Talk:Mpemba effect

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Wording

The second paragraph says "common knowledge according to Aristotle during his time", but that's not my understanding of what Aristotle said "the water has previously been warmed". Water that has previously been warmed is not the same as water that is warm now.

Took another stab at top-line wording. The effect is an observation (valid or not) of comparisons, not some set of incidences, examples, or occasions.

Diagram

I've added a relevant diagram (already available on Wikimedia Commons), and also expanded the Historical section a little, discussing the work of James Black. I know that this has been a contentious topic in the past, but I thought that it was worth gently revisiting; I've tried to be cautious, but might reasonably be accused of over-interpreting Farenheit's contributions in the light of subsequent knowledge; I'm also rather relying on Black's description of Farenheit's work, as my Latin isn't up to scratch. Cluebot archiving removed so that we can have a chat! Klbrain (talk) 12:04, 17 August 2015 (UTC)

This diagram needs to be removed as its clearly a faulty experiment. At equal temperatures before freezing the rate of temperature decline should be the same -they are not and so it is clear that the hot sample is actually being cooled more quickly. — Preceding unsigned comment added by 2A02:C7D:86E:7200:A0E1:F55A:6070:B475 (talk) 15:29, 23 June 2019 (UTC)

I have remove the diagram because it fails to meet Wikipedia’s standards for reliability, specifically because it is only a self-published source. The fact that it comes from a commercially self-promoting website makes it further suspect.

Also (as noted elsewhere on this page) the removed diagram is suspect because it purports to show water freezing at 2-3 degrees, not zero.

Worse, the diagram shows the colder water freezing first! Freezing is where the flat part happens. Whether one sample or the other fell below some lower point (reported as “zero”) has no bearing on freezing, or, therefor, on the Mpemba effect. — Preceding unsigned comment added by Slgaiser (talk • contribs) 02:47, 4 November 2021 (UTC)

Note this section is not about the current image, but rather about File:Mpemba-simple.svg, which is no longer in the article.

As for the image currently in this article, the flat part indicates where the phase transition is occurring, and freezing isn't complete until the flat part ends. The cold water starts its phase transition first, but the hot water completes its phase transition sooner while the cold water isn't yet fully frozen. ~Anachronist (talk) 05:35, 4 November 2021 (UTC)

Quite right. I stand corrected.Slgaiser (talk) 18:49, 6 November 2021 (UTC)

Unbelivable: The image (https://www.picotech.com/library/results/freezing-hot-cold-water) must shame anyone who has seen this topic - since 2010! Especially the originator, who sell measurement equipment. Water freezes at 0°C! I swapped the image for one from "Mpemba Effect Demystified" https://doi.org/10.31224/osf.io/3ejnh.Freezer18 (talk) 13:26, 19 January 2022 (UTC)

@Freezer18: Thanks, that's a way better image. However, are you sure of the license? You uploaded that as a public domain dedication, but I see no indication in the source material that it's public domain. If the copyright holder has not released it, then the image will be deleted, we can't use it, and the horrible previous image would be restored. ~Anachronist (talk) 23:15, 19 January 2022 (UTC)

It's taken form a preprint, link above, it's CC0=public domainFreezer18 (talk) 19:41, 20 January 2022 (UTC)

No one seems to mention freezer thermostat as a possible cause

If you put something hot into a freezer it will switch the thermostat to turn the freezer on. This will cause the temperature inside the freezer to drop and so cause the water to turn to ice more quickly. There is hysteresis on these thermostats so they will reduce the temperature in the freezer to a lower temperature than the set temperature. To do a controlled test you would need to put the hot water ice cube trays cold ones in the same freezer at the same time. Why hasn't someone done this with a camera lens inside the freezer to monitor exactly when each one turns to ice? — Preceding unsigned comment added by Caparn (talk • contribs) 16:49, 9 May 2016 (UTC)

I would be WP:BOLD and do it myself but I'm not certain I could avoid doing so in a manner that would amount to original research. But if a youtube video from someone whose credentials consist of "some college" can be cited I'll go for it. Mattman00000 (talk) 13:01, 23 June 2016 (UTC)

Bullseye @Caparn. It is comfirmed that most of the reproduction are wrong if they don't put sample together into the freezer to deal with the thermostat control variance. I bet many "scientist" dare to admit that such simple blunders. This is the nih.gov experiment : Questioning the Mpemba effect: hot water does not cool more quickly than cold . This whole wiki page must include this "simple" finding.

