Collision Theory

This lesson covers collision theory, the concept of activation energy, and what makes a collision successful as required by the Edexcel GCSE Combined Science specification (1SC0). Collision theory explains why changing conditions (concentration, temperature, surface area, catalysts) affects the rate of reaction.

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What Is Collision Theory?

Collision theory states that for a chemical reaction to occur:

1. Reacting particles must collide with each other.
2. The collision must have sufficient energy — at least equal to the activation energy.
3. The particles must collide with the correct orientation (they must hit in the right way).

If either condition is not met, the collision is unsuccessful and the particles simply bounce apart unchanged.

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Activation Energy

The activation energy (Eₐ) is the minimum energy that colliding particles need in order to react. Every reaction has its own activation energy.