Consider a reaction equation:
A + B → C
Let us say that the total energy of the reactants A and B is 45kJ. (This is you before you do some work).

And after they react, they become a new product called C that now has an energy value of 25kJ. This is you after you did some work.
You have lost energy (-20kJ). The minus reminds you that you have LOST the energy.
In chemical reactions, this difference in energy between reactants and products is called “Heat of Reaction”. (ΔH = -20kJ)

In chemistry there is a natural barrier preventing chemicals from reacting. This barrier is called the Activation Energy.
For our example, let us assume that the barrier (Activation Energy) is 65kJ.
We can draw a graph showing all these energy values.

• 45kJ = Initial Potential Energy of Reactants
• 55kJ = Activation Energy (Energy needed to overcome barrier)
• 100kJ = Energy of the Activated Complex (In between state, neither reactants nor products)
• 25kJ = Final Potential Energy of Products
• -20kJ = Heat of Reaction (Change in the Reactants Energy Value)

By using CATALYSTS, the energy barrier (Activation Energy) can be decreased, thus allowing the reaction to run faster.