I am pretty sure that many people have demonstrated the effect using outdoor as the "freezer". Don't forget, North Dakota is basically Siberia with family restaurants. --Guy Macon (talk) 17:31, 9 February 2019 (UTC)

interesting temperature

"containers at 35 and 5 °C (95 and 41 °F) to maximize the effect"

This 5 °C is roughly (as if rounded) where liquid water is at maximum density. Freezing from the higher temperature would require less expansion. The density change should also have an effect on entropy. — Preceding unsigned comment added by 97.104.88.146 (talk) 08:26, 22 May 2016 (UTC)

What is 'quantity'?

The article several times refers to the 'quantity' of water without specifying how this is defined. The Mpemba/Osborne experiments appear to have used volume as the measure of quantity. The other obvious measure would be mass (usually measured by weighing in standard conditions). Since the density (mass per unit volume) of water varies with temperature, the two measures are not equivalent, as a unit volume of water at a higher temperature will generally have less mass than the same volume at a lower temperature. Quantitatively the difference is probably too small to explain the alleged phenomena, but it seems desirable to avoid the ambiguity.86.132.140.164 (talk) 13:56, 7 December 2016 (UTC)

Name

Batholomeo or Bartholomeo ? — Preceding unsigned comment added by 188.238.242.155 (talk) 16:49, 18 December 2016 (UTC)

Probably with an r. For more information and external sources such as pp 7 and 11 of an FAO report see an old Wikipedia biography of Mpemba--Rumping (talk) 13:29, 16 February 2017 (UTC)

Talk archives

There are achieves of previous talk at Talk:Mpemba effect/Archives/ 1 and Talk:Mpemba effect/Archives/ 2 but I cannot see a link on these pages --Rumping (talk) 13:29, 16 February 2017 (UTC)

Added this in manually at the top of the talk page, as the usual template wasn't working with the non-standard archive naming (in the past)

Resolved

Klbrain (talk) 16:39, 2 April 2018 (UTC)

History

How mpemba effect operates

Nkungwej (talk) 14:52, 24 August 2017 (UTC)

A personal observation.

When I was a schoolteacher, one of the experiments we did with "special needs" children was to freeze water in a watch glass to make a lens. Demonstrating that it doesn't have to be glass - even ice can make a lens. The teachers'guide suggested that we teachers use near-boiling water for this, because such water contains very few dissolved gases and results in a much "clearer" lens, because in a good quality freezer the water would freeze too quickly for air to dissolve in it.

We were surprised to discover that near-boiling water froze about as quickly as room temperature water. I have no idea whether this is related.

Graph in Article

Isn't there a mistake in the graph? When a substance is changing phase, the temperature of the substances remains constant. In the graph, both the initially hot and initially cold water both show a constant temp, but it's not 0 C!!! Shouldn't that graph be removed? — Preceding unsigned comment added by 207.255.29.67 (talk) 03:36, 27 December 2017 (UTC)

It doesn't rather suggest that their temperature probe hadn't been properly zero'ed, but I think that the graph is still useful because it shows a plateau close to zero. I'd leave it in place until someone can find a better figure. Klbrain (talk) 16:42, 2 April 2018 (UTC)

Without a caption stating where the graph is sourced from, who performed the experiment, and/or under what conditions the experiment was performed, this graph is worse than useless, it is potentially misleading. It ought to be removed if it cannot be fully and properly sourced. Even then, in the future, this graph might be held up as an example of how wrong thinking used to be about the alleged Mpemba effect, which likely does not exist. Robert K S (talk) 20:45, 8 February 2019 (UTC)

I agree with Robert K S: unsourced, the graph is worse than useless. It should be removed from this article. Slgaiser (talk) 00:04, 13 June 2021 (UTC)

I disagree. The graph is a useful illustration of the concept. It doesn't need to be exactly correct to serve as an illustration. The graph is likely a measurement from a personal experiment. See WP:OI: this is policy. Original images created by Wikipedians (as this one is) are not considered original research.

