On a reaction profile, activation energy is measured from
the top of the barrier to the product level only
the product level to zero energy
the reactant level to the product level only
the reactant energy level to the top of the energy barrier
94 exam-style questions on Edexcel GCSE Chemistry 8.2 Heat energy changes in chemical reactions, covering 8.2.1 Exothermic and endothermic changes, 8.2.2 Bond breaking, bond making and overall energy change, 8.2.3 Calculating energy change from bond energies, and 8.2.4 Activation energy and reaction profiles. Each one has a worked solution and a mark scheme showing where the marks go.