1. REACTION RATES & COLLISION THEORY Chemistry

2. What is a rate?  What does a rate involve?  In science, rate describes…

3. A Savings Rate

4. CO 2 Concentration Increase Rate

5. Heart Rate

6. Rates in Science  Rates in Science:  Change in “something”  PER TIME (divided by)  ALWAYS PER TIME!!!  TIME: s, min, hr, day, yr  Examples:  Moving Rate: mi/hr  Your Growth Rate: in/yr lb/yr lb/wk

7. Rates in Chemistry  Reaction Rate- Change in the amount of reactant or product per unit time.

8. More Rates in Chemistry  Rates can be measured by:  Change in Reactant per time  Change in Product per time  Reaction Rates ARE NOT constant throughout the reaction

9. Rate of Reaction from A Graph  Rate at any time:  Slope of the Tangent Line  This graph shows the rate of reaction after about 50 seconds

10. Collision Theory – To Explain Reaction Rates  In order to react: 1. Molecules/Atoms must collide to react 2. Must collide in the correct place 3. Must have enough energy when they collide

11. Geometry (orientation) of Collision  Molecules have to collide with the correct geometry (orientation) to react  On the right, only the first type of collision will react for this particular reaction

12. Energy Diagrams & Transition States  Transition state:  “Middle Product”  Occurs when reactants have enough energy  Ea (Activation Energy)  Energy barrier for the forward reaction

13. Energy of Collision  Reactants must overcome the Ea to react! Is this reaction endothermic or exothermic? What would the graph for the other type of reaction look like?

14. Energy Diagram Questions 1. Is this reaction exothermic or endothermic? 2. The energy change for this reaction is 50 kJ and the Ea for the forward reaction is 120 kJ. What is Ea for the reverse reaction?