It is true that in most spontaneous chemical reactions, energy or enthalpy falls. The energy that the chemical substances lose during reaction is given off as heat.

Another way of expressing the situation is to say that most spontaneous chemical processes are exothermic.

The combustion of gasoline, like all combustions, liberates heat, because the carbon dioxide and water molecules produced have lower energy than the gasoline and oxygen molecules from which they came.

Is it valid to state as a general law that all spontaneous reactions go in the direction of lower energy, or that all spontaneous reactions are exothermic?