Final answer:
The diagram demonstrates an exothermic reaction, where heat energy is released from the system to the surroundings.
Step-by-step explanation:
The diagram below demonstrates an exothermic reaction. In an exothermic reaction, heat energy is released from the system to the surroundings. This is evident in the diagram when the products have less stored energy than the reactants. The potential energy of the system decreases as energy is released to the surroundings. This indicates that the reaction is exothermic.