1. States that atoms, ions, and molecules must collide
Collision Theory:
States that atoms, ions, and molecules must collide
in order to react.

2. Collision Theory:
According to collision theory, particles will react to form products if they collide with enough kinetic energy.
Particles that do not have enough energy to react bounce apart unchanged when they collide (no reaction).

3. When two reactant particles collide, they may form an activated complex.
An activated complex (transition state) is an unstable arrangement of atoms that forms for a moment at the peak of the activation-energy barrier.
The activated complex forms only if the colliding particles have enough energy and correct orientation.

4. Enough energy ? (minimum amount of energy required)
Activation Energy barrier
Activated
Complex
(minimum
amount
of energy
required)

5. An effective collision of oxygen and hydrogen molecules produces water molecules.
Activated Complex
2 H2 + O2
2 H2O

6. An ineffective collision of oxygen and hydrogen molecules produces no reaction; the reactants bounce apart unchanged.
2 H2 + O2
Activated Complex
2 H2 + O2

7. The Activation-energy barrier must be crossed before reactants are converted into products:
Exothermic Reaction
Endothermic Reaction

8. Particles must collide with: (Effective collision)
Favorable (correct) orientation to form the activated complex (transition state).
Sufficient energy to form the activated complex, and overcome the Activation Energy, Ea (minimum amount of energy required for a reaction to occur)

9. Energy absorbed by reaction
Reaction progress
Activated Complex
Activation Energy Ea
Products
Energy absorbed by reaction ∆H
Reactants
(Endothermic reaction)