There are similar graphs published in refereed journals (figure 7 in this paper, for example). But we couldn't use any published graph due to copyright restrictions, unless the copyright holder released the graphic under an acceptable free license. A similar graph generated by a Wikipedian serves the illustrative purpose just as well. ~Anachronist (talk) 05:57, 4 November 2021 (UTC)

Thermal eddy momentum and diffusivity via Turbulent Prandtl number?

This is just an armchair observation, but wouldn't greater temperature differential and thermal gradients that are further from equilibrium be responsible for creating thermal eddies, flows and momentum in either or both fluid turbulence and thermic turbulence? With a greater momentum, we see a flywheel effect of thermal distribution even as temperatures nearer equilibrium. See Turbulent Prandtl number. - 75.173.66.142 (talk) 20:27, 1 January 2018 (UTC)

Photos

There are two photos, purporting to lend evidence to this effect. The caption on one states "Mpemba effect experiment: the hot water contained in a thermos, if thrown into the air in a very cold environment, freezes instantly before touching the ground."

This is not a very helpful caption for two reasons: 1) water cannot freeze "instantly," and 2) where's the evidence that it freezes before it hits the ground? Photos or videos of throwing hot water into very cold air show a lot of condensation, and a lot of droplets so it can look very spectacular, especially when backlit. But they never show that the droplets are frozen.

Is there evidence that the water freezes before it hits the ground?

Hermanoere (talk) 18:43, 24 October 2018 (UTC)

The two photos do not demonstrate the Mpemba Effect. As stated by the article, the Mpemba Effect relates to hot water freezing faster than cold water in certain circumstances, none of which is identified as having been thrown up in the air. Also, while the Mpemba Effect is not well understood, the trick of throwing hot water into very cold air so that it quickly vaporizes and then condenses into small droplets and freezes into a cloud of crystals is well understood. There is a good explanation of it at https://news.nationalgeographic.com/2018/01/frozen-bubbles-boiling-water-freezing-explained-bomb-cyclone-bombogenesis-winter-weather-viral-videos-spd/https://news.nationalgeographic.com/2018/01/frozen-bubbles-boiling-water-freezing-explained-bomb-cyclone-bombogenesis-winter-weather-viral-videos-spd/. Other sources across the internet also cite the Mpemba Effect for this demonstration, but this is a case of two similar-seeming effects being attributed to the same cause without reason. — Preceding unsigned comment added by MeeToney (talk • contribs) 20:18, 1 February 2019 (UTC)

Semi-protected edit request on 26 January 2019

Suggested explanations The following explanations have been proposed:

when electrons are moving faster the it is easier to form a optimal atomic orbit shape having longer time to release and gather eletro energy makes the shell thinner sharing is easier The Beautiful Captain Lightning (talk) 21:53, 26 January 2019 (UTC)

 Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format and provide a reliable source if appropriate. ‑‑ElHef (Meep?) 23:05, 26 January 2019 (UTC)

Semi-protected edit request on 1 February 2019

Please remove the two pictures of people throwing boiling water into the cold air as they do not seem to relate to the Mpemba Effect.

The Mpemba Effect relates to hot water freezing faster than cold water in certain circumstances, none of which is identified as having been thrown up in the air. Also, while the Mpemba Effect is not well understood, the trick of throwing hot water into very cold air so that it quickly vaporizes and then condenses into small droplets and freezes into a cloud of crystals is well understood. There is a good explanation of it at https://news.nationalgeographic.com/2018/01/frozen-bubbles-boiling-water-freezing-explained-bomb-cyclone-bombogenesis-winter-weather-viral-videos-spd/ https://news.nationalgeographic.com/2018/01/frozen-bubbles-boiling-water-freezing-explained-bomb-cyclone-bombogenesis-winter-weather-viral-videos-spd/. Other sources across the internet also cite the Mpemba Effect for this demonstration, but this is a case of two similar-seeming effects being attributed to the same cause without reason. thanks! MeeToney (talk) 20:36, 1 February 2019 (UTC)

 Done – Jonesey95 (talk) 05:34, 2 February 2019 (UTC)

Unique to water?

