IIIIIIIVV Reaction Rates

Collision Theory n Reaction rate depends on the collisions between reacting particles. n Successful collisions occur if the particles collide with each other 2. have the correct orientation 3. have enough kinetic energy to break bonds

Collision Theory n Particle Orientation Required Orientation Successful Collision Unsuccessful Collisions

Collision Theory n Activation Energy (E a )  minimum energy required for a reaction to occur Activation Energy

Collision Theory n Activation Energy  depends on reactants  low E a = fast rxn rate EaEa

Exothermic Reaction

Endothermic Reactions

Factors Affecting Rxn Rate n Surface Area  high SA = fast rxn rate  more opportunities for collisions  Increase surface area by… - using smaller particles - dissolving in water

Factors Affecting Rxn Rate n Concentration  high conc = fast rxn rate  more opportunities for collisions

Factors Affecting Rxn Rate n Temperature  high temp = fast rxn rate  high KE - fast-moving particles - more likely to reach activation energy

Factors Affecting Rxn Rate n Temperature Analogy: 2-car collision 5 mph “fender bender” 50 mph “high-speed crash”

Factors Affecting Rxn Rate n Catalyst  substance that increases rxn rate without being consumed in the rxn  lowers the activation energy

Factors Affecting Rxn Rate n Enzyme Catalysis