2. UNIT THREE: Matter, Energy, and Earth  Chapter 8 Matter and Temperature  Chapter 9 Heat  Chapter 10 Properties of Matter  Chapter 11 Earth’s Atmosphere and Weather

4. Chapter Eleven: Earth’s Atmosphere and Weather  11.1 Earth’s Atmosphere  11.2 Weather Variables  11.3 Weather Patterns

5. Investigation 11A  Key Question: How does solar radiation affect the heating and cooling of continents and oceans? Heating Land and Water

6. 11.1 Learning Goals  Describe the composition of Earth’s atmosphere.  Explain the meaning of atmospheric pressure and describe how it is measured.  Identify the layers of Earth’s atmosphere and discuss unique characteristics of each layer.

7. 11.1 The Atmosphere  Earth’s atmosphere is a layer of gases surrounding the planet, protecting and sustaining life.  It insulates us so that we don’t freeze at night.  Its ozone layer protects us from the sun’s ultraviolet rays.  It also contains the carbon dioxide needed by plants for photosynthesis, and the oxygen we need to breathe.

8. 11.1 What's in Earth's atmosphere?  This wonderful protective layer exists around Earth because our planet has just the right balance of size and distance from the sun.  Nitrogen gas makes up about 78 percent of Earth’s atmosphere.  The second most abundant gas is oxygen, which makes up 21 percent of Earth’s atmosphere.

9. 11.1 Nitrogen Cycle  Nitrogen is important to protein which is found in the body tissues of all living things.  Nitrogen is cycled through the soil and into plants and finally when living things die and decay.

10. 11.1 Why is Earth different?  The atmospheres of Venus, Earth, and Mars were formed in similar ways, so we might expect them to contain similar elements. Photosynthesis changed Earth’s atmosphere.

11. Photosynthesis and the atmosphere  Photosynthesis converts carbon dioxide to oxygen in a process that allows living things use the sun’s energy.

12. 11.1 Earth stores carbon  Many marine organisms such as microscopic phytoplankton use carbon dioxide dissolved in seawater to form shells of calcium carbonate.

13. 11.1 Atmospheric pressure  Atmospheric pressure is a measurement of the force due to air molecules at a given altitude.  The pressure of the atmosphere decreases as you rise above sea level.

14. 11.1 Pressure changes with altitude

15. 11.1 Atmospheric pressure  At sea level, the weight of the column of air above a person is about 9,800 newtons (2,200 pounds)!  This is equal to the weight of a small car.  Why aren’t we crushed by this pressure?

16. 11.1 Measuring Pressure

17.  A barometer is an instrument that measures atmospheric pressure.  Long ago, mercury barometers were used.

18. 11.1 Parts of an Aneroid Barometer

19. 11.1 Layers of the Atmosphere  Four Layers  Thermosphere  Mesosphere  Stratosphere  Troposphere*

20. 11.1 Our Atmosphere  Troposphere: where we live  Stratosphere: contains the ozone layer  Mesosphere: where the temperature is coldest  Thermosphere, where the temperature is highest

21. Other layers  The ionosphere is part of the thermosphere and is where the Sun’s ultraviolet light creates charged atoms and molecules called ions.  The exosphere begins at about 500 kilometers above Earth’s surface and does not have a specific outer limit.