Thermochemistry is a sub-branch of physical chemistry and thermodynamics which concerns itself with the energy that changes or is absorbed in the context of physical transformations and chemical reactions. Popular examples of the subjects of thermochemistry would be the energy shifts and integration in melting or boiling.

Essentially, what you would be typically observing or looking out for when you study thermochemistry would be the exchange of energy in processes that involve transformation. This will include chemical reactions, mixing, and phase transitions. Thermochemistry also requires you to making calculations with regards to the quantities of enthalpy, heat capacity, heat combustion and yes, free energy.


It is interesting to note that the principles or laws that practically defined the whole of thermochemistry would later aid in the formulation of the First Law of Thermodynamics. These two laws are Lavoisier and Laplace’s Law (which state that “the heat exchange accompanying a transformation is equal and opposite to the heat exchange accompanying the reverse transformation”), and Hess’ Law (which states that “the heat exchange accompanying a transformation is the same whether the process occurs in one or several steps”).

In this section of the site, we will be providing you with all the information necessary to understand thermochemistry.