In many circumstances, in the real world, systems aren't "closed" in any meaningful sense. So, when I burn a log in a fireplace, I can use words to artificially set up a kind of "log universe" that initially consists of nothing but log and some oxygen, and later consists of ashes and smoke and the air that that smoke is mixed with (which probably we should add back into our initial system) etc etc. However, it seems like a lot of wordplay when I just want to indicate that the burning log is somehow causing entropy to increase in its immediate vicinity more than the un-burning log would have. So, succinctly: "Burning a log creates entropy." or "Burning a log increases entropy." Is this the appropriate phrasing? How do I succinctly but still correctly and understandably talk about processes that "create" entropy?

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    $\begingroup$ Increase is a better word. Entropy is a quantity. You cannot create a quantity out of nowhere. Think of creating mass (which implies from nothing) vs. increasing the mass of a liquid by adding more water in a pan. Increasing the mass still sounds better. I will not create meters if we stretch an elastic band and measure its new length. $\endgroup$
    – AChem
    Feb 2, 2023 at 1:08
  • $\begingroup$ @AChem so "Burning a log increases entropy." is comprehensible, and would generally elicit a "more-or-less, sure" from scientists? $\endgroup$
    – Him
    Feb 2, 2023 at 1:22
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    $\begingroup$ I am not a nativer English speaker but "creating entropy" sounds awkward to me, although people might understand the meaning. Serious readers may not like it. Note the non-sense of order-disorder version of entropy in general chemistry and plenty of webpages, yes, there we created order and disorder, if entropy were disorder. This confusion arose because of mixing the concept of (information) entropy with Clausius' entropy. Many textbooks have corrected this notion due to one man's efforts, Dr. Frank L. Lambert. See his articles in the Journal of Chemical Education. $\endgroup$
    – AChem
    Feb 2, 2023 at 1:36
  • $\begingroup$ Entropy like temperature cannot be created but can be increased. $\endgroup$
    – Poutnik
    Feb 2, 2023 at 13:21

1 Answer 1


"Generate" or "create" are commonly encountered verbs in popular usage and in a technical context. What makes their use acceptable is that the entropy of system plus surroundings remains constant in reversible processes but increases in irreversible ones, whereas energy is always conserved and therefore constant (see for instance this post in Physics SE about the non-conservative nature of entropy). In a reversible process the entropy change of the system equals the opposite of the change in entropy of the surroundings. This is often described as entropy being "exchanged". When the entropy does not remain constant it can be said that it is "generated". Those terms should be interpreted with caution since they don't have an identical meaning to their common use. There is for instance no material substance that is being exchanged or created.

Exergonic is an adjective that describes a process carried out at constant T that results in a reduction in free energy and therefore an increase in total entropy for system plus surroundings. The term is used mainly in engineering circles and among thermodynamicists. The combustion of a log in a fireplace is an exergonic process.

Another related and relatively new concept is "entransy", see for instance Wu and Guo (2014). As explained by Kostic (2017):

The concept of new physical quantity, entransy G, represents functional-product of transferred or stored heat (Q or Q vh) as heat or ‘thermal charge’ and absolute temperature as intensive thermal potential (T), the way electrical energy represents functional product of transferred or stored ‘electrical charge’ and voltage as intensive electrical potential. The analogy is complete for ‘pure heat transfer’ without any work conversion or dissipation, referred here as ‘caloric processes’, where thermal heat is conserved, as is electrical charge, while both are degraded to lower respective potentials

However this is a new and potentially controversial concept used by some specialists, and I can't comment on how accepted it is.


(1) Wu, J.; Guo, Z. Entropy and Its Correlations with Other Related Quantities. Entropy 2014, 16 (2), 1089–1100. https://doi.org/10.3390/e16021089.

(2) Kostic, M. M. Entransy Concept and Controversies: A Critical Perspective within Elusive Thermal Landscape. International Journal of Heat and Mass Transfer 2017, 115, 340–346. https://doi.org/10.1016/j.ijheatmasstransfer.2017.07.059.


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