Is there any information documenting whether this supposed affect has been tested with other liquids? Watching the BBC Facebook video brought me here; they claimed that this is one of the unique properties of water alone. RobP (talk) 14:10, 9 February 2019 (UTC)

We know that it works for ice cream. Mpemba was a Tanzanian student who noticed that hot ice cream mix freezes faster than cold ice cream. But of course ice cream contains water. I did a google search to see if anyone had tried it with wax, oil, iron, aluminum, etc. but didn't find anything. If it turns out that the the Mpemba effect works with iron, that would be the death of the hydrogen-oxygen bond theory. --Guy Macon (talk) 17:41, 9 February 2019 (UTC)

It has been reported to work for ice cream. Are there any reliable sources stating that it has been measured for ice cream? · · · Peter Southwood ^(talk): 07:21, 28 January 2021 (UTC)

O:H-O Bond Anomalous Relaxation Resolving Mpemba Paradox (2013)

To consider integrating:

Why Hot Water Freezes Faster Than Cold—Physicists Solve the Mpemba Effect

O:H-O Bond Anomalous Relaxation Resolving Mpemba Paradox

Peter Kaminski (talk) 17:10, 8 May 2019 (UTC)

Photos 2

In the Commons there are some uncategorized images related to this effect? These images are:

• File:Mpemba-3182934 1280.jpg
• File:Mpemba effect (30653381280).jpg
• File:Mpemba-3138995 1280.jpg

--Estopedist1 (talk) 06:44, 6 October 2019 (UTC)

in addition: File:Sky-3181008 1280.jpg and File:Sky-31810071280.jpg--Estopedist1 (talk) 07:32, 11 October 2019 (UTC)

Pretty pictures but no evidence that they are relevant. · · · Peter Southwood ^(talk): 07:16, 28 January 2021 (UTC)

Is Mpemba a 'scientist'?

I've edited the page to change Mpemba's appellation from 'scientist' to 'schoolboy'. I hope that's not too controversial! Yes, he was a 'scientist' in the amateur sense, publishing an observation on science; but he was never a professional scientist, did not gain a degree in science, and spent his adult life as a game warden. And it's probably of more relevance and interest to the reader that he was a schoolboy when he made his observation.

Drjamesaustin (talk) 22:50, 18 July 2020 (UTC)

Theoretical evidence should be given low priority

The article makes a claim about an experimental observation: hot water freezes faster than cold water (in certain circumstances). However in the literature there is a lot of discussion about the validity of this experimental observation and its poor reproducibility. Most careful experimental work conclude that the effect is due to confounding factors such as (quoting) " (a) evaporation, (b) dissolved gases, (c) mixing by convective currents, and (d) supercooling" Another experimental paper concludes that the effect can entirely be explained by nucleation and supercooling (d) . These factors are already mentioned in the article, however against this high quality experimental evidence theoretical evidence for the Mpemba effect is brought. However these theoretical papers atre highly idealized and can not prove in any way that this effect occurs in water (or any liquid at all). Ofcourse they open interesting avenues for realizing the Mpemba-like effects, and speculate about potential mechanisms driving it, but they do not lend credibility to the Mpemba effect actually occuring. I propose moving all theoretical references to their own section. I want to stress that I make no statements about the quality of the theoretical work, just stating that theoretical evidence in general is much weaker than experimental evidence.Nomenenus nescio (talk) 07:59, 16 October 2020 (UTC)

I went ahead and split experiments and theory in their own separate sections. Content and wording is left wholly intact. Nomenenus nescio (talk) 08:30, 19 October 2020 (UTC)

References

Urban Myth?

Having looked at some of the references here, I can see little evidence that this effect is reproducible and has any scientific validity rather than being an urban myth.

