Talk:Mpemba effect

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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)

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)

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)

External links modified (February 2018)

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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)

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)

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. 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)