The energy hill sim
An energy level diagram shows only two levels, the reactants and the products, and ΔH between them.
The energy hill · covers the GCSE, IGCSE, O-Level topic
What the sim shows
An energy level diagram shows only two levels, the reactants and the products, and ΔH between them. A reaction profile adds the hill: the activation energy, Eₐ, is the climb from the reactant level to the top, and it is always positive. ΔH = energy of products − energy of reactants: negative (products lower) for an exothermic reaction, positive for an endothermic one. A catalyst gives another path with a lower hill; the two levels do not move, so ΔH is the same. Breaking bonds takes energy in and making bonds gives energy out, so ΔH = bonds broken − bonds made. Only a collision with at least Eₐ reacts. The energy axis has no numbers: each chart is drawn to its own scale. Values marked illustrative are this desk's, chosen to draw the hill. For hydrogen peroxide with manganese(IV) oxide, MnO₂, the lesson's 49 kJ/mol is the value usually quoted for platinum; values for MnO₂ vary, so the hill is drawn at 49 and marked illustrative.
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