Are there any clear descriptions of how the effect can be reliably created in water? Belinda479 (talk) 10:35, 7 November 2020 (UTC)

• It appears to be sensitive to initial conditions favouring significant supercooling. · · · Peter Southwood ^(talk): 07:07, 28 January 2021 (UTC)
• In a word, ‘no’. There are no clear descriptions because it cannot be reliably created. And while it may be sensitive to initial conditions, it may also be sensitive to so-called hidden variables, or even to supernatural intervention. My (admittedly limited) reading of the literature strongly suggests the effect is nonexistent, attributable to measurement errors. Indeed, there seems to be much more research into explaining the so-called effect than in actually demonstrating it. Slgaiser (talk) 23:54, 12 June 2021 (UTC)
• Frankly, it seems so absurd on its face that I'm surprised the article treats it with as much deference as it does. If this were true, it would lead to some absurd results. Consider putting equal volumes of 100 degree C water into two beakers, putting the first in one freezer and the second on the kitchen counter, and then waiting for 1 hour. At this point, the water that is in the first beaker will be considerably colder than that in the second. Then put the second beaker in a second freezer -- if this theory were true, then the second beaker would freeze faster. And if, at the same time, you put a third beaker, this one with 100 degree water, into a third freezer, it would freeze faster than the second beaker, and therefore faster than the first -- but this is an absurdity: how could the third beaker, which was placed in its freezer at the same temperature that the first beaker was when it was placed in its freezer an hour before, freeze before the first beaker? -Waidawut (talk) 03:31, 14 July 2021 (UTC)

Fluid dynamics and thermodynamics are not uncommonly counterintuitive. It's a bit burried in the current version of the article, but in my view, the best theoretical explanation is from 2021. To quote from the abstract of that paper, This theory is shown to be consistent with analysis of observations of freezing times measured by Mpemba and Osborne. My point here is that simple thought experiments aren't sufficient to refute experimental findings observing such an effect, as more sophisticated theory is consistent with the Mpemba effect. I do agree, though, that it would be nice to have more experimental evidence? A challenge to any applied physicists out there? Klbrain (talk) 20:01, 15 July 2021 (UTC)

References

Phlogiston

Having read the references, I’m in the camp that the Mpemba effect is bogus, pseudo science. Or call it “Urban Myth”. Or maybe it’s real. Regardless, I added this possible theory mostly as a joke. I understand that this is inconsistent with the guidelines for Wikipedia, and accordingly invite its removal.

That said, I also wrote it hoping that readers might follow the phlogiston link, learn about it, and consider the evolution from today’s credible theories to yesterday’s debunked ones.

At least combustion is real.  ;-)

Slgaiser (talk) 23:23, 12 June 2021 (UTC)

Not at all amusing; fortunately, someone quickly reversed your unconstructive edits. Klbrain (talk) 14:38, 22 August 2021 (UTC)

Resolved

I’m glad my misuse was quickly corrected. I will henceforth refrain. Perhaps my good intentions will reap benefits for some few who read this talk page.

Graph in lead

The lead says that "this so-called “effect” is not reproducible" then has a graph reproducing it, showing hot water reaching zero before cold water. Should the graph be there, or is the sentence incorrect? --Lord Belbury (talk) 15:41, 18 August 2021 (UTC)

The sentence, using the pejorative "so-called" and scare quotes around "effect" is definitely not neutral, and doesn't reflect what the cited source actually says. I have modified the sentence. ~Anachronist (talk) 18:43, 22 August 2021 (UTC)

Diagram as the lead image

Anyone can create a personal web page, self-publish a book, or claim to be an expert. That is why self-published material such as books, patents, newsletters, personal websites, open wikis, personal or group blogs (as distinguished from newsblogs, above), content farms, Internet forum postings, and social media postings are largely not acceptable as sources — Preceding unsigned comment added by Slgaiser (talk • contribs) 04:07, 4 November 2021 (UTC)

@Slgaiser: Please familiarize yourself with Wikipedia policy. WP:OI in particular. ~Anachronist (talk) 05:28, 4 November 2021 (UTC)

The following comments are about the image file File:Mpemba-two-water-probes.svg, currently at the top of the page (but soon to be removed again). The data shown in that image come from the web site picotech.com, a seller of temperature measuring and data logging devices. (See the link under External Sites.). The image clearly fails WP’s verifiability standards (see WP:VERIFY) for two reasons.

