Weather—The Atmosphere Weather is the condition of Earth’s atmosphere at a particular time and place. Weather is the condition of Earth’s atmosphere at a particular time and place. The atmosphere is the layer of gases that surround the planet. The atmosphere is the layer of gases that surround the planet. The atmosphere is very thin. The atmosphere is very thin.

Earth’s atmosphere has conditions perfect for living things. Oxygen Water Warmth Protection from UV light

Composition of Atmosphere Nitrogen 78% Nitrogen 78% Oxygen 21% Oxygen 21% Carbon dioxide Carbon dioxide Water vapor Water vapor (argon, neon, (argon, neon, methane, krypton, hydrogen)

The Gases -- Nitrogen Most abundant = N 2 Most abundant = N 2 Living things need nitrogen but we can’t get it from the air Living things need nitrogen but we can’t get it from the air Bacteria in the soil convert nitrogen gas into useable nitrogen for plants Bacteria in the soil convert nitrogen gas into useable nitrogen for plants Animals eat plants (or animals that eat plants) to get their nitrogen Animals eat plants (or animals that eat plants) to get their nitrogen

The Gases -- Oxygen Most organisms use O 2 or oxygen gas to burn their food Most organisms use O 2 or oxygen gas to burn their food Anything that burns uses oxygen gas Anything that burns uses oxygen gas Ozone is O 3 Ozone is O 3

Carbon Dioxide CO 2 CO 2 Small amount of the atmosphere but necessary for plants who use it to make their food Small amount of the atmosphere but necessary for plants who use it to make their food May cause global warming May cause global warming

Water Vapor Clouds Clouds Water in the form of a gas Water in the form of a gas

Solid Particles Air contains tiny solid particles of Air contains tiny solid particles of Dust Dust Smoke Smoke Salt Salt Chemicals Chemicals

Air Quality Air Pollution Air Pollution Harmful substances in the air Harmful substances in the air Most are from the burning of fossil fuels Most are from the burning of fossil fuels Coal Coal Oil Oil Gasoline Gasoline Diesel fuel Diesel fuel Natural gas Natural gas

Particles Natural sources Natural sources Volcanoes Volcanoes Ocean waves Ocean waves Forest fires Forest fires Dust storms Dust storms Plants Plants Human Activities Human Activities Farming Farming Construction Construction Factories Factories Cars Cars Making electricity Making electricity

SMOG Photochemical smog Photochemical smog Sunlight + chemicals Sunlight + chemicals Includes ozone Includes ozone Los Angeles-type smog Los Angeles-type smog

Improving Air Quality What are your ideas to help make the air cleaner? What are your ideas to help make the air cleaner? It will be your job… It will be your job…

Air Pressure —The force pushing on an area or surface Air has mass Air has mass Air has volume Air has volume Therefore, air has density Therefore, air has density More molecules per volume means a greater density More molecules per volume means a greater density The higher the density, the higher the air pressure The higher the density, the higher the air pressure

Air Pressure is caused by the weight of a column of air pushing down on an area Air Pressure is caused by the weight of a column of air pushing down on an area 14 pounds per square inch 14 pounds per square inch Why don’t you feel the weight? Why don’t you feel the weight?

Measuring Air Pressure A barometer is an instrument used to measure air pressure. A barometer is an instrument used to measure air pressure. Mercury barometer is a glass tube partially filled with mercury that is open at the bottom in a dish of mercury. Mercury barometer is a glass tube partially filled with mercury that is open at the bottom in a dish of mercury.

The air pressure pushing down on the mercury is equal to the weight of the mercury in the tube. The air pressure pushing down on the mercury is equal to the weight of the mercury in the tube. The mercury in the tube is pushed up by increasing air pressure. The mercury in the tube is pushed up by increasing air pressure.

Aneroid Barometer The metal chamber is sensitive to changes in air pressure. The metal chamber is sensitive to changes in air pressure. It has thin metal walls that push in when air pressure is high and push out when air pressure is low. It has thin metal walls that push in when air pressure is high and push out when air pressure is low.

Units of Air Pressure Air pressure is measured in two main ways Air pressure is measured in two main ways Inches of mercury Inches of mercury Millibars – one inch = millibars Millibars – one inch = millibars

How Altitude Affects Air Pressure Air pressure decreases as altitude increases. Air pressure decreases as altitude increases. Air at sea level has the most air pressure because all the air above it is pushing down on it. Air at sea level has the most air pressure because all the air above it is pushing down on it.

Altitude Affects Density Why is it hard to do heavy exercise when you are in a high altitude? Why is it hard to do heavy exercise when you are in a high altitude? As you go up in altitude, the air is less dense. There are fewer molecules of oxygen per breath! As you go up in altitude, the air is less dense. There are fewer molecules of oxygen per breath!

Quiz 1. What is the most abundant gas in the atmosphere? 2. What causes most pollution? 3. What does a barometer measure? 4. Layers of the atmosphere are classified by what factor? 5. The weather layer of the atmosphere is called what?

6. What gas do plants use to do photosynthesis? 7. What gas is produced when things are burned? 8. When the mass of air increases, does it become MORE or LESS dense? 9. As altitude increases, does the air pressure INCREASE or DECREASE? 10. Which layer of the atmosphere has the ozone layer?

11. Which layer of the atmosphere has the highest temperature? 12. What instrument is used to measure air pressure without a liquid? 13. What is a natural source of solid particles in the air? 14. Name a human made particle in the air. 15. Why is carbon dioxide an important gas even though there isn’t much of it in the atmosphere?