# Hot water makes ice cubes freeze quicker? **URL:** \ **Category:** Factual Questions\ **Created:** [May 13, 2006, 5:48pm UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662 "2006-05-13T17:48:34Z")\ **Posts on this page:** 19\ **Page:** 4
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [November 2, 2013, 4:18pm UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/61 "2013-11-02T16:18:48Z")
Mpemba effect or not, I stand by my statement in post #16 (slightly modified here): > [@](#): > > Consider this: If two identical samples _differing only in their initial temperature_ are cooled by the same amount of heat extraction for each and are started at the same time, at some point in time the originally hotter sample must exactly match the current temp of the originally cooler sample. At that instant, unless you postulate that the substance has some kind of memory about past events, they become identical in every way. If the originally hotter one subsequently reaches freezing sooner than the other, something paranormal is going on here. The Mpemba doc throws all kinds of additional factors into the equation like air bubbles, dissolved solids, added impurities, air flow over the surface etc., any of which could cause cooling to be slower or faster, _but this is changing the premise,_ which is concerned _only_ with unadulterated water, not water _with_ something. ---
**Author:** ![The\_Librarian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/the_librarian/32/402_2.png) [@The\_Librarian](https://boards.straightdope.com/u/The_Librarian)\ **Post date:** [November 2, 2013, 5:04pm UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/62 "2013-11-02T17:04:36Z")
Out of interest: at what volume/shape/temperature should I be expecting a freezing time where the warm water comes anywhere near close? Or: describe an experiment to falsify my assertion. Experiments I’ve done so far: Two shot glasses 7 degree C./45 degree C. Freezer @ -20 C. Result: cold water is frozen solid before ice starts to form in the warm water. Two plastic cups: 7 C /95C, freezer @ -20 C. Result: see above. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [November 2, 2013, 5:27pm UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/63 "2013-11-02T17:27:09Z")
The [winner’s explanation of the Mpemba Effect](http://www.rsc.org/mpemba-competition/mpemba-winner.asp) is very good. [http://www.rsc.org/mpemba-competition/](http://www.rsc.org/mpemba-competition/) > [@](#): > > The Royal Society of Chemistry offered £1000 to the person or team producing the best and most creative explanation of the phenomenon by which hot water sometimes freezes faster than cold water, known today as The Mpemba Effect, and 22 000 of you responded. ---
**Author:** ![jtur88](https://avatars.discourse-cdn.com/v4/letter/j/e9c0ed/32.png) [@jtur88](https://boards.straightdope.com/u/jtur88)\ **Post date:** [November 2, 2013, 6:13pm UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/64 "2013-11-02T18:13:59Z")
By the way, does anybody have any details about how Archimedes made ice cubes while performing this experiment? Was he using a frost-free refrigerator, or one of the older models that did not regulate humidity in the freezer? ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [November 3, 2013, 1:28am UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/65 "2013-11-03T01:28:25Z")
> [@jtur88](#): > > By the way, does anybody have any details about how Archimedes made ice cubes while performing this experiment? Was he using a frost-free refrigerator, or one of the older models that did not regulate humidity in the freezer? I think you mean Aristotle, not Archimedes. Here’s what he says: > [@](#): > > “The fact that the water has previously been warmed contributes to its freezing quickly: for so it cools sooner. Hence many people, when they want to cool water quickly, begin by putting it in the sun. So the inhabitants of Pontus when they encamp on the ice to fish (they cut a hole in the ice and then fish) pour warm water round their reeds that it may freeze the quicker, for they use the ice like lead to fix the reeds.” > Meteorology I.12 348b31–349a4 Were you not aware that water can be frozen other than by refrigerators, such as by cold weather?:dubious: ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [November 3, 2013, 1:50am UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/66 "2013-11-03T01:50:27Z")
