Energy level diagrams

Energy level diagrams are used to model energy changes during reactions. They show the relative energy levels of the products and reactants.

Exothermic reaction

The energy level decreases in an exothermic reaction. This is because energy is given out to the surroundings.

Graph of energy against progress of reaction. Horizontal line represents reactants energy. Drops vertically as energy released. Horizontal line at a lower level represents products' energy.A downwards arrow shows that energy is given out

Endothermic reaction

The energy level increases in an endothermic reaction. This is because energy is taken in from the surroundings.

Graph of energy against progress of reaction. A horizontal line represents the reactants' energy. It rises vertically as energy is absorbed. A horizontal line at a higher level then represents the products' energy.An upwards arrow shows that energy is taken in
Question

Look at the energy level diagrams below. Which reaction is more exothermic?

Two graphs of the effect of energy being released from reactants.

The reaction shown by the second diagram is more exothermic. There is a greater difference in energy between the reactants and products. The green arrow is longer.