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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.
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)
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)
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)
"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)
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)
Batholomeo or Bartholomeo ? — Preceding unsigned comment added by 188.238.242.155 ( talk) 16:49, 18 December 2016 (UTC)
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)
How mpemba effect operates
Nkungwej ( talk) 14:52, 24 August 2017 (UTC)
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.
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)
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)
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)
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)
This
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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)
This
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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)
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)
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)
In the Commons there are some uncategorized images related to this effect? These images are:
-- 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)
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)
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" [1] Another experimental paper concludes that the effect can entirely be explained by nucleation and supercooling (d) [2]. 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)
References
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)
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
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)
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.
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)
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)
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)
Thermal conductivity
References
{{
cite journal}}
: Cite journal requires |journal=
(
help)
The topic is poorly defined. What do you mean «in some circumstances it can happen»? Until the circumstances are properly described, theres no substance to be dicussed. The lack of rigorous description of the experiment that produces this observation it is meaningless to say «all other factors constant».
and this is just the very first step of desribing what would be descussed. Then come the reference to aristotle and others, while theres still nothing clarified. at best this would be a fun paradox for teaching physics, if it were described to any level. But it isnt. In its current form its pseudoscience that is not even wrong, just waste of time.
to be clear, this isnt the fault of the schoolboy who made the first observation. But neither is his obaervation amount to a “physics effect”, instead it is an effect in the sensationalist journalism reporting sense. the first perspn who reported it should have made a better job, but that is also not to find a fault with the reporter. Reporters are not expected to only make scientifically meaningful statements.
this shifts the burden to the next in line, which is wikipedia: this article should either give a scientifically rigorous description of the effect, that is refer to a publication where these details are included, or begin the lede with a clear statement that no such experiment is to be found and therefore refer the topic to the heresay, beer science, word-play category which may say that there is a hitherto unexplayed phenomena but, fails to describe the phenomena in a way that would be the prerequisite of any methodological inquiry into its explanation. 2A02:2121:62B:5A3C:94B8:62C4:138E:62A4 ( talk) 10:43, 26 May 2024 (UTC).
A has said a great many things on many topics, but ref.3. gives no account as to what relevant statement A has made and how that relates to the alleged observation. This reference is of as much use as another reference to what Puss in Boots has said would have been. 2A02:2121:62B:5A3C:94B8:62C4:138E:62A4 ( talk) 10:53, 26 May 2024 (UTC).
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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.
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)
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)
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)
"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)
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)
Batholomeo or Bartholomeo ? — Preceding unsigned comment added by 188.238.242.155 ( talk) 16:49, 18 December 2016 (UTC)
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)
How mpemba effect operates
Nkungwej ( talk) 14:52, 24 August 2017 (UTC)
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.
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)
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)
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)
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)
This
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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)
This
edit request has been answered. Set the |answered= or |ans= parameter to no to reactivate your request. |
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)
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)
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)
In the Commons there are some uncategorized images related to this effect? These images are:
-- 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)
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)
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" [1] Another experimental paper concludes that the effect can entirely be explained by nucleation and supercooling (d) [2]. 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)
References
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)
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
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)
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.
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)
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)
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)
Thermal conductivity
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The topic is poorly defined. What do you mean «in some circumstances it can happen»? Until the circumstances are properly described, theres no substance to be dicussed. The lack of rigorous description of the experiment that produces this observation it is meaningless to say «all other factors constant».
and this is just the very first step of desribing what would be descussed. Then come the reference to aristotle and others, while theres still nothing clarified. at best this would be a fun paradox for teaching physics, if it were described to any level. But it isnt. In its current form its pseudoscience that is not even wrong, just waste of time.
to be clear, this isnt the fault of the schoolboy who made the first observation. But neither is his obaervation amount to a “physics effect”, instead it is an effect in the sensationalist journalism reporting sense. the first perspn who reported it should have made a better job, but that is also not to find a fault with the reporter. Reporters are not expected to only make scientifically meaningful statements.
this shifts the burden to the next in line, which is wikipedia: this article should either give a scientifically rigorous description of the effect, that is refer to a publication where these details are included, or begin the lede with a clear statement that no such experiment is to be found and therefore refer the topic to the heresay, beer science, word-play category which may say that there is a hitherto unexplayed phenomena but, fails to describe the phenomena in a way that would be the prerequisite of any methodological inquiry into its explanation. 2A02:2121:62B:5A3C:94B8:62C4:138E:62A4 ( talk) 10:43, 26 May 2024 (UTC).
A has said a great many things on many topics, but ref.3. gives no account as to what relevant statement A has made and how that relates to the alleged observation. This reference is of as much use as another reference to what Puss in Boots has said would have been. 2A02:2121:62B:5A3C:94B8:62C4:138E:62A4 ( talk) 10:53, 26 May 2024 (UTC).