Thermodynamics is summarized in three laws.

The first law of thermodynamics is a conservation of energy law.

   The energy gained by a system is supplied by its surrounding, or

   The energy gained by the surroundings is supplied by a system.

The second law of thermodynamics is:

   The entropy of the universe is always increasing.

The third law of thermodynamics is:

   The entropy of a pure, perfectly-ordered crystalline solid is zero at absolute zero.

To apply these laws to a chemical reactor, chemists define state functions at constant pressure (atmospheric pressure usually). These functions of enthalpy, entropy, and free energy are measured and tabulated to help chemists predict the sponteneity, energy requirements, or energy production. These functions are independent of pathways and may be combined to determine the ideal energy transfers possible.

By looking at the free energy under different conditions, the chemist may be able to shift the equilibrium of a reaction by changing the conditions of the reaction.

Work done by a chemical reaction is NOT a state function. It may vary depending on the specific geometry of a system, but maximum work possible is determined by the first and second laws.