Kinetics Lesson 3 Collision Theory The Collision Theory Link to Simulation of Molecular Motion 1. Matter is moving particles. 2. Temperature increases- particles move faster -more collisions -more collision energy. 3. Chemical reactions -bonds break -new bonds form 4. Collisions provide the energy. Collision Theory You need a collision to have a reaction. Collisions provide the energy required to break bonds. Most collisions are not successful Collision Theory A successful collision requires: 1. Favourable Geometry products Poor Geometry no products 2. Sufficient Energy to break the chemical bonds Activation energy is the minimum amount of energy required for a successful collision. The Collision Theory can be used to explain how the rate of a reaction can be changed. Reaction rates can increase due to 1. More collisions 2. Harder collisions- greater collision energy 3. Lower activation energy or Ea- low energy collisions are more effective. And that’s it! The Collision Theory can be used to explain how the rate of a reaction can be changed. 1. Increasing the temperature increases the rate because there are: More collisions Harder collisions 2. Increasing the reactant concentration increases the rate because there are: More frequent collisions The Collision Theory can be used to explain how the rate of a reaction can be changed. 3. Adding a catalyst Lowers the activation energy or Ea- allowing low energy collisions to be successful The catalyst KI is added to H2O2, food colouring, and dishwashing detergent. The O2 produced makes foam. Movie The Collision Theory can be used to explain how the rate of a reaction can be changed. 4. Changing the nature of the reactant for a more reactive chemical increases the rate Lower activation energy or Ea- allowing low energy collisions to be successful The Collision Theory can be used to explain how the rate of a reaction can be changed. 5. Increasing the surface area of a solid reactant increases the rate because: More frequent collisions Explain each Scenario Using the Collision Theory 1. A balloon full of H2 and O2 do not react at room temperature. Ea is too high for the room temperature collisions A small spark ignites causes an explosion. The spark provides the Ea and it explodes because it is exothermic Explain each Scenario Using the Collision Theory 2. A candle does not burn at room temperature Ea is too high for the room temperature collisions A match causes the candle to burn The match provides the Ea The candle continues to burn It burns because it is exothermic Explain each Scenario Using the Collision Theory 3. H2O2 decomposes very slowly at room temperature. 2H2O2(aq) → O2(g) + 2H2O(l) KI increases the reaction rate dramatically. KI is a catalyst as it is not a reactant and it speeds up the rate. Lowers the Ea- allows low energy collisions to be successful Describe and Graph the Relationship between the Following Ea and the rate Decreasing the Ea increases the rate- inverse. Rate Ea Describe and Graph the Relationship between the Following Temperature and the rate Increasing the temperature increases the rate- direct. Rate Temp Describe and Graph the Relationship between the Following Concentration and the rate Increasing the concentration increases the rate- direct. Rate Conc Describe and Graph the Relationship between the Following Ea and the temperature The only way to change the Ea is by adding a catalyst! No relationship! Temp Ea Which factors increase the percentage of successful collisions? I. Increasing temperature II. Increasing concentration III. Increasing surface area IV. Adding a catalyst