1. The Composition of the Earth’s Atmosphere

2. What’s in our Air? 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. 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. Nitrogen is the most abundant gas in the atmosphere. It makes up 78% of the Earth’s atmosphere. Each Nitrogen molecule consists of two nitrogen atoms. Nitrogen is the most abundant gas in the atmosphere. It makes up 78% of the Earth’s atmosphere. Each Nitrogen molecule consists of two nitrogen atoms.

3. What’s in the air? Oxygen makes up 21% of the gas in the atmosphere. Oxygen makes up 21% of the gas in the atmosphere. Oxygen is involved in important processes. Oxygen is involved in important processes. Most oxygen molecules have two oxygen atoms. Most oxygen molecules have two oxygen atoms. Ozone is a form of oxygen that has three oxygen atoms in each molecule instead of the usual two. Ozone is a form of oxygen that has three oxygen atoms in each molecule instead of the usual two. If you ever smelled a pungent smell in the air after a thunderstorm it’s the odor of the ozone. If you ever smelled a pungent smell in the air after a thunderstorm it’s the odor of the ozone.

4. What’s in the air? Carbon dioxide is essential to life. Plants must have CO2 to produce foods. Carbon dioxide is essential to life. Plants must have CO2 to produce foods. When fuels such as coal and gasoline are burned,they release carbon dioxide. When fuels such as coal and gasoline are burned,they release carbon dioxide. Burning these fuels increases the amount of carbon dioxide in the atmosphere. (This is not good) Burning these fuels increases the amount of carbon dioxide in the atmosphere. (This is not good)

5. What’s in the air? Oxygen and Nitrogen together make up 99% of dry air. Argon and CO2 make up most of the other 1%. Oxygen and Nitrogen together make up 99% of dry air. Argon and CO2 make up most of the other 1%. Water vapor is present in the form of gas. Water vapor is invisible. Water vapor is present in the form of gas. Water vapor is invisible. The amount of water vapor in the air varies greatly from place to place and from time to time. Water vapor plays an important in the Earth’s weather. The amount of water vapor in the air varies greatly from place to place and from time to time. Water vapor plays an important in the Earth’s weather. Clouds form when water vapor condenses out of the air to form tiny droplets of liquid water or crystals of ice. Clouds form when water vapor condenses out of the air to form tiny droplets of liquid water or crystals of ice.

6. What’s in the air? Air also contains tiny solid and liquid particles of dust, smoke, salt and other chemicals. Air also contains tiny solid and liquid particles of dust, smoke, salt and other chemicals. By trapping energy from the sun, the atmosphere keeps most of the Earth’s surface warm enough for water to exist as a liquid. Earth’s atmosphere protects us from dangerous radiation. By trapping energy from the sun, the atmosphere keeps most of the Earth’s surface warm enough for water to exist as a liquid. Earth’s atmosphere protects us from dangerous radiation.

7. Air pressure Because air has mass,it also has other properties,including density and pressure Because air has mass,it also has other properties,including density and pressure Density is the amount of mass in a given volume of air. Density= Mass Density is the amount of mass in a given volume of air. Density= Mass Volume Volume The force pushing on an area or surface is known as pressure. The force pushing on an area or surface is known as pressure. Air pressure is the result of the weight of a column of air pushing down on an area. The column of air extends upward through the entire atmosphere. Air pressure is the result of the weight of a column of air pushing down on an area. The column of air extends upward through the entire atmosphere. The air doesn’t crush you because the molecules in the air push in all directions-up, down and sideways. The air doesn’t crush you because the molecules in the air push in all directions-up, down and sideways. Air pressure can change from day to day. A denser substance has more mass per unit volume than less dense. Air pressure can change from day to day. A denser substance has more mass per unit volume than less dense. Barometer is an instrument that is used to measure air pressure. Two common barometers are mercury and aneroid barometers. Barometer is an instrument that is used to measure air pressure. Two common barometers are mercury and aneroid barometers.

8. Altitude Altitude or elevation is the distance above sea level. Altitude or elevation is the distance above sea level. Air pressure decreases as altitude increases. As air pressure decreases, so does density. Air pressure decreases as altitude increases. As air pressure decreases, so does density. Decreased pressure means gas molecules are farther apart at high altitude. Decreased pressure means gas molecules are farther apart at high altitude. Air at sea level has more gas molecules, more pressure. Air at sea level has more gas molecules, more pressure.

9. The Layers of the Atmosphere The atmosphere- the mixture of gases that surrounds Earth –extends from Earth’s surface to more than 6oo km into space. The atmosphere- the mixture of gases that surrounds Earth –extends from Earth’s surface to more than 6oo km into space. Both oxygen and carbon dioxide support life. Both oxygen and carbon dioxide support life. Certain bacteria change nitrogen from the atmosphere into substances plants can use to build proteins Certain bacteria change nitrogen from the atmosphere into substances plants can use to build proteins High in the atmosphere, a form of oxygen called ozone shields living things from much harmful radiation given by the sun. High in the atmosphere, a form of oxygen called ozone shields living things from much harmful radiation given by the sun.

10. Earth’s Atmosphere Earth’s atmosphere is not uniform; it’s properties change with altitude. The two properties that change with altitude are air temperature and pressure. Earth’s atmosphere is not uniform; it’s properties change with altitude. The two properties that change with altitude are air temperature and pressure.

11. Troposphere Layer nearest Earth Layer nearest Earth All weather happens here All weather happens here More than half of air in total atmosphere in this layer. More than half of air in total atmosphere in this layer. Temperatures drops as altitude increases. Temperatures drops as altitude increases.

12. Stratosphere Temperature goes up with altitude Temperature goes up with altitude Most jets fly here Most jets fly here Protective ozone layer at the top of the stratosphere. Protective ozone layer at the top of the stratosphere.

13. Mesosphere Temperatures drop with altitude; this is the coldest layer of the atmosphere. Temperatures drop with altitude; this is the coldest layer of the atmosphere. Meteors burn up this layer Meteors burn up this layer

14. Thermosphere Temperatures goes up with altitude; this is the hottest layer of the atmosphere Temperatures goes up with altitude; this is the hottest layer of the atmosphere Curtain of light called auroras occur in this layer. Curtain of light called auroras occur in this layer. Thermosphere is divided into two layers: Ionosphere and Exosphere Thermosphere is divided into two layers: Ionosphere and Exosphere Ionosphere is the lower layer in the thermosphere Ionosphere is the lower layer in the thermosphere

15. Ionosphere Energy from the sun causes gas molecules in the ionosphere to become electrically charged particles called ions. Radio waves bounce off ions in the ionosphere back to the Earth’s surface Energy from the sun causes gas molecules in the ionosphere to become electrically charged particles called ions. Radio waves bounce off ions in the ionosphere back to the Earth’s surface

16. Exosphere Outermost layer of the atmosphere Outermost layer of the atmosphere Temperatures goes up with altitude Temperatures goes up with altitude Satellites orbit in this layer. Satellites orbit in this layer.

17. Air Quality Some air pollution occurs naturally. But many types of the air pollution are the results of human activity. Some air pollution occurs naturally. But many types of the air pollution are the results of human activity. Natural sources- Forest Fires,soil erosion and dust storms. Natural sources- Forest Fires,soil erosion and dust storms. Human Activity: Farming, construction and burning of fossil fuels. Human Activity: Farming, construction and burning of fossil fuels. In the US, the federal and state governments have passed a number of laws to reduce air pollution. In the US, the federal and state governments have passed a number of laws to reduce air pollution.