Catalysis and Activation Energy

In 1985, scientists began to notice something troubling with Earth's atmosphere. These scientists, and many in the general public, became concerned about studies showing a major treat to the environment. In the upper layers of Earth’s atmosphere, there are traces of of a gas known as ozone. Ozone is composed of three oxygen molecules. This triatomic oxygen protects the Earth from the Sun’s harmful ultraviolet rays. As studies continued, it was determined that concentrations of ozone gas were thinnest over Antarctica. What caused ozone to suddenly begin to disappear? Chemists suspected the culprit, or catalyst, was chlorofluorocarbons (CFC’s). CFC’s had been used primarily in refrigerants, air conditioners, and as propellants in aerosol sprays. Once released into the atmosphere, the chlorine molecule from the CFC’s acts as a catalyst to transform ozone into oxygen. In other words, it breaks up the ozone molecule. The production of CFC’s were banned in 1996, along with any coolant that contains the substance. In chemistry, many substances act as a catalyst in reactions. In this topic, you will investigate some different catalysts and how they affect chemical reactions.

Essential Question

• What is a catalyst, and how does a catalyst affect a chemical reaction?