Collision Theory

The collision theory states that:
  1. The particles of the reacting need to touch to enable formation or breaking of the bonds for a reaction to happen.
  2. Collisions of particles of a reacting substance need to achieve a certain minimum energy (Activation Energy) in order to produce a reaction.
  3. Particles that collide also need to have the correct orientation of collision.

Activation Energy

  1. The activation energy is the minimum energy that the reactants particles must achieve at the time of collision in order for a chemical reaction to take place.
  2. The value of the activation energy is different for different reactions.
  3. A reaction with high activation energy occurs slowly whereas a reaction with a low activation energy occurs fast.

Effective Collision

Effective collision is the collision that produces a reaction achieving minimum energy that is sufficient and with a correct orientation of collision.

Energy Profile Diagram

In the diagram of energy profile, the activation energy is shown by the difference in energy between the peak of the graph and the level of the energy of the reacting substance.

Exothermic Reaction


Endothermic Reaction


Frequency of effective collision with rate of reaction and factors that affect the rate of reaction

  1. The frequency of effective collision is the number of effective collisions which occur in 1 second.
  2. The rate of reaction depends on the frequency of effective collisions that occur.
  3. If the frequency of an effective collision for a reaction is high, then the rate of reaction is also high.