Theories of Heat: Lavoisier to Count Rumford and Sir Humphry Davy


By Robert Hazen, Ph.D., George Mason University

Newton was unable to solve the riddle of heat and its companion phenomenon—light, which baffled researchers well into the 19th century. How did the theories of heat evolve and who were the geniuses who contributed to the understanding of these theories?

Image of an open and closed cup of tea along with a thermos flask to explain the concepts of mass and heat transfer
Thermodynamics is the study of heat in motion or how heat moves. (Image: Nandalal Sarkar/Shutterstock)

The nature of heat was a matter of intense debate for centuries. On the one hand, there were supporters of the caloric theory of heat; often associated with the influential French chemist Antoine Laurent Lavoisier. On the other hand, there were Count Rumford and Humphry Davy who debunked the caloric theory.

 Evolution of Thermodynamics

Thermodynamics is literally the study of heat in motion or how heat moves. Unlike Newton’s laws of motion, the laws of thermodynamics did not spring forth fully formed from one mind.

The heat theories and other ideas emerged gradually from many, many different researchers. It was in the early- and mid-19th century that the laws of thermodynamics were finally formulated and understood in a systematic way. 

Learn more about the nature of science.

Antoine Laurent Lavoisier’s Contributions

Antoine Laurent Lavoisier lived from 1743 to 1794. He rose to a position of power and prestige in pre-revolutionary France. Despite being a lawyer, he soon turned to science as he was enthralled by chemistry and mineralogy.

Lavoisier was the champion of liberal social reform and he worked within the existing political system to try and implement those reforms. During the French Revolution, however, he was targeted as a sympathizer of the former regime. Subsequently, he was executed by guillotine on May 8, 1794. French mathematician Joseph-Louise Lagrange regretted the execution of Lavoisier.

Lavoisier and the Caloric Theory of Heat

The scientific work of Lavoisier was wide-ranging and he was a proponent of the heat theory called caloric theory. He performed meticulous chemical studies which involved careful documentation of both the products and the reactants of various chemical processes. This careful analysis of products and reactants was a rarity during his times.

Lavoisier was especially interested in the chemistry of burning and played a major role in the discovery of oxygen. He also contributed to the role of oxygen in combustion and oxidation reactions such as rusting. In this work, Lavoisier espoused his caloric theory, which described heat as a massless fluid, a fluid that could flow from one object to another.

Learn more about the ordered universe.

Rival Theories of Heat

There was disagreement from other scholars. These scholars saw heat as a manifestation of motion at the atomic scale and, thus, they thought of heat as a mechanical property of matter.

It was the opportunistic American-born inventor Benjamin Thompson (Count Rumford) who ultimately resolved the debate. And finally, when Sir Humphry Davy conducted experiments, the caloric theory was buried forever.

This is a transcript from the video series The Joy of Science. Watch it now, on Wondrium.

Contributions of Count Rumford

A drawing of Count Rumford.
Count Rumford was an American inventor who resolved the debate on caloric theory. (Image: Morphart Creation/Shutterstock)

Count Rumford was always fascinated by the phenomenon of heat. He conducted numerous experiments and made inventions to improve the use of heat in everyday life. During his appointment as the commandant of police in Bavaria, he supervised the construction of a cannon.

A mold of brass was poured and the bore of the cannon was drilled out. The process of taking a huge drill, turning the barrel of the cannon, and keeping the drill bit fixed was a cacophonous process and resulted in lots of heat.

Rumford observed that with an extremely dull drill bit, nothing was drilled yet maximum amount of heat was generated. The activity helped Rumford realize that the heat was generated by the mechanical action of friction.

Learn more about the second law of thermodynamics.

Sir Humphry Davy and His Contributions to Heat Theories

English chemist Humphry Davy was born in 1778 to a middle-class family in Penzance on the coast of Cornwall. He was a highly educated man and drawn to poetry and literature.

A vintage engraved image of Sir Humphry Davy
Sir Humphry Davy debunked the caloric theory of heat. (Image: Morphart Creation/Shutterstock)

Davy also loved nature and mineral collecting. The untimely death of his father in 1794 forced Davy to take up the apothecary trade, which led to his more formal exposure to chemistry.

Davy set up his own modest laboratory to perform chemical research. He succeeded in melting ice on a cold winter day in London, just by rubbing two pieces of ice together. The caloric theory of heat was buried forever with this experiment.

Davy’s book Researches: Chemical and Philosophical gained quite widespread attention after its publication in 1800. Based on this study, Benjamin Thompson, that is Count Rumford, invited Davy to become a lecturer on chemistry at the Royal Institution of Great Britain.

Flair for Public Demonstrations

Sir Humphry Davy developed a flair for public demonstrations. On a cold icy day in London, he showed that ice could be melted by simply applying friction, contributing further to the rival theories of heat.

Yet another convincing demonstration that heat was a form of energy was provided by heating water in a closed cylinder with a piston. When water started heating, it boiled and expanded. The formation of steam raised the weight against the force of gravity and exerted a force over distance. This demonstrated heat as a form of energy, adding to the perspective on heat theories.

Common Questions about Theories of Heat

Q: What does the word thermodynamics mean?

Thermodynamics is the study of heat in motion or how heat moves.

Q: How was heat defined according to Lavoisier’s caloric theory?

Lavoisier’s caloric theory described heat as a massless fluid, a fluid that could flow from one object to another.

Q: Which book did Sir Humphry Davy write?

Sir Humphry Davy wrote a book titled Researches: Chemical and Philosophical.

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