Researchers claim to have discovered why warm water freezes faster than cooler water

Nov 04, 2013 by Bob Yirka report
O:H-O bond in water ice. Credit: arXiv:1310.6514 [physics.chem-ph]

(Phys.org) —A team of researchers at Singapore's Nanyang Technological University believes they have solved the mystery of why warm water freezes faster than cooler water. It has to do with the way energy is stored in the hydrogen bonds between water molecules they suggest in their paper which they've uploaded to the preprint server arXiv.

It's long been known that freezes faster than cooler water, (known as the Mpemba effect) going all the way back to Aristotle, but until now, despite a lot of effort by many scientists over thousands of years, no one has been able to offer a reasonable explanation as to why it happens. Now, the team in Singapore appears to have solved the riddle—it's due, they claim, to the small amount of energy stored in stretched bonds.

As everyone knows, have one oxygen atom and two hydrogen atoms—all held together by covalent bonds (the sharing of electrons). What's also known is that with water molecules, hydrogen atoms are also attracted to the oxygen atoms in other nearby water molecules—a force called a hydrogen bond. But, at the same time, the water molecules as a whole are repelled by one another. The team in Singapore has noted that the warmer water gets, the more distance there is between the water molecules due to the repellant force between them. That they say, forces the to become stretched out, and stretching out a bond means that there is energy being stored. That energy, the researchers suggest, is released as the water is cooled allowing the molecules to become closer to one another, and (as every chemistry student knows) giving up energy means cooling.

Warm water has more hydrogen bond stretching going on than cool water, thus it stores more , and has more to release when exposed to freezing temperatures. That is why, the researchers say, it freezes faster than cool water.

At this point, the claims by the research team are still theory—they or others will still need to find a way to prove what they've suggested is true before the scientific community will deem the mystery of warm freezing, solved once and for all.

Explore further: Water found to be an ideal lubricant for nanomachines

More information: O:H-O Bond Anomalous Relaxation Resolving Mpemba Paradox, arXiv:1310.6514 [physics.chem-ph] arxiv.org/abs/1310.6514

Abstract
We demonstrate that the Mpemba paradox arises intrinsically from the release rate of energy initially stored in the covalent H-O part of the O:H-O bond in water albeit experimental conditions. Generally, heating raises the energy of a substance by lengthening and softening all bonds involved. However, the O:H nonbond in water follows actively the general rule of thermal expansion and drives the H-O covalent bond to relax oppositely in length and energy because of the inter-electron-electron pair coupling [J Phys Chem Lett 4, 2565 (2013); ibid 4, 3238 (2013)]. Heating stores energy into the H-O bond by shortening and stiffening it. Cooling the water as the source in a refrigerator as a drain, the H-O bond releases its energy at a rate that depends exponentially on the initially storage of energy, and therefore, Mpemba effect happens. This effect is formulated in terms of the relaxation time tau to represent all possible processes of energy loss. Consistency between predictions and measurements revealed that the tau drops exponentially intrinsically with the initial temperature of the water being cooled.

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Eikka
1.9 / 5 (22) Nov 04, 2013
It's long been known that warm water freezes faster than cooler water


Yet it has never actually been proven to do so. We only "know" it because people keep insisting it does.

This is bunk science at its finest. There is no agreement on exactly what the effect is and under what circumstances it occurs - all we have is anecdotes that someone's managed to do it. There isn't even an agreement on what "freezing" means in this context - whether you see frost on the surface or whether the whole volume goes solid, or whether it simply reaches 0 degrees C.

And as for this idea: the water needs to shed the energy stored in the stretched bonds before it can freeze - to unstretch the bonds to become normal cold water - so even though it loses energy faster, it still needs to get rid of more energy and the rate of energy loss drops the lower the temperature drops, so it can only freeze slower.
beleg
1.3 / 5 (12) Nov 04, 2013
Apparently not all (Fourier) modes of heat dissipation are available in the construct labeled the water molecule.
Eikka
2.4 / 5 (22) Nov 04, 2013
Put simply: water needs to become cold before it can freeze, and in doing so it logically takes on the properties of cold water. The rate of cooling slows down so that one glass of water starting at 100 C can never reach zero faster than one starting at 20 C because it has to get rid of more energy just to get to 20 C and at that point it will be cooling down no faster than the glass that started there!

It's an example of the Zeno's paradox where the hot glass never wins, because first it has to get to where the cold glass was before, where it no longer isn't.

The idea in the article is suggesting instead that water has some sort of "memory" so that it remembers being previously hot even as its temperature is falling.

thus it stores more energy, and has more to release when exposed to freezing temperatures. That is why, the researchers say, it freezes faster than cool water.


