It’s True: Hot Water Really Can Freeze Faster Than Cold Water
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By Laura Sanders, Science News
- March 24, 2010 |
- 12:47 pm |
- Categories: Physics
Hot water really can freeze faster than cold water, a new study finds. Sometimes. Under extremely specific conditions. With carefully chosen samples of water.
New experiments provide support for a special case of the counterintuitive Mpemba effect, which holds that water at a higher temperature turns to ice faster than cooler water.
The Mpemba effect is named for a Tanzanian schoolboy, Erasto B. Mpemba, who noticed while making ice cream with his classmates that warm milk froze sooner than chilled milk. Mpemba and physicist Denis Osborne published a report of the phenomenon in Physics Education in 1969. Mpemba joined a distinguished group of people who had also noticed the effect: Aristotle, Francis Bacon and René Descartes had all made the same claim.
On the surface, the notion seems to defy reason. A container of hot water should take longer to turn into ice than a container of cold water, because the cold water has a head start in the race to zero degrees Celsius.
But under scientific scrutiny, the issue becomes murky. The new study doesn’t explain the phenomenon, but it does identify special conditions under which the Mpemba effect can be seen, if it truly exists.
“All in all, the work is a nice beginning, but not systematic enough to do more than confirm it can happen,” comments water expert David Auerbach, whose own experiments also suggest that the effect does occur.
Papers published over the last decade, including several by Auerbach, who performed his research while at the Max Planck Institute for Flow Research in Göttingen, Germany, have documented instances of hot water freezing faster than cold, but not reproducibly, says study author James Brownridge of State University of New York at Binghamton. “No one has been able to get reproducible results on command.”
That’s what Brownridge has done. One of his experiments, presented online, repeatedly froze a sample of hot water faster than a similar sample of cool water.
Note the word similar. In order for the experiment to work, the cool water had to be distilled, and the hot water had to come from the tap.
In the experiment, about two teaspoons of each sample were held in a copper device that completely surrounded the water, preventing evaporation and setting reasonably even temperatures. Freezing was official when sensors picked up an electrical signal created by ice formation.
Brownridge heated the tap water to about 100° C, while the distilled water was cooled to 25° C or lower. When both samples were put into the freezer, the hot water froze before the cold water. Brownridge then thawed the samples and repeated the experiment 27 times. Each time, the hot tap water froze first.
The experiment worked because the two types of water have different freezing points, Brownridge says. Differences in the shape, location and composition of impurities can all cause water’s freezing temperature — which in many cases is below zero degrees C — to vary widely. With a higher freezing point, the tap water had an edge that outweighed the distilled water’s lower temperature.
Because the experiment didn’t compare two identical samples of water, the mystery of the Mpemba effect is not really solved. “I’m not arrogant enough to say I’ve solved this,” Brownridge says. But he has set some guidelines about when the effect can be seen.
Physical chemist Christoph Salzmann of the University of Durham in England says he’s not convinced the Mpemba effect really exists, because there are innumerable things that influence the timing of freezing, making it impossible to completely control.
Predicting how long it will take for a water sample to crystallize “is a bit like trying to predict when the next earthquake or crash of the stock market will happen,” he says. “I would not want to say that the Mpemba effect does not exist. But I have still not been convinced of its existence.”
Image: Kenn Wilson/flickr
This article made me think of Ice-nine
in other news:
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Peeling a larger apple takes less time than peeling a smaller apple.*
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* when using automated peeler for the large apple and manual for the smaller apple.
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You just can’t call the results of comparing DIFFERENT things science. The fact that different outcomes were observed is utterly predictable.
+1 pixelpusher220
Wasn’t there also JUST an article about this.. something about how perfectly distilled water freezes well below zero?
All he really did was prove that the freezing point of water changes depending on additives, which we already knew (ie: anti-freeze). I don’t see how this in any way confirms or help reproduce the Mpemba effect.
Really wanna blow your mind, take two people with the exact same water samples using the exact same refrigerator.
Find someone who totally believes hot water freezes faster, have them heat water with thermometer and stick in freezer, wait 5 or 10 minutes then check water.
Next, find another person who thinks hot water freezes faster is just stupid. Have them do the same thing (thought without believer around).
If that doesn’t blow your metaphysical concept of reality don’t know what would…
A Ford truck is faster than Ferrari F40.
If the F40 is fueled with diesel.
If the Ford truck is driven by a pro and the Ferrari is driven by your 9 year old.
If the Ford truck is tested on the moon.
I hope everyone in the world reads this article. If I ever have to have another conversation that goes “Did you know hot water freezes faster than cold water?” “No, it doesn’t” “Yes it does, my physics teacher even said so” “No he didn’t, you weren’t listening”, I’m going to lose it.
