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