> [@Musicat](#): > > Mpemba effect or not, I stand by my statement in post #16 (slightly modified here): > > > [@](#): > > > > Consider this: If two identical samples differing only in their initial temperature are cooled by the same amount of heat extraction for each and are started at the same time, at some point in time the originally hotter sample must exactly match the current temp of the originally cooler sample. At that instant, unless you postulate that the substance has some kind of memory about past events, they become identical in every way. If the originally hotter one subsequently reaches freezing sooner than the other, something paranormal is going on here. > > The Mpemba doc throws all kinds of additional factors into the equation like air bubbles, dissolved solids, added impurities, air flow over the surface etc., any of which could cause cooling to be slower or faster, _but this is changing the premise,_ which is concerned _only_ with unadulterated water, not water _with_ something. The article on the Mpemba effect linked above specifically addresses this. Even with unadulterated water, as the linked article points out, your reasoning rests on the assumption that “average temperature of the water” is the only important factor here. They might **not** become identical in every way. ETA: We’ve had Straight Dope columns using computational fluid dynamics software to solve the [shower curtain mystery](http://www.straightdope.com/columns/read/1369/why-does-the-shower-curtain-blow-in-despite-the-water-pushing-it-out-revisited) and the [Guinness Stout bubbles question](http://www.straightdope.com/columns/read/1368/why-do-the-bubbles-in-guinness-stout-float-down). Can somebody apply computational fluid software to this problem and see if any of the “convection currents” effects show up? ---
**Author:** ![The\_Librarian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/the_librarian/32/402_2.png) [@The\_Librarian](https://boards.straightdope.com/u/The_Librarian)\ **Post date:** [November 3, 2013, 3:18am UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/67 "2013-11-03T03:18:30Z")
> [@The\_Librarian](#): > > Out of interest: at what volume/shape/temperature should I be expecting a freezing time where the warm water comes anywhere near close? > > Or: describe an experiment to falsify my assertion. > > Experiments I’ve done so far: > > Two shot glasses 7 degree C./45 degree C. Freezer @ -20 C. Result: cold water is frozen solid before ice starts to form in the warm water. > > Two plastic cups: 7 C /95C, freezer @ -20 C. Result: see above. > [@chorpler](#): > > The article on the Mpemba effect linked above specifically addresses this. Even with unadulterated water, as the linked article points out, your reasoning rests on the assumption that “average temperature of the water” is the only important factor here. They might **not** become identical in every way. > > ETA: We’ve had Straight Dope columns using computational fluid dynamics software to solve the [shower curtain mystery](http://www.straightdope.com/columns/read/1369/why-does-the-shower-curtain-blow-in-despite-the-water-pushing-it-out-revisited) and the [Guinness Stout bubbles question](http://www.straightdope.com/columns/read/1368/why-do-the-bubbles-in-guinness-stout-float-down). Can somebody apply computational fluid software to this problem and see if any of the “convection currents” effects show up? What I’m missing here are concrete directions on how to duplicate the elusive RESULTS. ‘The world is more complex than you think’ is a very deep and almost universal truth but, as we say here; Cite? Don’t come back with links to wordy sites with 0 experimental data. I want to see replicatable results. I want to know how to get warmer water to freeze sooner than colder water. Because in my fridge it most definitely doesn’t. ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [November 3, 2013, 8:13am UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/68 "2013-11-03T08:13:30Z")
> [@The\_Librarian](#): > > What I’m missing here are concrete directions on how to duplicate the elusive RESULTS. > > ‘The world is more complex than you think’ is a very deep and almost universal truth but, as we say here; Cite? > > Don’t come back with links to wordy sites with 0 experimental data. > > I want to see replicatable results. I want to know how to get warmer water to freeze sooner than colder water. Because in my fridge it most definitely doesn’t. Well, if I were you, I would try one container only a few degrees hotter than the other, not 38 to 88 degrees hotter. ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [November 3, 2013, 11:32am UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/69 "2013-11-03T11:32:25Z")