That is really a nonsensical statement. It takes more time to release more energy.
VendicarE
2.8 / 5 (16) Nov 04, 2013
I have observed that warm water freezes faster than cold. Even warm water that has no means of evaporative cooling.

The standard explanation is that warm water tends to develop convection that persists as the water cools. Thus formerly warm water has some stronger convection going on compared to cold water even when the formerly warm water is at or below the same temperature as the cold.

The convection increases the rate of heat loss for the formerly warm water compared to the cold, and hence the formerly warm water cools and freezes faster than the cold water.

This explanation makes sense.

The one offered in the article and the research does not.

MR166
2.1 / 5 (19) Nov 04, 2013
Although we like to think that freezing and boiling water always occur at the 0c and 100c, this is not really true. Put some water in a clean glossy smooth cup in a microwave oven and it will go way over 100c before it starts to boil. The same thing happens to water when cooled and not disturbed. The water can become super cooled below 0c and still be a liquid. Put a small ice crystal into this liquid and the entire solution freezes in less than a second. Perhaps water that was once boiled has less dissolved oxygen and gasses in it and freezes at a different rate.
VENDItardE
1.4 / 5 (20) Nov 04, 2013
Scott, just STFU, you are truly stupid.
MR166
1.4 / 5 (16) Nov 04, 2013
I suppose they need to define the temperature of warm and if the water was once boiled or not. Both boiling and ice formation start faster if there are surface irregularities on the container.

A proper test would have to start with water that was once boiled and then brought to room temperature. One half of the sample would then be heated say to 50c and both then refrigerated.
Kedas
2.1 / 5 (16) Nov 04, 2013
Can people stop using 'warm water' like if it's a scientific term!
wealthychef
1.5 / 5 (12) Nov 04, 2013
I have observed that warm water freezes faster than cold. Even warm water that has no means of evaporative cooling.

The standard explanation is that warm water tends to develop convection that persists as the water cools. Thus formerly warm water has some stronger convection going on compared to cold water even when the formerly warm water is at or below the same temperature as the cold.

The convection increases the rate of heat loss for the formerly warm water compared to the cold, and hence the formerly warm water cools and freezes faster than the cold water.

This explanation makes sense.

The one offered in the article and the research does not.



Your explanation does not make sense at least to me. The warm water cools faster than the cool water at first. But eventually it becomes cool water. It then cools at the rate of the cool water, no?
sigfpe
4.5 / 5 (2) Nov 04, 2013
@wealthychef said

> The warm water cools faster than the cool water at first. But eventually it becomes cool water. It then cools at the rate of the cool water, no?

But there is a difference. By time the warm water becomes cool it is in motion due to convection. It's not nonsense to suggest that cool water in motion might cool faster than cool water at rest. I'm not saying this is actually what happens. Just that @VendicarE's claim can't be dismissed out of hand.
MR166
1 / 5 (14) Nov 04, 2013
If I am understanding you Teech you are saying that cold water has to give up more energy to freeze than warm water. Does warm water freeze at a higher temperature than cold water IE it has to give up less energy?
AdamCC
1.5 / 5 (6) Nov 04, 2013
OK folks,

YES, the more rapid freezing of initially warmer water HAS in fact been observed.

TRUE, "warm water" is used loosely here, but various experiments define it quite clearly and demonstrate a range of conditions where this effect can occur.

NO, convection is not by itself a sufficient answer, though it has reputably been put forth as a factor.

NO, you cannot dismiss this effect with the simple statement that "the warm water has to first get to where the cool water started".

And NO, Teech's mumbo-jumbo explanation does not explain this, or make any sense at all for that matter.

The research / thinking in this article is interesting, I hope there is something to it.

Please read up before making assumptions. Here's a pretty good source: http://math.ucr.e...er.html.
AdamCC
2.4 / 5 (5) Nov 04, 2013
How is it possible, the homeopathy works even under the dilutions, which would allow no molecule of the active chemical in the solution?


It isn't. Period. Stop pushing pseudoscience on a science site. You want to talk about that crap, go to a homeopathy website. This site is for the enlightened, who place value in the scientific method and EVIDENCE.
AdamCC
1 / 5 (4) Nov 04, 2013
The plain saying, that something doesn't provide an explanation is not enough. You should prove first, I'm missing/violating some logics there - or it would just mean, you're not smart enough for to understand it.


Spewing a bunch of words does not imply that you are right unless proven wrong. I know you are wrong, because I have researched the current state of the science involved with this principle from multiple reputable sources, and your explanations fit no where in there. They are furthermore fundamentally illogical and violate all sorts of physics principles. I am not going to waste my time with a line by line deconstruction, because honestly anybody with half a brain already knows your ramblings are crap, and if it's not obvious from the first sentence, your crack-pottery positively SCREAMS at the reader when you start going off on something as easily and thoroughly debunked as Homeopathy.
Zephir_fan
Nov 04, 2013
This comment has been removed by a moderator.
antialias_physorg
5 / 5 (3) Nov 04, 2013
Your explanation does not make sense at least to me. The warm water cools faster than the cool water at first. But eventually it becomes cool water. It then cools at the rate of the cool water, no?

