Collision Theory of Reactions

1. Reactions occur when two or more atoms and/or molecules collide with sufficient energy and in the correct orientation.
2. Factors which affect reaction rates
   1. Surface area of solid reactants. Why?
   2. Concentration of reactants. Why?
   3. Temperature of reactants. Why?
   4. Catalysts
      1. A catalyst is a substance which speeds up the rate of reaction without being used up in the reaction. You will have the same amount of catalyst at the beginning and end of a reaction, but the reaction will occur much more quickly.
      2. Catalyst examples:
         1. Most of the enzymes in your body are catalysts. Many of the chemical reactions that are necessary for life to occur run too slowly without being catalyzed by an enzyme. Without catalysts we could not exist.
         2. The catalytic converter that is part of all modern car exhaust systems. This turn many of the pollutants (primarily hydrocarbon (C-H) fragments and carbon monoxide (CO) in the exhaust into carbon dioxide (CO₂) and water (H₂O).
         3. When you generated oxygen from hydrogen peroxide earlier this year you used a Manganese metal catalyst.

            2 H₂O₂ ---> 2 H₂O + O₂
            Notice that the Mn (Manganese) is not written as part of this reaction. That is because it is not consumed during the reaction. It can be reused over and over again.

         4. Chlorine atoms from CFCs (chlorofluorocarbons) catalyze the breakdown of ozone into oxygen: O + O₃ ---> 2 O₂
      3. See some catalyzed reactions:
         1. Film: Forensic Catalysis
         2. Film: Formic Acid Decomposition

    

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