The Atmosphere • The Air Around You • Air Quality • Air Pressure • Layers of the Atmosphere
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.
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.
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?
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.
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.
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?
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.
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.
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.
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?
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.
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.
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) Layers of the Atmosphere
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.
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.
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?