Yes, but does cold water boil faster than warm water?
Meaningless study. This was already well-known. Alas, comparing two identical samples with the same freezing point, the cooler one will always freeze first.
jakediscreet2, you didn’t finish your description. Right now it sound like my mind should be blown by the fact that you got two people to perform and experiment. Wow.
You left out the part where you describe *what you actually saw*.
killtacular, you probably did hear correctly. You missed the part of the class where he went into details about Atlantian science and his big foot hunting stories.
I once read somewhere that when using a typical ice cube tray, starting with hot water will produce something like 25% less ice in 10% less time than starting with cold water. This was because the hot water experienced greater loss via evaporation and therefore overall required less overall energy loss than the cold water to freeze. However, if you start with 25% less cold water, then you get a similar amount of ice as with a full tray of hot water in even less time.
If only I could remember where I read that. Off to Google, I guess.
Yeah, list of explanation includes evaporation removing some significant amount of the initially equal volumes of water, heating before hand removes gases in the water. It can also depend on your type of freezer, is it a self-defrosting freezer, is there a fan inside that runs some or all of the time even if it isn’t self-defrosting?
If I read this in the Onion, I’d be ROTFLMAO. Thank the gods I don’t actually subscribe to wired.com
It’s true: An obese gorilla weighs less than an anorexic hamster. Scientists in California weighed an emaciated hamster and then compared it to data from the most recent shuttle mission wherein astronauts weighed a severely obese gorilla and found overwhelmingly conclusive evidence that the hamster weighed more than the gorilla. Amazing science!
Isn’t this article supposed to run on April First?
The study isn’t as far off as folks suggest. The question being studied is: Is it possible for hot water to freeze more quickly than cold water? They found a case where this is true, with the stated caveats. Both samples fit a reasonable definition of “what is water?” So it’s not apples vs. oranges, but rather red apples vs. green apples.
How could this save mi life in the most hypothetical situation (without including a jigsaw life trial thing like SAW)???.
@pixelpusher220 and @pilnomi are absolutely right. Please stop telling us about studies that have this much nonsense.
Hope they can find something useful for it…
“It’s True: Wired science writers are retarded”
[Alas, comparing two identical samples with the same freezing point, the cooler one will always freeze first.]
but the world isn’t like this. in the real world … nothing is identical … and the dynamics of things that may look the same … but are not … are worth understanding.
hummm… but if you use different samples of water at the same time, the experiment has no value or meaning whatsoever. The logical thing would be that all samples came from the same bottle or tap or whatever, then test if the hot water freezes quicker than the same water but at room temperature.
I saw this done on an old PBS science show back in the 80s. Newton’s Apple maybe? They took 2 identical ice cube trays, poured hot tap water in one, cold tap water in the other and placed them in the freezer. After a while, they checked and they were both partially frozen, but the contents of the hot water tray had thicker ice than the cold water tray.
Forget about all the jokes. How the hell did this article even get published?
It’s the most retarded thing I have ever read.
Thank you very much for this information. dizi izle |endizi.com |Kurtlar Vadisi Pusu son bölüm izle Wow that is truly amazing dude!
Even though there were different water samples, I still wouldn’t call this experiment complete bunk. What I would have to see is freeze time comparisons and volume comparisons. If the volume of the hot vs cold is same and the freeze time is significantly faster then the cold then I’d say it isn’t complete bunk. If any of those two perimeters don’t hold up then it’s useless.
What’s the freezer like? If it’s one of the old non-frost free models, then you’re probably putting the ice tray on a bed of ice. The tray containing hot water would melt it partially and sink down into the layer. When it refroze there would be a significantly improved path for heat transfer out of the tray, allowing the water to freeze faster than the cold water tray which is surrounded by a layer of insulating air.
I remember being told as a kid in school that hot water freezes faster, but the explanation was different. The logic was that heat expands the water, which in turn creates more molecular surface area for heat displacement. But that didn’t make a lot of sense to me, because the hot water needs to displace much more heat in order to freeze. So I tried it at home, and I wasn’t able to get the hot water to freeze faster. I assumed it was just an old wives’ tale, but I guess there is still some scientific controversy about it.
This is one of those five reason things.
Hot water cools faster than cold water.
While it is cooling it evaporates faster than cold water.
When it gets to the same temperature there is less of it.
Less volume freezes faster.
Sometimes what your mother told you was actually true.
But we know all this, don’t we?
@icecycle: Bingo. You said it better than I ever could. Glad to know there are a few people on the planet using their brains.
@bromikl
Next time I will wait for your explanation.
I think it might be better than my throw away.
(can’t think right now, the clown will get me.)
OK, now I am officially pissed off.
Damn.
I am not an expert and I will not be one here.
Give me another opinion even if it is wrong.
