Activation Energy and Catalysts

This lesson explores activation energy in greater depth and examines how catalysts affect the energy requirements of reactions. Understanding the link between activation energy, catalysts, and reaction profiles is essential for the Energy Changes topic in AQA GCSE Combined Science Trilogy (8464).

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What Is Activation Energy?

Activation energy ($E_a$Ea​) is the minimum amount of energy that reacting particles must have when they collide in order for a reaction to occur. It is the energy needed to start breaking bonds in the reactants.

$E_a = \text{Energy at the peak of the reaction profile} - \text{Energy of the reactants}$Ea​=Energy at the peak of the reaction profile−Energy of the reactants

Even in highly exothermic reactions, an initial energy input is needed. This is why fuels do not spontaneously combust at room temperature — the activation energy barrier must be overcome first (e.g., by a spark or a match).

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Activation Energy and Collision Theory

For a reaction to occur, particles must:

1. Collide with each other.
2. Have sufficient energy (at least equal to $E_a$Ea​).
3. Collide with the correct orientation.