An energy picture of the reaction
A reaction profile shows energy on the y-axis and reaction progress on the x-axis. The left level is the reactants; the right level is the products. It does not show temperature against time.
Lesson 5.5 · AQA Combined Science
Reaction profiles and activation energy
Two arrows with different meanings
Activation energy is the minimum energy particles must have to react. Draw its arrow from the reactant level up to the peak. Reacting particles must collide with sufficient energy.
Overall energy change is the difference between reactant and product levels. Draw this arrow between those two levels, not from the peak.
Draw it in four steps
1. Label the axes: energy and reaction progress.
2. Add reactant and product levels. Exothermic products are lower; endothermic products are higher.
3. Join the levels with a smooth curve rising to a peak above both levels.
4. Add the activation-energy and overall-energy-change arrows.
Remember
Exothermic products lower; endothermic products higher. Activation energy: reactants up to the peak.
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