> [@The\_Librarian](#): > > What I’m missing here are concrete directions on how to duplicate the elusive RESULTS. > > ‘The world is more complex than you think’ is a very deep and almost universal truth but, as we say here; Cite? > > Don’t come back with links to wordy sites with 0 experimental data. > > I want to see replicatable results. I want to know how to get warmer water to freeze sooner than colder water. Because in my fridge it most definitely doesn’t. Yeah, I’m trying to find the details of Jearl Walker’s “Amateur Scientist” column in September 1977 (the one mentioned in the Straight Dope column), because the article from the physics FAQ mentions that he gives good starting points. Unfortunately, none of my academic affiliations have access to Scientific American back beyond 1984, so I am still searching. Also for the other cited papers from the FAQ. The original Mpemba article quotes him with the following: “If you take two similar containers with equal volumes of water, one at 35 °C (95 °F) and the other at 100 °C (212 °F), and put them into a freezer, the one that started at 100 °C (212 °F) freezes first. Why?” So that might be a good starting point, although it hardly sounds to me like “cold water” vs “hot water” – more like “warm water” vs “very hot water” – but it does seem like a good place to start with an actual experiment that could be done in the home. ---
**Author:** ![The\_Librarian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/the_librarian/32/402_2.png) [@The\_Librarian](https://boards.straightdope.com/u/The_Librarian)\ **Post date:** [November 3, 2013, 11:40am UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/70 "2013-11-03T11:40:39Z")
Two (identical) plastic cups: one @ 35 C , one @ 95 C (fresh out of a boiling kettle). Just went into the freezer. ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [November 3, 2013, 11:41am UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/71 "2013-11-03T11:41:36Z")
[This paper](http://arxiv.org/abs/1003.3185) at [arXiv.org](http://arXiv.org), downloadable as a PDF at [this link](http://arxiv.org/ftp/arxiv/papers/1003/1003.3185.pdf), goes into great detail about experimental conditions that result in hot water freezing faster than cold water. ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [November 3, 2013, 11:45am UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/72 "2013-11-03T11:45:04Z")
Awesome, **The Librarian**. Science in action! Are you measuring which hits 0 °C first, or which forms ice first, or which freezes solid first? (The difficulty of measuring when something is frozen solid has stymied me so far.) ETA: I will be at the local university on Tuesday morning, so I will be scanning a copy of Jearl Walker’s column from their physical **Scientific American** archives then, if nobody can find it first. ---
**Author:** ![The\_Librarian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/the_librarian/32/402_2.png) [@The\_Librarian](https://boards.straightdope.com/u/The_Librarian)\ **Post date:** [November 3, 2013, 12:39pm UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/73 "2013-11-03T12:39:09Z")
I’m going by the easily reproduced " if I can turn it over without spilling; it’s frozen". Btw: after reading your (chorplers) link it becomes more obvious to me that mister Mpemba is full of it. The conditions needed to reliably reproduce ( according to the article ) the effect are pretty far from anything available to a Tanzanian schoolboy. Update: both cups still liquid: ---
**Author:** ![The\_Librarian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/the_librarian/32/402_2.png) [@The\_Librarian](https://boards.straightdope.com/u/The_Librarian)\ **Post date:** [November 3, 2013, 12:48pm UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/74 "2013-11-03T12:48:59Z")
Having read the whole article: I’ve also read its conclusion: all else being equal: there is no Mpemba effect. Bullshitters be Bullshitting. Update: frost has formed in the ‘cold’ cup. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [November 3, 2013, 1:16pm UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/75 "2013-11-03T13:16:48Z")
> [@chorpler](#): > > [This paper](http://arxiv.org/abs/1003.3185) at [arXiv.org](http://arXiv.org), downloadable as a PDF at [this link](http://arxiv.org/ftp/arxiv/papers/1003/1003.3185.pdf), goes into great detail about experimental conditions that result in hot water freezing faster than cold water. An excellent, excellent paper, and supports what I have been saying all along. It supplies a plausible reason for the difference which I was unable to provide. > [@](#): > > Although this experiment began with identical conditions, with the exception of the initial water temperature, **the hot water caused the conditions to change.** The melting of the freezer frost produced a change in the thermal conductivity. (my emphasis) > [@](#): > > …we show results from simultaneously placing two hot and cold water specimens in a cooling environment…Once all four specimens reach the same temperature, they cool to 0º C at the same rate. The time to cool to 0º C is the same for hot and cold water \*when all other conditions are the same. \ ***Heating water does not cause it to cool faster than cold water; once the specimen reaches thermal equilibrium, the cooling rates are identical down to 0º C.** > [@The\_Librarian](#): > > …there is no Mpemba effect. Exactly. ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [November 3, 2013, 4:24pm UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/76 "2013-11-03T16:24:43Z")