First, my previously stated objection to the above image file is that it presents data that do not meet Wikipedia’s standards for verifiability, specifically because those data have only been self-published by a non-expert (see WP:SELFPUB). And while the discussion has revolved around a specific image file, this discussion is fundamentally not about the image itself, but rather is about the inclusion or exclusion of information, in this case Picotech’s self-published temperature measurements. And so WP:SPS logically applies not just to the image in question, but also to any other tabulation, plot, or other representation of Picotech’s data.

I now add a second objection, to be considered separately, that the data under discussion do not meet verifiably standards because they represent original research. The injunction in WP:NOR is explicit: “Wikipedia articles must not contain original research”. I assert that Picotech’s experiment (and results) are self-evidently original research, precluding them entirely. Again, this refers to the research itself, the data, in whatever form, plotted, tabulated, or otherwise. It’s difficult to conceive of any reasonable definition of “original research” which does not include the results of Picotech’s private experiments, “unpublished” as WP uses the term.

Having familiarized myself with WP:OI, I find nothing of relevance, except perhaps “Original images created by a Wikipedian are not considered original research…”, with exceptions. Surely it is not intended that Original Images are some sort of “magic verifiability wrapper” (my term)? Not intended that an Original Image of unverifiable original research somehow becomes verifiable? That an Original Image of unverifiable self-published material becomes verifiable? Or that an Original Image of a screenshot of an unverifiable blog is itself verifiable? I hope I misunderstand.

As an afterthought, I speculate that had the data shown come from a verifiable source (peer reviewed, or self-published by an expert), that there would be some discussion of why the samples seem to freeze at three degrees instead of at zero, and why there is an odd step in each sample’s temperature around six degrees, and why neither sample appears to have supercooled. And would better describe the experimental setup, and would say something about repeatability. Those hallmarks will likely be present in most [modern] reliable, verifiable sources. Slgaiser (talk) 18:49, 6 November 2021 (UTC)

@Slgaiser: To answer your objections:

The image meets standards of verifiability under WP:OI because anyone can replicate the experiment and, if the conditions are correct, obtain a similar graph.

The fact that the image was created by a seller of temperature probes is irrelevant. It would not be in their interest to falsify information. This is clearly the result of an experiment demonstrating their probes. So what? The graphic itself is not an attempt to advertise or sell anything. An objection based on the identity of the creator is invalid on its face.

Data published by non-experts, as a result of experiment, is acceptable under WP:OI, which clearly states "Original images created by a Wikipedian are not considered original research, so long as they do not illustrate or introduce unpublished ideas or arguments." This diagram does not illustrate or introduce an unpublished idea or argument. It illustrates a previously published idea/argument. That is acceptable.

You even acknowledge yourself that the graph wasn't made available by some noob fooling around at home, but by a maker of temperature probes, who clearly must know something about measuring temperature, and therefore must have some expertise. You have no knowledge about the credentials behind the designer of the probes or the person who conducted the experiment. But that doesn't matter, according to WP:OI.

The image may simply be the result of a student experiment. So what? A result is a result. The article clearly states that it is not easy to reproduce. If an example can be found, released under an acceptable free license, illustrating the result, then it serves as a good illustration for this article.

You can find similar graphs in scholarly journals on Google Scholar. Figure 7 in this article is one example. We cannot use it though, because of copyright. The fact that such images exist doesn't mean we must use them instead. We can't without a release from the copyright holder. Therefore, we use images generated by non-experts instead.

That there are anomalies in the graph simply illustrate possible problems with the experimental setup. I have no doubt that this graph is the result of an actual, but flawed, experiment. And the article discusses the possibility that all these Mpemba effect experiments are flawed. That is not a reason to remove the image.

Instead of removing it, the caption should be improved. I have added a caption, and invite you to improve on it. ~Anachronist (talk) 19:07, 6 November 2021 (UTC)

Suggested explanations

Thermal conductivity

1. Criticism of §1: ME also arises (sometimes) outdoors, on block or pot of ice.
   On a dry, clean cooler surface, i.e. ice thickness ~0, and not flat bottom of the cup, bottom conductance is usually poor. (According to )
2. Compelling proposal, if you read more then abstract. Until reviewed by others added as "Suggested explanation".

References