
3. carbon dioxide
4. argon
Ways that the atmosphere is important to life on Earth
1. contains oxygen and other gases that we need to survive
2. traps the heat from the sun in to keep the water in liquid form
3. protects us from the radiation from the sun
4. prevents Earth’s surface from being hit by rocks, or meteoroids
Section 2 Air Pressure
Key Terms
Density-the amount of mass in a given volume of air
Density=Mass/Volume
Pressure- the force pushing on an area or surface
Air pressure- result of the weight of the column of air pushing down on an area
Barometer- instrument used to measure air pressure
Mercury barometer- a glass tube at the bottom end and filled with mercury
Aneroid barometer- airtight metal chamber that is sensitive to changes in air
pressure
Altitude- elevation or the distance above sea level
Key Concepts
Air pressure decreases as altitude increases. As air pressure decreases so does density.
Air pressure is greatest at sea level.
Density affects air pressure by the denser a substance is the more mass per unit of volume
than a less dense substance. Denser air exerts more pressure than a less dense air.
The instruments that measure air pressure are the Mercury barometer and the aneroid
barometer. Units to measure air pressure are in millibars or inches of mercury.
1 inch of mercury =33.87 millibars.
Example: 30inches of mercury x 33.87= 1016 millibars.
The reason it is hard to breathe at the top of a mountain is because the density of air
decreases and there are fewer oxygen molecules to breathe in each cubic meter of air than
at sea level.
Section 3 Layers of the Atmosphere
See copy
Section 4 Air Quality
Key Terms
Pollutants- harmful substances in the air, water, or soil
Examples of pollutants from burning fossil fuels are carbon monoxide, nitrogen
dioxide, sulfur oxides. Other pollutants are farming, forest fires and construction.
Half of the pollution comes from cars and other motor vehicles.
Photochemical Smog- the brown haze in sunny cities
Main pollutant in smog is hydrocarbons and nitrogen oxides because they react to
form a brownish mixture of ozone and other pollutants.
Causes health problems like irritation of the eyes throat and lungs (asthma),
respiratory illness and lung damage
Acid Rain- rain that contains more acid than normal
Can damage surfaces of buildings and harm lakes and ponds killing the life there.
The human activity responsible for the formation of smog and acid rain is the
burning of fossil fuels.
The Environmental Protection Agency (EPA) monitors air pollutants in the US.
Ways we could reduce air pollution would be to
1. Use public transportation more
2. Stricter regulations
Pollution has decreased over the last 30 years due to better technology so that burning
fossil fuels do not release as much pollutants into the air and cars have become better
designed also.