> [@Musicat](#): > > An excellent, excellent paper, and supports what I have been saying all along. It supplies a plausible reason for the difference which I was unable to provide. (my emphasis) > Exactly. But that’s not the conclusion that the paper comes to – that’s just one particular set of circumstances it investigated. How are you and **The Librarian** reading that paper and still saying “There is no Mpemba effect”? The paper’s conclusion says (bolding mine): > [@](#): > > The Mpemba effect, describing the phenomenon of initially hot water freezing before cooler water, occurs only when the water supercools and the cooler water has a lower nucleation temperature than the warmer water. The Mpemba effect is not observed if the hot water freezes first but all conditions during cooling are not “identical,” this is the result of increased thermal conductivity. In this case, the hot water container affected the experimental conditions. > > Under normal conditions, ice that is warmed from less than 0 °C will always begin melting when its temperature reaches 0 °C. However, when liquid water is cooled from above 0 °C, it often will not begin freezing until it has supercooled to several degrees below 0 °C. **This is why hot water can freeze before cooler water when all experimental conditions are identical except for the initial temperatures of the water.** ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [November 3, 2013, 5:23pm UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/77 "2013-11-03T17:23:43Z")
That paper also shows that you could get different results depending on how you define “freezing.” The rest of the conclusion points out that, assuming the hot water does NOT change the environment (by, for instance, melting through coils or the like), it always reaches 0 °C after the colder water does – so if you define freezing as “water hits 0 °C,” you may not see any Mpemba effect. But if you define it as the point where the latent heat of fusion is released, as that paper does, you can get 100 °C water to freeze before 0 °C does, based largely on the different temperatures the water actually freezes at. To my mind, Figure 19 is fairly important here – it shows that heating a sealed sample of water, whether it is tap water or distilled water, can cause its spontaneous freezing temperature to change. The paper text says: “We believe that [the major changes in spontaneous freezing temperature] are the result of the destruction and/or production of nucleation sites (motes) in the water, as proposed by Dorsey.[sup]6[/sup]” Now I’m reading Dorsey’s paper, “The Freezing of Supercooled Water” from 1948. It should be noted that this paper, and several other places on the Internet, cites this paper as: N. E. Dorsey, “The freezing of supercooled water,” Transplant. Proc. 38, 246–328 (1948). But it’s not actually in **Transplantation Proceedings** , which as far as I can tell doesn’t go back to the 1940’s anyway; it seems to have started in the late 1990’s. Dorsey’s paper was actually published in **Transactions of the American Philosophical Society** , and is available on JSTOR at least. ---
**Author:** ![The\_Librarian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/the_librarian/32/402_2.png) [@The\_Librarian](https://boards.straightdope.com/u/The_Librarian)\ **Post date:** [November 5, 2013, 9:19pm UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/78 "2013-11-05T21:19:21Z")
> [@chorpler](#): > > But that’s not the conclusion that the paper comes to – that’s just one particular set of circumstances it investigated. How are you and **The Librarian** reading that paper and still saying “There is no Mpemba effect”? The paper’s conclusion says (bolding mine): Supercooled water exists. Supercooled water != Mpemba. There is no Mpemba effect where you can reliably freeze your icecream faster when it’s hot. All claims referring to the icecream have no factual basis. Mr. Mpemba witnissed a container of water getting supercooled and taking forever to freeze. Dr. Denis G. Osborne was lazy or easily impressed. A little research could have found N. E. Dorsey or other works on supercooling. There is no Mpemba effect ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [November 6, 2013, 2:44am UTC](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662/79 "2013-11-06T02:44:27Z")
Perhaps there’s a disconnect in what we’re talking about here, but clearly under some circumstances hot water will freeze faster than cold water, so yes there is an Mpemba effect, since it seems like that should be impossible. As you point out, however, it’s certainly not absolute, or even reliable, except perhaps in specific circumstances like a particular freezer. [Previous page](https://boards.straightdope.com/t/hot-water-makes-ice-cubes-freeze-quicker/356662.md?page=3)