There's a number of possible explanations out there. Among them:

a) Warm water evaporates more (more probability for individual molecules to jump from liquid to gaseous phase). So by the time it has cooled to the temperature of a same amount that started of cooler there's slightly less of it in the cup.
Heat exchange is being driven by differential at the SURFACE. A smaller amount of water has a higher surface to volume ratio (i.e. cools faster)

b) The convection current theory goes in a similar direction with the convection current increasing the amount of water that is at the interface to the cool air...like a heat exchanger system where the warmer water will remain in motion for some time through inertia even after cooling to the level of the other cup.

Still no consensus.
RealityCheck
1 / 5 (12) Nov 04, 2013
Hi antialias_p, Zephir, everyone. :) Last paragraph in article:
At this point, the claims by the research team are still theory—they or others will still need to find a way to prove what they've suggested...
My observation of comments is that Zephir's came closest when he alluded to 'volumetric/expansion' involved in freezing water to ice. Unfortunately, Zephir went off on tangents which are virtually insignificant compared to the 'volumetric/expansion' state involved in 'warmed water' which will be more easily re-arranged and 'frozen-in-place' from that already-expanded state rather than having to be 'expanded from scratch' from already-cool denser, not-yet expanded state by 'further' cooling of already cool' (and hence denser) state.

No 'mystery' to me. Not kinematics/thermodynamics or other dynamical aspect that is the over-riding factor, but rather easier to re-arrange an already-expanded state that is closer to the 'expanded state' of the ice crystal forming! Cheers! :-)
SiDawg
1 / 5 (11) Nov 04, 2013
Seems to be a few people disputing the claim in the comments here, and I'm certainly somewhat of a layman on this subject, but for me the most useful description of the effect came from the abstract. Sounds like they're talking about momentum.

In layman terms, it seems what they're saying can be likened to a rubber band: if you start with a loose rubber band sitting on a table, it takes energy to push the sides together. If you start with a stretched rubber band in your fingers, releasing that energy by 'flicking' it off one your fingers, not only returns it to the loose state but it goes further and the sides close together. The further the stretch, the quicker the sides close together. For water, the more energy stored in the bonds, the quicker the release of energy carried through to eventual freeze state.

"the H-O bond releases its energy at a rate that depends exponentially on the initially storage of energy"

Zephir_fan
Nov 04, 2013
This comment has been removed by a moderator.
Donutz
4 / 5 (2) Nov 04, 2013
Have you actually tried it? I have. After the last time I got into this argument, I set up an experiment. It's not hard after all -- just takes a couple of identical glasses, some water, and a thermometer. I ran the experiment 3 times and the warm water DID NOT freeze faster than the cold. The warm water COOLED OFF faster than the cold, because there was more of a thermal gradient, so by the time the two glasses were within a degree or two of freezing you couldn't tell by inspection which one had started warmer. But they both froze at around the same time. Stop arguing and TRY IT YOURSELVES!
SiDawg
1.3 / 5 (14) Nov 04, 2013
The theory that you just proved? You're an idiot. Congrats


Er, ouch? And you're arrogant. How am I an idiot?

Just seemed to me that plenty of people were criticising this research without actually conceptualising it correctly... was providing a conceptualisation. How is what you said useful to anybody?
cantdrive85
1 / 5 (13) Nov 04, 2013
Warm water freezes quicker because water must achieve it's fourth phase to freeze.
http://www.youtub...L6BoH3Ug
Zephir_fan
Nov 05, 2013
This comment has been removed by a moderator.
cantdrive85
1 / 5 (14) Nov 05, 2013
How is what you said useful to anybody?


It's useful to anybody who doesn't want to waste their time reading really stupid comments. Plus since I thought what you wrote was really stupid I thought I should say something to go along with my one karma point. There seems to be a bunch of sissy girly-men here that give one karma points without ever saying anything, I'm not one of those. Now why don't you just sit down and shut up and try to conceptualize the things the smart people are trying to teach you. You might start with Zephir's very good explanation of why warm water freezes faster than cooler water.

