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Decomposition Reactions

A Compound breaks down into two or more simpler substances.

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What's That Hole in the Sky?

What's That Hole in the Sky?

Credit: NASA
Source: http://en.wikipedia.org/wiki/File:GPS_Satellite_NASA_art-iif.jpg
License: CC BY-NC 3.0

Refrigerators as environmental contaminants? Hard to believe, but at one time this was true. Compounds used as coolants were implicated in ozone destruction. These materials were low-molecular weight, easily compressed, and worked well to cool items in a refrigerator. However, they also readily leaked into the atmosphere and created major environmental problems.

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  • Chorofluorocarbons (CFCs) were once widely used as refrigerants and propellants in spray cans. As a result, large amounts of these materials escaped into the upper atmosphere. By 1990, over 750 ppm of the major CFCs were detected in the stratosphere.
  • By the early 1970s, CFC breakdown had been well-documented. A CFC molecule would lose a chlorine atom when struck by UV light. This chlorine atom would then break up an ozone (O3) molecule, forming O2 and chlorine monoxide (ClO). When a free oxygen atom comes in contact with the ClO, the products are O2 and a chlorine atom, now available to attack another ozone molecule.
  • International agreements led to the 1987 Montreal Protocol, in which countries committed to drastic reduction in CFC production and use (50% reduction by 1998, for example). Since the adoption of the protocol, ozone losses have leveled off, but it will be several years before they begin to rebuild.
  • Credit: NASA
    Source: http://www.flickr.com/photos/gsfc/4994781316/
    License: CC BY-NC 3.0

    The hole in the ozone layer as of September, 2010 [Figure2]


  • While depletion of upper-atmosphere ozone is a problem, ground level ozone increases are also a significant health issue. This ozone is created from a series of reactions between nitrogen oxide compounds, volatile organic compounds, and sunlight. With more cars and trucks on the roads, along with increased release of materials from industry and power utilities, this form of ozone is on the rise. Breathing ozone can aggravate a number of lung problems, including asthma (a problem for over 25 million people in the U.S., including 7 million children). It can also cause coughing, throat irritation, and lung disease.
  • Watch a video at the link below to learn more about the ozone layer: https://www.youtube.com/watch?v=XLY8m-dXOxo

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Use the links below to learn more about the ozone layer. Then answer the following questions.

  1. What causes the low temperature in a refrigerator?
  2. Where is most ozone concentrated in the upper atmosphere?
  3. What were the two major sources of CFCs?
  4. What does the ozone layer do?
  5. What are some health problems associated with increased exposure to UV light?

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    Image Attributions

    1. [1]^ Credit: NASA; Source: http://en.wikipedia.org/wiki/File:GPS_Satellite_NASA_art-iif.jpg; License: CC BY-NC 3.0
    2. [2]^ Credit: NASA; Source: http://www.flickr.com/photos/gsfc/4994781316/; License: CC BY-NC 3.0

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