Activation Energy: A level Chemistry Definition
Written by: Alexandra Brennan
Reviewed by: Philippa Platt
Published
Last updated
What is activation energy?
Activation energy (Eₐ) is the minimum energy required for reactant particles to successfully collide and form products in a chemical reaction. It represents the energy barrier that must be overcome for a reaction to proceed.
In reaction profile diagrams, activation energy is shown as the difference between the energy of the reactants and the peak of the energy curve. Catalysts lower activation energy by providing an alternative reaction pathway with a lower energy requirement, increasing the reaction rate.


Understanding activation energy is crucial in A Level Chemistry, particularly in reaction kinetics, collision theory, and the effect of temperature and catalysts on reaction rates.
Activation Energy Revision Resources to Ace Your Exams
For more information about activation energy check out the following resources:
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