1. The Atmosphere

2.  The Air Around You  Air Quality  Air Pressure  Layers of the Atmosphere

3. The Air Around You - Vocabulary  Weather – The condition of Earth’s atmosphere at a particular time and place.  Atmosphere – The layer 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.

4. The Air Around You – Main Ideas  Earth’s atmosphere makes conditions on Earth suitable for living things.  Earth’s atmosphere is made up of nitrogen, oxygen, carbon dioxide, water vapor, and many other gases, as well as particles of liquids and solids.

5. The Air Around You – Guiding Questions  Describe two ways in which the atmosphere is important to life on Earth.  What are the four most common gases in dry air?  Why are the amounts of gases in the atmosphere usually shown as percentages of dry air?

6. Air Quality - Vocabulary  Pollutants – Harmful substances in the air, water, or soil.  Photochemical smog – A brownish haze that is a mixture of ozone and other chemicals, formed when nitrogen oxides, hydrocarbons, and other pollutants react with each other in the presence of sunlight.  Acid rain – Rain that contains more acid than normal.

7. Air Quality – Main Ideas  Most air pollution is the result of burning fossil fuels such as coal, oil, gasoline, and diesel fuel.  Nitrogen oxides, hydrocarbons, and other air pollutants react with one another in the presence of sunlight to form a mix of ozone and other chemicals called photochemical smog  Acid rain forms when nitrogen oxides and sulfur oxides combine with water in the air to form nitric acid.

8. Air Quality – Guiding Questions  How is most air pollution produced?  Name two natural and two artificial sources of particles in the atmosphere.  How is photochemical smog formed? What kinds of harm does it cause?  What substances combine to form acid rain?

9. Air Pressure - Vocabulary  Density – The amount of mass of a substance to a given volume.  Pressure – The force pushing on an area or surface.  Air pressure – A force that is the result of the weight of a column of air pushing down on an area.  Barometer – An instrument used to measure changes in air pressure.

10. Air Pressure - Vocabulary  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. Air pressure pushing on the mercury in the dish forces the mercury in the tube higher.  Aneroid barometer – An instrument that measures changes in air pressure without using a liquid. Changes in the shape of an airtight metal box cause a needle on the barometer dial to move.  Altitude - Elevation above sea level.

11. Air Pressure  Properties of air include mass, density, and air pressure.  Air pressure is the result of the weight of a column of air pushing down on an area.  Air pressure is measured with mercury barometers and aneroid barometers.  Air pressure decreases as altitude increases. As air pressure decreases, so does density.

12. Air Pressure – Guiding Questions  How does increasing the density of a gas affect its pressure?  Describe how a mercury barometer measures air pressure.  Why is the air at the top of a mountain hard to breathe?

13. Layers of the Atmosphere - Vocabulary  Troposphere – The lowest layer of Earth’s atmosphere, where weather occurs.  Stratosphere – The second-lowest layer of Earth’s atmosphere; the ozone layer is located in the upper stratosphere.  Mesosphere – The middle layer of Earth’s atmosphere; the layer in which most meteoroids burn up.  Thermosphere – The outermost layer of Earth’s atmosphere.

14. Layers of the Atmosphere - Vocabulary  Ionosphere – The lower part of the thermosphere, where electrically charged particles called ions are found.  Aurora borealis – A colorful, glowing display in the sky caused when particles from the sun strike oxygen and nitrogen atoms in the ionosphere; also called the Northern Lights.  Exosphere – The outer layer of the thermosphere, extending outward into space.

15. Layers of the Atmosphere  The thermosphere is composed of the ionosphere (80-550 km) and the exosphere (above 550 km)  Mesosphere (50-80 km)  Stratosphere (12-50 km)  Troposphere (0-12 km)

16. Layers of the Atmosphere – Main Ideas  The four mail layers of the atmosphere are classified according to changes in temperature. These layers are the troposphere, the stratosphere, the mesosphere, and the thermosphere.  Rain, snow, storms, and most clouds occur in the troposphere.  Ozone in the stratosphere absorbs energy from the sun.

17. Layers of the Atmosphere – Main Ideas  Most meteoroids burn up in the mesosphere, producing meteor trails.  The aurora borealis occurs in the ionosphere.  Communications satellites orbit Earth in the exosphere.

18. Layers of the Atmosphere – Guiding Questions  Describe one characteristic of each of the four main layers of the atmosphere.  What is a shooting start? In which layer of the atmosphere would you see it?  What is the aurora borealis? In which layer of the atmosphere does it occur?