Activation Energy

To illustrate the principle of activation energy in a non-chemical fashion, we return to the leaning tower of Pisa model used in our discussion of thermodynamic stability. Imagine that a one meter high solid wall is built around the highest potential energy level (7) of the tower. If a heavy iron ball is placed on the floor of this level it will have a high potential energy, as noted earlier. However, even if the ball is given a strong shove toward the edge of the level, the wall prevents this high potential energy from being released by falling. In order to use the inherent potential energy of this system we must invest an initial "activation energy" by lifting the ball to the top of the wall. Indeed, if the wall were very high this might not be possible. Such activation energy requirements are common in most chemical reactions.