Chapter 17 “Reaction Rates and Equilibrium” Part 1: Reaction Rates Activated Complex Activation Energy is being supplied Reaction Rates #2.ppt Reaction Rates #2.ppt

Today you will learn… Effects of temperature on reaction rate Effects of concentration on reaction rate Effects of catalysts and inhibitors on reaction rate How catalysts affect reation rate

Factors Affecting Rate Temperature Increasing temperature increases the rate of a reaction. Surface Area Increasing surface area increases the rate of a reaction Concentration – Increasing concentration increases the rate of a reaction Presence of Catalyst – increases the rate unless an inhibitor is present

Temperature When we increase the temperature we give the particles energy This makes them move faster This means they collide with other particles more often So the reaction goes faster.

Temperature Increasing temperature increases KE Increasing KE means more particles have sufficient energy to overcome the activation energy barrier

This makes the reaction faster. Surface area If we make the pieces of the reactants smaller we increase the number of particles on the surface which can react. This makes the reaction faster. The particles on the surface can react When cut into smaller pieces the particles on the inside can react

Dissolve a sugar cube in warm water Surface area Dissolve a sugar cube in warm water 2 1 Dissolve granulated sugar in warm water

Surface Area Demo: Combustion of iron Combustion of flour

There are more particles in the same volume to react Concentration There are less red particles in the same volume, so there is less chance of a collision If we make one reactant more concentrated (like making a drink of Kool-Aid more concentrated) There are more particles in the same volume to react So the reaction goes faster. There are more red particles in the same volume so there is more chance of a collision, so the reaction goes faster

Concentration Demo: Elephant’s toothpaste

Catalysts Catalyst: A substance that speeds up a reaction, without being consumed itself in the reaction Enzyme: A large molecule (usually a protein) that catalyzes biological reactions. Human body temperature = 37o C, much too low for digestion reactions without catalysts.

Catalysts Inhibitors – interfere with the action of a catalyst; reactions slow or even stop Catalysts work by lowering the activation energy for a process

Endothermic Reaction with a Catalyst

Exothermic Reaction with a Catalyst