The world’s first ice-calorimeter, used in the winter of 1782-83, by Antoine Lavoisier and Pierre-Simon Laplace, to determine the heat evolved in various chemical changes; calculations which were based on Joseph Black’s prior discovery of latent heat. These experiments mark the foundation of thermochemistry.

In 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:^[1] Image File history File links Download high-resolution version (638x1069, 226 KB) From Antoine Lavoisiers 1787 Elements of Chemistry. ... Image File history File links Download high-resolution version (638x1069, 226 KB) From Antoine Lavoisiers 1787 Elements of Chemistry. ... Antoine-Laurent de Lavoisier (August 26, 1743 – May 8, 1794) the father of modern chemistry, was a French nobleman prominent in the histories of chemistry, finance, biology, and economics. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... In physics, heat, symbolized by Q, is defined as transfer of thermal energy [1] Generally, heat is a form of energy transfer associated with the different motions of atoms, molecules and other particles that comprise matter when it is hot and when it is cold. ... A chemical change involves the change in a substance through chemical reactions. ... Joseph Black Joseph Black (April 16, 1728 - December 6, 1799) was a Scottish physicist and chemist. ... In thermochemistry, latent heat is the amount of energy in the form of heat released or absorbed by a substance during evaporation. ... Thermodynamics (from the Greek θερμη, therme, meaning heat and δυναμις, dunamis, meaning power) is a branch of physics that studies the effects of changes in temperature, pressure, and volume on physical systems at the macroscopic scale by analyzing the collective motion of their particles using statistics. ... Physical chemistry is the application of physics to macroscopic, microscopic, atomic and particulate phenomena in chemical systems[1]within the field of chemistry traditionally using the principles, practices and concepts of thermodynamics, quantum chemistry, statistical mechanics and kinetics. ... In physics, heat, symbolized by Q, is defined as transfer of thermal energy [1] Generally, heat is a form of energy transfer associated with the different motions of atoms, molecules and other particles that comprise matter when it is hot and when it is cold. ... Vapours of hydrogen chloride in a beaker and ammonia in a test tube meet to form a cloud of a new substance, ammonium chloride A chemical reaction is a process that results in the interconversion of chemical substances. ... In physics, a phase transition, (or phase change) is the transformation of a thermodynamic system from one phase to another. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... It has been suggested that this article or section be merged with Heating value. ... The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 100 kPa...

1. Lavoisier and Laplace’s law (1782): the heat exchange accompanying a transformation is equal and opposite to the heat exchange accompanying the reverse transformation.
2. 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); it can be shown, however, that they are a direct consequence of it. To meet Wikipedias quality standards, this article or section may require cleanup. ... The first law of thermodynamics, a generalized expression of the law of the conservation of energy, states: // Description Essentially, the First Law of Thermodynamics declares that energy is conserved for a closed system, with heat and work being the forms of energy transfer. ...

History

In 1782 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. Similarly, in 1840 Russian chemist Germain Hess formulated the principle that the evolution of heat in a reaction is the same whether the process is accomplished in one-step or in a number of stages. This is known as Hess's law. With the advent of the mechanical theory of heat in the early 19th century, Hess’s law came to be viewed as a consequence of the law of conservation of energy. Antoine-Laurent de Lavoisier (August 26, 1743 – May 8, 1794) the father of modern chemistry, was a French nobleman prominent in the histories of chemistry, finance, biology, and economics. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... The specific heat capacity (symbol c or s, also called specific heat) of a substance is defined as heat capacity per unit mass. ... In thermochemistry, latent heat is the amount of energy in the form of heat released or absorbed by a substance during evaporation. ... Germain Henri Hess (1802-08-07 - 1850-11-30) was a Swiss chemist and doctor who formulated Hesss Law, an early principle of thermochemistry. ... A visual representation of the law in action. ... In the history of science, the theory of heat or mechanical theory of heat was a theory, introduced predominately in 1824 by the French physicist Sadi Carnot, that heat and mechanical work are equivalent. ... Conservation of energy states that the total amount of energy in an isolated system remains constant, although it may change forms (for instance, friction turns kinetic energy into thermal energy). ...

See also

• Important publications in thermochemistry
• Isodesmic reaction
• Principle of maximum work
• Reaction Calorimeter
• Thomsen-Berthelot principle
• Thermodynamic databases for pure substances

This is a list of important publications in chemistry, organized by field. ... An isodesmic reaction is a chemical reaction in which the type of chemical bonds broken in the reactant are the same as the type of bonds formed in the reaction product. ... In thermochemistry, the principle of maximum work was a postulate put forward in 1875 by the French chemist Marcellin Berthelot which stated that chemical reactions will tend to evolve in such a manner so as to assemble or dissasemble chemical species so to yield the maximum amount of chemical energy... A reaction calorimeter is an instrument that enables the energy being released or absorbed by a reaction to be measured. ... In thermochemistry, the Thomsen-Berthelot principle is an hypothesis in the history of chemistry which argued that all chemical changes are accompanied by the production of heat and that processes which occur will be ones in which the most heat is produced. ... Thermodynamic databases contain information about thermodynamic properties for substances, the most important being enthalpy, entropy, and Gibbs free energy. ...

References

External links

• Thermochemistry - Britannica (1911)
• Thermochemistry - an overview