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Article

Which Physical Quantity Deserves the Name “Quantity of Heat”?

Karlsruhe Institute of Technology, 76128 Karlsruhe, Germany
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Academic Editor: Armin Feldhoff
Entropy 2021, 23(8), 1078; https://doi.org/10.3390/e23081078
Received: 23 June 2021 / Revised: 10 August 2021 / Accepted: 14 August 2021 / Published: 19 August 2021
(This article belongs to the Special Issue Nature of Entropy and Its Direct Metrology)
“What is heat?” was the title of a 1954 article by Freeman J. Dyson, published in Scientific American. Apparently, it was appropriate to ask this question at that time. The answer is given in the very first sentence of the article: heat is disordered energy. We will ask the same question again, but with a different expectation for its answer. Let us imagine that all the thermodynamic knowledge is already available: both the theory of phenomenological thermodynamics and that of statistical thermodynamics, including quantum statistics, but that the term “heat” has not yet been attributed to any of the variables of the theory. With the question “What is heat?” we now mean: which of the physical quantities deserves this name? There are several candidates: the quantities Q, H, Etherm and S. We can then formulate a desideratum, or a profile: What properties should such a measure of the quantity or amount of heat ideally have? Then, we evaluate all the candidates for their suitability. It turns out that the winner is the quantity S, which we know by the name of entropy. In the second part of the paper, we examine why entropy has not succeeded in establishing itself as a measure for the amount of heat, and we show that there is a real chance today to make up for what was missed. View Full-Text
Keywords: heat; balance equation for heat; entropy as heat; enthalpy; thermal energy; caloric heat; balance equation for heat; entropy as heat; enthalpy; thermal energy; caloric
MDPI and ACS Style

Herrmann, F.; Pohlig, M. Which Physical Quantity Deserves the Name “Quantity of Heat”? Entropy 2021, 23, 1078. https://doi.org/10.3390/e23081078

AMA Style

Herrmann F, Pohlig M. Which Physical Quantity Deserves the Name “Quantity of Heat”? Entropy. 2021; 23(8):1078. https://doi.org/10.3390/e23081078

Chicago/Turabian Style

Herrmann, Friedrich, and Michael Pohlig. 2021. "Which Physical Quantity Deserves the Name “Quantity of Heat”?" Entropy 23, no. 8: 1078. https://doi.org/10.3390/e23081078

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