 Enthalpy

Adds up chemical energy and kinetic energy.

Wikipedia mentions however that the kinetic energy is often negligible, even for gases.

The sum is of interest when thinking about reactions because chemical reactions can change the number of molecules involved, and therefore the pressure.

To predict if a reaction is spontaneous or not, negative enthalpy is not enough, we must also consider entropy via Gibbs free energy.

Bibliography:

Enthalpy is a thermodynamic property that represents the total heat content of a system. It is denoted by the symbol \( H \) and is a state function, meaning its value depends only on the current state of the system, not on how it got there.