Two side-by-side diagrams. - The diagram on the left is titled "Reaction Energy-Exothermic" and displays how energy is released. A line for the reactants moves horizontally on the diagram, then curves up when the energy is released, and drops down as the end product. - The diagram on the right is titled "Reaction Energy-Endothermic" and displays how energy is absorbed. A line for the reactants moves horizontally at the bottom of the diagram, then curves up dramatically when the energy is absorbed. The line dips down slightly as the end product.