SCIENCE 911: Fight a Fire, Save the Ozone
The race is on to find a replacement for halon, a chemical that can extinguish a fire in seconds. For decades, halon has been the chemical of choice to put out fires in computer rooms, jet engines, even oil rigs. There's just one problem. Halon destroys the ozone layer and may not be manufactured any longer by law. Engineers and aviation specialists test various chemicals, in a search to find an effective replacement before the supply of halon runs out.
Notes & Discussion
Activity: UV Light and You
NOTES & DISCUSSION
Destruction of the ozone layer is one of the most critical issues facing us today. Here is some background information for your discussions.
- Where does the chemical compound halon gets its name? Halon is a compound composed of bromocarbons, carbon compounds containing bromine. On the periodic table of elements, bromine is found in the halogen family, hence the name halon.
- What other elements are related to halon? Two familiar elements in the halogen family are fluorine and chlorine, compounds known as chlorofluorocarbons or CFCs, which have been linked directly to deterioration of the earth's ozone layer. Studies show that bromocarbons also break down the ozone layer.
- What is ozone and how is it formed? When UV radiation penetrates the atmosphere, diatomic oxygen, O2, breaks apart and recombines to form ozone, O3. As UV radiation continues to penetrate this 25-mile wide band of ozone, the O3 is broken back down into O2 This process has been taking place for hundreds of millions of years. Result? The ozone layer. Ozone also can be found closer to the earth as a component of smog.
- What happens when the protective ozone layer disappears? Direct UV radiation from the sun reaches the earth's surface. Dangerous levels of UV radiation can weaken the immune system, cause cataracts, skin cancer and wrinkling. Sunscreens and blocks provide only some protection. UV radiation has also been shown to damage crops.
- Working with halogenated materials in the lab can be dangerous. A halide ion detection lab is one of the few safe activities that can be done in a classroom setting. Doing such a lab in microscale is even safer -- and easier. If you haven't tried one yet, a microscale lab means working with drops instead of large volumes of chemicals. You'll find such a suggested lab in the 1993 edition of Laboratory Experiments in Modern Chemistry, published by Holt, Rinehart & Winston, Inc.
ACTIVITY: UV LIGHT AND YOU
Test the effects of exposure to ultraviolet radiation on living cells by simulating the ozone hole in the lab. Then, consider how this information might apply to you.
Monitoring UV Radiation
The increasing size of the ozone hole is a great concern for many. Use the following experiment to investigate what happens to living creatures when the protective ozone layer disappears. This is also a good project for a science fair.
You will need:
- a selected organism to study, such as a plant, yeast culture, ant farm, algae, etc.
- a safe UV light source, such as the goggle box in your chemistry laboratory, tanning light, black light. (You can also use a fish tank with UV light, but the results won't be as dramatic.)
- a microscope, cell stains and slides (if desired).
- Collect initial data on your organism of choice by making physical observations on the size, shape, color, mass, texture, etc. Other suggestions include counting organisms or leaves, making microscopic slides for observation and measuring respiration.
- Use a safe source of UV radiation, such as the enclosed goggle box in the chemistry lab. Expose your organism to the UV light.
- Determine the variables that will control your experiment. Some suggested variables include:
- overall length of exposure
- type of UV bulb used
- length of time of the overall study
- type of food and liquid supplied
- Try a splash or squirt of suntan lotion or baby oil on one of the organisms.
- Predict what will happen. You should see some changes over time, especially in cell structure.
In addition to your formal write-up of this lab, consider:
- Based on your studies, could you hypothesize what might happen to human cells under the same condition?
- What concerns about UV light and the ozone layer do you have after completing this investigation?
- Evaluate your lifestyle. Can you do anything to change what is happening in the atmosphere or do you feel the dilemma of the ozone layer will not affect you?
- Find out more about how the ozone layer protects us from UV light. What reactions are going on when the UV light hits the ozone?
- Exposure to UV radiation undermines the immune system and may cause cataracts and skin cancer. What impact could continued ozone depletion have on a national health care system? Has the Clinton Administration accounted for the increasing number of cases of ozone-related illness?
- UV radiation can interfere with photosynthesis, causing lower crop yields. Discuss how reduced quantities of produce will affect the economy. Will this have an impact on the buying and eating habits of your family?
- Radiation has been found to slow the growth of phytoplankton, the mainstay of the ocean food chain. How will this affect marine life? What might increased levels of radiation do to the human food chain? Should we act now and take protective measures or wait until we are secure in our scientific findings?
- Ozone exists in huge quantities around major cities as a component of smog. Describe the reaction for producing ozone (smog) in the atmosphere. Why doesn't ozone at ground level protect the way the ozone layer does? Can you suggest ways in which we can replenish the ozone layer in the stratosphere?
Source: "Ozone Depletion," Congressional Quarterly Researcher, April 3, 1992.
- Use the Frontiers segment and this activity to enrich your study of chemical elements when you work with the periodic table. You can also apply the concepts to environmental science.
- The experiment to monitor exposure to UV light can be used as a biochem lab or as a long-term research activity, even as a science fair project. The critical thinking questions can be used with a range of subject areas.
CREDIT: Amy Fradkin, who contributed this activity, is in her third year of teaching chemistry. She began her teaching career at Naugatuck High School in Naugatuck, Connecticut, and is now at King Philip Regional High School in Wrentham, Massachusetts.
- According to the Environmental Protection Agency, every 50,000 cars in the U.S. emit 1,000,000 pounds of halogenated compounds per year from car air-conditioners. How much is that in metric tons? Find out how we compare to other countries by doing online or library research in science newsmagazines.
Scientific American Frontiers
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