2. What is Air? Air is the mixture of many gases that surround Earth The layer of air surrounding Earth makes up Earth’s atmosphere Air can be compressed (pushed into a smaller space) Air has mass and takes up space Air is made of particles too small to see

3. What Gases are in Air? Permanent Gases of the Atmosphere Nitrogen (N)78.08% Oxygen (O)20.95% Argon (Ar)0.93% Neon (Ne)0.002% Helium (He)0.0005% Krypton (Kr)0.0001% Hydrogen (H)0.00005% Xenon (Xe)0.000009% Variable Gases of the Atmosphere Water vapor (H₂O)0-4% Carbon dioxide (CO₂)0.039% Methane (CH₄)0.00017% Ozone (O₃)0.000004%

4. How Deep is Earth’s Atmosphere? 560-600 Km 85-560 Km 50-85 Km 0-20 Km 15-50 Km Least Dense Most Dense

5. The Troposphere The layer we live in is called the troposphere The depth of the troposphere depends on the temperature of the air, but it is the shallowest layer Air in the troposphere is warmest near the ground Weather happens in the troposphere This is the layer with the most air particles and air pressure

6. The Stratosphere A fast flowing stream of air, called the jet stream travels (west to east) between the troposphere and stratosphere The stratosphere has a layer of ozone (O₃) that protects us from UV radiation from the sun Air in the stratosphere is warmest near the top

7. The Mesosphere The mesosphere is colder than the Stratosphere (-90°C) This is the layer where meteors called shooting stars burn up while entering Earth’s atmosphere.

8. The Thermosphere The thermosphere has very little air The temperature in the thermosphere can change dramatically, but it is considered the hottest layer (1,500°C or higher!) The International Space Station is in the thermosphere

9. The Exosphere The exosphere is the layer that fades into space The temperature in the exosphere is low (-270°C) https://www.brainpop.com/science/earthsystem/earthsatmosphere/

10. What is Weather? Weather is the condition of the air in an area Conditions can change so they are called weather variables Scientists who study weather are called meteorologists Meteorologists use tools to measure the variables that changes in weather

11. Tools of Meteorology VariableTool Used TemperatureThermometer Air Pressure (density)Barometer Humidity (water vapor)Hygrometer Wind SpeedAnemometer Wind DirectionWind Vane anemometer wind vane hygrometer * Changes in pressure mean changes in weather. Falling pressure means rain is coming. Rising pressure means dry weather is coming.