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As we have seen, the ozone layer in the stratosphere is a vital layer of protection for the Earth. This layer that contains most of the atmosphere’s ozone is far above the air that we breathe every day, and even above the altitude where most airplanes fly. However, when ozone forms near the surface in the troposphere, where humans breathe, it is an air pollutant that can harm our lungs and the natural environment. This tropospheric ozone is the same molecule as in the stratosphere. However, in the troposphere, ozone forms in very different ways than in the stratosphere. We’ll learn more about tropospheric ozone and other air pollutants in Lesson Five.

Additional resources

More information about good and bad ozone can be found at http://www.epa.gov/airnow/gooduphigh - a booklet by the EPA called Good Up High, Bad Nearby. Other great resources regarding ozone can be found at:

  1. http://www.epa.gov/ozone/strathome.html.
  2. http://www.windows.ucar.edu/tour/link=/Earth/Atmosphere/ozone_overview.html&edu=mid
  3. http://www.clean-air-kids.org.uk/ozonehole.html
  4. Comic strip from US EPA illustrating the two types of ozone: http://www.epa.gov/ozone/sciencem /missoz/index.html.

Vocabulary

  • ozone
  • ozone layer
  • ultraviolet rays
  • Antarctic ozone hole
  • Chlorofluorocarbons (CFCs)
  • Montreal Protocol
  • Environmental Protection Agency
  • Asthma
  • Cancer
  • Tropospheric ozone
  • Stratospheric ozone

Materials (for a class of 25)

  • Hygrometer (1 per class)
  • Infrared Thermometer (1 per class)
  • Ozone Test Strips (1 per class)
  • Ozone Scanner (1 per class)
  • Wind Vane (1 per class)
  • Thermal Glove (1 per class)
  • Cloud Charts (1 per class)
  • GLOBE Measurement Data Sheets (1 per student)
  • Computer
  • Access to Brainpop.com
  • Projection screen

Step-by-step suggested lesson plan

Instructor Activity Student Activity
Measurements. Take your students outside and conduct the GLOBE protocols. Students should set up the ozone strip, take the air and surface temperature, observe the sky for clouds, and measure humidity and wind direction. Students take measurements and write down their results on their data sheets.
Discussion. Ask students to think of examples of things that are good in one location, but bad somewhere else (e.g., a lion in a zoo, the flame of a candle, etc.). Explain that ozone is a gas that is “Good Up High, Bad Nearby”: up high it shields Earth from radiation, but nearby it is harmful to breathe. (See “Background Information” for details and links to resources). Students participate in brainstorming and answer related questions on p. 1.
Video. “Ozone Layer” on Brainpop.com provides a good overview of stratospheric ozone. Students watch video and answer related questions (p. 2)
Discussion: Go into more detail about “good” stratospheric ozone. Ex: How ozone is formed, where the layer can be found, and how it protects our health from UV rays. Students listen and answer questions: (p. 3)
Visual. Show students a picture of the ozone hole. Explain that the hole occurs over Antarctica each September, and that the Montreal Protocol has banned some of the air pollutants (CFCs) that cause it. Students listen and answer question: (p.3)
Measurements. Take your class outside, and scan the ozone strip. Also, retake the surface and air temperature, and the humidity so that students can take the average of these measurements to supplement their ozone measurements. Students take measurements and write down their results on their data sheets.

Expected outcomes

  1. Students can explain the “dual” nature of ozone – it can act as both a major air pollutant and as a layer of protection for the Earth.
  2. Students can define stratospheric ozone, know how it is formed, and know the causes and effects of ozone depletion.
  3. Students complete Lesson Four Journal Activities.

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Source:  OpenStax, Rice air curriculum. OpenStax CNX. May 09, 2010 Download for free at http://cnx.org/content/col11200/1.1
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