Thermochemistry

Hess's law states that the total heat release or absorption in a chemical reaction is constant, regardless of the pathway taken. It was a significant contribution to the field of thermochemistry and hinted at the laws of thermodynamics.
 Germain Henri Hess Russia 1840 Thermochemistry

Hess's law states that the total heat release or absorption in a chemical reaction is constant, regardless of the pathway taken. It was a significant contribution to the field of thermochemistry and hinted at the laws of thermodynamics.