OZONE DANCE

An activity with elementary school students developed by Dr. Mary Ann H. Smith, NASA Langley Research Center, February 1993. Purpose is to help students understand some of the chemistry and physics concepts involved in the stratospheric ozone layer.

Request 13 "volunteers": 11 "atoms" and 2 "UV rays"
Materials: 2 flashlights and 13 signs (1 EUV, 1 UVB, 1 C, 2 F's, 2 Cl's and 6 O's)

(NOTE: Sometimes it is necessary to press the "replay" link a couple of times to see the demonstration repeat.)

PART 1 - NORMAL OZONE PRODUCTION

  1. 3 pairs of children, each child wearing an O (oxygen) sign. Each pair holds hands and jiggles/bounces on balls of feet. They are O2 (oxygen) molecules. Replay

    animated gif showing example of dance step

  2. Student wearing EUV (Extreme UltraViolet) sign shines flashlight on the 3 O2 molecules. They begin to bounce (vibrate) faster. One pair breaks apart and each single O atom joins an O2 pair; now we have 2 O3 (ozone) molecules. Replay

    animated gif showing example of dance step

  3. Student wearing UVB (UltraViolet B) sign shines flashlight on the 2 O3 molecules. They bounce faster, and 1 "atom" leaves each molecule; the 2 single atoms join hands (bond) again, so that there are 3 O2 molecules again. Replay

    animated gif showing example of dance step

    Steps 2 and 3 may be repeated several times. Explain to students that ozone is formed and destroyed by ultraviolet light from the sun continuously in the unpolluted upper atmosphere about 30 kilometers above the ground.

    PART 2 - OZONE DESTRUCTION OF CFC'S (ChloroFluoroCarbons)

  4. Form a molecule of CFC-12: C (carbon) in the center, with 2 F's (fluorines) and 2 Cl's (chlorines) each holding onto the C with one hand. [A can of CFC-12 ("Freon 12") refrigerant is a good prop to introduce here.] Mention that CFC-12 is used in our refrigerators and air conditioners. CFC-12 molecule "leaks" from a faulty air conditioner and moves toward the 3 O2 molecules.

    animated gif showing example of dance step

  5. Student with EUV sign shines flashlight on the 3 O2's and on the CFC-12. All molecules "vibrate" faster, and the 2 Cl's break off the CFC-12 while one O2 molecule also splits. Replay

    animated gif showing example of dance step

  6. Each Cl attaches itself to a single O, forming 2 ClO (chlorine monoxide) molecules. Replay

    animated gif showing example of dance step

  7. Another O2 molecule splits, and one O from this pair joins the CF2 left behind from Step 5, holding onto the C's shoulders with both hands, to form CF2O (difluorophosgene), while the other O joins the remaining O2 to make a single molecule of O3 (ozone). Replay

    animated gif showing example of dance step

END RESULT:

In PART 2 (with CFC-12) we now have half as many ozone molecules as we did in PART 1 (unpolluted upper atmosphere). In the real upper atmosphere about 1% of the global ozone layer is being lost each year. This activity describes only one of many reactions which are destroying our ozone layer, allowing more UVB radiation to reach the ground. UVB is harmful to living things (e.g., causes sunburn and skin cancer in humans).

OPTIONAL PROPS FOR ADDITIONAL DISCUSSION:

  1. Photo of Upper Atmosphere Research Satellite (measures ozone and other chemicals in the upper atmosphere), available from Public Mail Office.
  2. Photo of 12-year sequence of false-color images of the Antarctic Ozone Hole, available from Public Mail Office.
  3. Bottle of sunscreen lotion, hat, and sunglasses (discuss ways to protect ourselves from increased UVB).

If you have further questions please contact Dr. Mary Ann H. Smith, NASA Langley Research Center, Mail Stop 401A, Hampton, VA 23681, (757) 864-2701

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