So another way to define entropy would be as follows. Entropy is nature's way to spread energy evenly throughout a system. So if you have a reaction where the reactants have much more molecules than the product, then the equation or the reaction will tend to go right because there are less molecules on the product. Side than the reactive side. The last thing that we should talk about when we talk about entropy is the third law of thermodynamics. But before we get into that, let's define entropy mathematically using a formula.