Somehow because you make comments that makes you less of a sissy boy troll. No, don't think so. The feigning support of Zeph is apparent, for if it was legit you would have recognized the video I linked was one of Zeph's links, not to mention how often ya misquote him or are flat out wrong in your understanding . You're little more than a Q* sockpuppet troll.
Zephir_fan
Nov 05, 2013
This comment has been removed by a moderator.
SiDawg
1.8 / 5 (15) Nov 05, 2013
Sorry, I didn't realise who "zephir" was. Having now read a few posts about him, your likeminded insistance on writing drivle makes a lot more sense. Such a shame to see a person such as yourself tarnishing a respectable website.

I'm not sure how many people on this website are professional scientists, and how many are just interested laymen. To me, the great thing about this website, is it provides a gateway for laymen like myself to learn about leading edge scientific research without having to subscribe to however many scientific journals. Perhaps scientists working in very specific fields enjoy reading about advances in other fields they wouldn't normally have the time to read. I would imagine true experts in the field pertaining to each article would most likely have read about it already in the source journal, as part of their profession.

There's no room for crackpots and trolls here. Go back to You Tube.
Zephir_fan
Nov 05, 2013
This comment has been removed by a moderator.
Zephir_fan
Nov 05, 2013
This comment has been removed by a moderator.
VendicarE
3.5 / 5 (6) Nov 05, 2013
"But eventually it becomes cool water. It then cools at the rate of the cool water, no? " - Wealthy

No. The difference is that the formerly warm water has convection currents setup during the cooling process that persist as it's temperature drops to and below that of the cool water.

The convection allows the interior water in the container to cool more rapidly while in the cool water, there is little or no convection so the interior water is insulated by the exterior water.

baudrunner
1 / 5 (11) Nov 09, 2013
You're all so amusing. And wrong. Even the article.

Ever try to grow crystals when you were a kid? They take a long time to do so. Spatial separation between water molecules is greater for warm water than it is for cool water. This contributes to the faster rate of cooling (ie energy release) of warm water vs cool water, and this is correct, as described in the article. This provides a momentum for the more rapid crystallization of the warmer water into ice, versus that of the cooler water. Related phenomena are observed in other scientific applications, notably the hysteresis effects of electronic inductive processes.
Mike_Massen
2 / 5 (6) Nov 10, 2013
What seems to be missed here is the experimental method details and in that respect time is of supreme importance !

Just how long was each sample of water at any particular temperature before cooling was proceeded with - this could well point to a form of bonding in undisturbed water which may allow a type of layering which allows water to lose heat more quickly as it transitions to cold versus water that has been cold for a comparatively longer period and perhaps subject to some sort of turbulence or combinatorial paradigm of molecular/bond settling.

What were the lighting conditions too, this can have an interesting effect ?

What method is used to assess water temperature such as without causing disturbance - etc ?

Clearly the experimental method is the key issue.

"Details Matter, as the truth has a habit of hiding in the details"

wealthychef
not rated yet Nov 19, 2013
@wealthychef said

> The warm water cools faster than the cool water at first. But eventually it becomes cool water. It then cools at the rate of the cool water, no?

But there is a difference. By time the warm water becomes cool it is in motion due to convection. It's not nonsense to suggest that cool water in motion might cool faster than cool water at rest. I'm not saying this is actually what happens. Just that @VendicarE's claim can't be dismissed out of hand.


Convection is a very fast changing process compared to cooling, on the order of seconds to form and go away. By contrast, cooling takes minutes or hours. By the time the "warm" water has cooled to the temperature of the "cool" water, I would think the convection in the previously warm water will be the same as in the cool water.
wealthychef
not rated yet Nov 19, 2013
You're all so amusing. And wrong. Even the article.

Ever try to grow crystals when you were a kid? They take a long time to do so. Spatial separation between water molecules is greater for warm water than it is for cool water. This contributes to the faster rate of cooling (ie energy release) of warm water vs cool water, and this is correct, as described in the article. This provides a momentum for the more rapid crystallization of the warmer water into ice, versus that of the cooler water. Related phenomena are observed in other scientific applications, notably the hysteresis effects of electronic inductive processes.


I don't buy it. Momentum is the tendency of a physical object to remain in motion, which is proportional to its mass and velocity. The velocity of a shrinking crystal is miniscule. Momentum cannot be an important effect here compared to the energy of melting/freezing.
baudrunner
1 / 5 (1) Nov 19, 2013
I don't buy it. Momentum is the tendency of a physical object to remain in motion, which is proportional to its mass and velocity. The velocity of a shrinking crystal is miniscule. Momentum cannot be an important effect here compared to the energy of melting/freezing.

Hah! Can you explain that water at the bottom of a lake in winter is almost always at 4 degrees C? That's because water is at its maximum density at that temperature. If you heat or cool that water, it will expand! Please, this is a science site. I expect commentators to be at least a little informed. Back to square one, wealthychef.

And speaking of getting my terminology right, The, uh, velocity (?) of a shrinking crystal?