Come on, Cold Fusion?
You have to at least try.
I cannot learn without your input.
(wanna do FTL? feed me.)
I’m not saying I believe in the Mpemba effect, nor am I trying to argue that what is documented in this experiment is earth-shattering news. However, the people who outright say “it can’t happen,” shouldn’t be so hasty to generalize.
Here are a 2 facts for you:
1) Some chemical processes are endothermic
2) Some chemical processes will only occur at specific temperatures
Just because we’re talking “water” doesn’t mean it’s pure water. And if it’s not pure, then there are chemical processes potentially, or rather LIKELY, occurring in it at any given time and temperature. This experiment documents that a non-distilled sample of water can freeze faster. No big surprise there. But the path this might lead down could look something like this:
Is there a certain water solution that, as it is cooling, can trigger an endothermic process that somehow allows the water sample to more rapidly go from temperature A to C than the same solution could go from temperature B to C, where A > B > C?
Or maybe this doesn’t depend so much on the water itself as the environment. Initial observations of this phenomenon were far from controlled. Maybe the observations were made on days where the relative humidity was extremely low.
The same people who are commenting negatively on this article might have been the same people who, hundreds of years ago, would have said, of course the earth is at the center of the universe and the heavenly bodies are fixed to a sphere of glass surrounding it. If curious minds hadn’t taken time to investigate “the obvious,” there are many great discoveries that the world would currently be without.
I never believed that hot water froze faster but I always fill my ice cube trays with warm water. It makes the ice cubes easier to come out when they’re frozen.
Wow, must be nice being a scientist! LOL
Lou
true-anonymity.pro.tc
This article should be titled “less water freezes faster than more water” because we all know thats the case. when you put hot water in a cool environment it evaporates faster than the cool water. Any person who wastes valuable time on a useless experiment like this is no scientist, but a fool instead.
Assuming the experiment in question sought to answer “Does hot water freeze faster than cold water”, it is incredibly bad science. Tap water will freze faster than distilled water, because of nucleation energy.
Have you noticed how the bubbles in sparkling water form in much bigger numbers in contact with the glass? That’s because the energy required for a phase change is smaller near the glass. Instead of forming a round gas bubble (a shpere), at the glass/water interface the bubble has a semi-sphere shape, with a smaller surface area and hence a smaller nucleation (or activation) energy.
Tap water has impurities which act as catalysts for phase changes. Distilled water doesn’t.
Not controlling the impurity variable makes this “experiment” and article garbage. I can deal with iPad toting and take it at face value, but this kind of article really lets me down.
kudos kevjon - I enjoyed your comment. Many years ago a researcher published a paper that noted in water separated into hot and cold samples the hot water would freeze faster in a normal home freezer because the hot water container heated melted a thin layer of in the freezer resulting in better thermal conduction between the the hot water container and the thermal sink of the freezer’s surface. That answered the question for me, and this latest research seems to indicate the effect does not occur if the ‘frost effect’ is not part of the experiment.
Have any of you people actually read the d@mn article?
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The Mpemba effect has been known about for quite a while, and has been sporadically observed. BUT, nobody’s ever been able to reliably demonstrate it. This experiment has taken us a *step* toward that. It’s not proof of anything, except that warm water will freeze before the same sized sample of slightly different cool water.
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It’s a STEP, dammit. Now the next step should be to replace the tap water with distilled water that has had fixed, known amounts of impurities added. If the “warm freezes faster” effect is still *consistently* observed, then the experiment should be repeated using fewer/different impurities. And so on.
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It’s through such a process that we move closer to determining whether the Mpemba effect actually exists. It’s called science.
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And for all of you who’re saying “well duh, warm water evaporates and cools in the process”, read the f’ing article: “two teaspoons of each sample were held in a copper device that completely surrounded the water, preventing evaporation”
Well, it is fairly common when during an extreme cold spells in northern climates for water pipes under houses to freeze on occasion. It is my observation that the hot water pipe is the pipe that always freezes in 3 different homes that I have owned while the cold water pipe running right next to it does not. I have always suspected the reason to be be either caused by a greater temperature differential around the hot water pipe and the surrounding air which creates more active convection so warm air radiated from the hot pipe is replaced quicker with cold air causing it to freeze quicker. Another contributing factor may be when water is heated either in a hot water heater or in a pot a small amount of the mineral content is left behind as it precipitates on the inside of the pot or is left behind in the bottom of the water heater altering the chemistry of the water slightly thereby changing the freezing temperature of the hot water from the cold water. Perhaps it is a combination of both. My suspicion is caused by the first rather then the second reason. I have also noticed when I did not use the hot water during a cold spell that neither pipe froze supporting my first contention.
I’m just waiting for someone to link to rebelscience