thermochemistry - History

The study of the energy changes accompanying chemical reactions. Such energies have precise values for precisely defined reactants and products. Thermochemical methods are widely used in determining the energy value of foods.

In the thermodynamics and physical chemistry, thermochemistry is the study of the heat evolved or absorbed in chemical reactions. Thermochemistry, generally, is concerned with the heat exchange accompanying transformations, such as mixing, phase transitions, chemical reactions, etc., which includes calculations of such quantities as the heat capacity, heat of combustion, heat of formation, etc. The laws of thermochemistry rest on two statements:

Lavoisier and Laplace’s law (1780): the heat exchange accompanying a transformation is equal and opposite to the heat exchange accompanying the reverse transformation. Hess’s law (1840): the heat exchange accompanying a transformation is the same whether the process occurs in one or several steps

Both laws preceded the first law of thermodynamics (1850);

History

In 1780 Antoine Lavoisier and Pierre-Simon Laplace laid the foundations of “thermochemistry” by showing that the heat evolved in a reaction is equal to the heat absorbed in the reverse reaction. They also investigated the specific heat and latent heat of a number of substances, and amounts of heat evolved in combustion.