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Purpose: to show how the annual
ozone depletion that occurs over Antarctica
results in less protective ozone over our
heads. CLICK HERE to view the many video-demonstrations I have posted online. Each video is 2 - 4 minutes long.
Materials: 1. 8 oz. of Cool Whip non-dairy topping 2. red food coloring 3. whisk-type stirrer 4. two white, opaque lids from 8 oz. Cool Whip containers (the Cool whip lids work best because they are white and opaque) 5. frosting spreader? (anything you'd use to spread frosting onto a cake) 6. a bowl (about twice the size of the 8 oz. container of topping) 7. a large spoon Background: Each year several factors work together to cause intense ozone depletion over Antarctica (four are listed below). Although the hole cannot be seen, over 50% of the ozone is destroyed over this region each Spring (September - November). 1. the Polar Vortex: During the winter, the air over Antarctica becomes isolated from the rest of the atmosphere. For months, it swirls around in a giant vortex. 2. clouds in the stratosphere: The South Pole is so cold that clouds of ice crystals are present in the stratosphere where ozone is most abundant. These ice crystals are crucial to the depletion of ozone, providing a workbench for the destructive chemistry. 3. CFCs: Manmade chloroflourocarbons used over past decades ascend to the ozone layer where chlorine is freed, and begins its destructive chemistry. 4. sunlight: Each spring, sunlight begins to shine on the stratosphere over Antarctica. The sunlight is involved with breaking apart the CFC molecules. Procedures: 1. Use a permanent marker to sketch N. America, S. America, and Antarctica onto the underside of each Cool Whip lid to make each look like the Earth. One of these "worlds" will be the control (CFCs were never invented). 2. Put half of the topping (4 oz.) and 20-25 drops of the red food coloring into a bowl. Stir it until the color is a uniform pink. 3. Spread half of this pink topping onto one "world" and half onto the other. The topping represents the atmosphere, and the pink represents ozone. 4. Set one "world" aside (the control) and then with the other, make a "hole" in the ozone over Antarctica by removing some topping and replacing it with white topping. Emphasize that you would not be able to see the hole, but scientific instruments (satellites, etc.) would be able to detect it. The white area represents "the hole" that is present over Antarctica each spring. 5. After showing the students, use the whisk strirrer to mix up the atmosphere until the color is a uniform pink. This represents what happens as the polar vortex "breaks up" with the approaching summer. Use the frosting spreader to smooth out the pink topping. Point out that the atmosphere is slightly "less pink" worldwide. Remember, pink is good. . . because the pink color means ozone is present . 6. Repeat steps 4 and 5 three more times. Compare the ozone depleted Earth to the one that has experienced no depletion. The moral of the story: Although the mixing of ozone-depleted air with the rest of our atmosphere may not be as simple, or as complete as the type of "dilution" that you've just demonstrated, it is very similar. This is what has caused "nonpolar" depletion of ozone, amounting to about 3 % per decade recently. Some Ozone Facts 1. The natural concentration of ozone in the atmosphere is remarkably small. . . If all the ozone molecules were located on the Earth's surface at atmospheric pressure, they would form a layer only 3 mm thick. 2. British researchers began monitoring ozone levels in 1956. 3. In 1985, British scientists began finding dramatic declines in ozone values over Antarctica each spring. . . a "hole" in the ozone layer where concentrations are depleted by over 50 %. 4. A similar depletion happens over the north polar region each spring, but it has not been intense enough to be called a "hole". 5. The annual hole over Antarctica has grown to be about the size of North America during some years. 6. ChloroFlouroCarbons (CFCs) were developed in the 1930's. Freon, the most famous CFC, has been used in refrigeration and air conditioning systems. |
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