Which statement correctly describes the effect of changing reaction conditions on the activation energy (EaE_{\text{a}}Ea) of a chemical reaction?
Increasing the temperature increases the fraction of molecules with energy ≥Ea\ge E_{\text{a}}≥Ea by lowering the activation energy.
Decreasing the particle size of a solid reactant lowers the activation energy.
Adding a catalyst provides an alternative pathway with a lower activation energy.
Increasing the concentration of reactants decreases the activation energy so more collisions are successful.
31 exam-style questions on OCR GCSE Chemistry Controlling reactions. Each one has a worked solution and a mark scheme showing where the marks go.