A reaction profile is a graph that shows how the energy of the chemicals changes during a reaction. Energy is on the vertical axis and the progress of the reaction is on the horizontal axis. A level line on the left shows the energy of the reactants and a level line on the right shows the energy of the products.
In an exothermic reaction the products are at a lower energy than the reactants. The curve starts high, rises to a peak, then falls to a lower level. The difference in height between reactants and products is the overall energy change, and it is shown with an arrow pointing down.
In an endothermic reaction the products are at a higher energy than the reactants. The curve starts low, rises to a peak, then ends at a higher level. The overall energy change is an arrow pointing up.
In both cases the curve rises to a peak first. The height from the reactants up to the top of the peak is the activation energy. When you draw a profile, label the axes, the reactants, the products, the activation energy and the overall energy change.
