Activation Energy and Catalysts

Activation energy is the energy barrier that must be overcome for a chemical reaction to occur. Catalysts are substances that lower this barrier, making reactions faster and more efficient. This lesson covers these concepts in detail as required by the AQA GCSE Chemistry specification, linking them to reaction profiles and collision theory.

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What Is Activation Energy?

Activation energy (Ea) is the minimum amount of energy that colliding particles must have in order to react. Even if particles collide, they will only react if they have enough energy to break the existing bonds in the reactants.

Think of activation energy as an energy hill that reactant particles must climb over before they can form products. If they do not have enough energy, they simply bounce off each other without reacting.

Key Point	Detail
Definition	Minimum energy required for a reaction to occur
Unit	kJ/mol (kilojoules per mole)
On a reaction profile	Shown as the height from the reactants to the peak of the energy barrier
Applies to	Both exothermic AND endothermic reactions