6.3 Explaining Reaction Rates

Concepts of Collision Theory

a system consists of particles in constant motion at speeds proportional to the temperature of sample. • chemical reaction must involve particle collisions...with each other and with the walls of the containers. • effective collision : a collision that occurs with sufficient energy and correct orientation for bonds to be broken and new bonds to form. • ineffective collision : particles rebound from the collision, essentially unchanged. **The rate of reaction depends on frequency of collisions and the fraction of collisions that are effective.

Activation Energy:

the minimum energy required for the reaction to occur

Activated Complex:

an unstable molecule containing partially broken and partially formed bonds representing the maximum potential energy point in the change

Transition State:

energy maximum where the activated complex is formed.

A catalyst works by

lowering the activation energy needed for a reaction to occur