Reaction energy diagram – exothermic vs endothermic

ChemistryEnergetics & ThermodynamicsAges 15–16

An enthalpy diagram plots the reaction path: reactants climb over the activation-energy barrier Ea, then drop to the product level (exothermic, ΔH < 0) or rise to a higher one (endothermic, ΔH > 0). A beaker with a thermometer shows the heat released or absorbed, q = n·|ΔH|. Students pick a reaction with a real ΔrH°298 value from the textbook, drag the peak to change Ea, and toggle a catalyst to see the path drop lower.