Why does hot water freeze faster than cold?

[Serpo]

Scientists offer £1,000 prize for answer to the question: Why does hot water freeze faster than cold?

Ancient problem has eluded scientists and philosophers for centuries
£1,000 reward offered to member of public who can provide 'convincing explanation' of phenonemon

By Daily Mail Reporter (http://www.dailymail.co.uk/home/search.html?s=&authornamef=Daily+Mail+Reporter)
PUBLISHED: 04:40 GMT, 27 June 2012 | UPDATED: 04:40 GMT, 27 June 2012


(http://www.dailymail.co.uk/sciencetech/article-2165277/Scientists-offer-1-000-prize-answer-question-Why-does-hot-water-freeze-faster-cold.html#comments)



It is the baffling question which has perplexed the world's greatest scientific minds and even eluded great thinkers like Aristotle.
But now scientists have become so infuriated about the mystery of why hot water freezes faster than cold, that they have put up a cash reward to find the answer.
The Royal Society of Chemistry has offered £1,000 for a member of the public to come up with a convincing explanation for the phenomenon, which has mystified humankind.

http://i.dailymail.co.uk/i/pix/2012/06/27/article-0-0F4D298800000578-641_468x352.jpg Puzzler: The phenomenon of hot water freezing more quickly than cold has been dubbed the Mpemba Effect

The scientific problem, which has become known as the Mpemba effect, has also defeated Francis Bacon and René Descartes.

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The problem got its modern name in 1968, when Tanzanian student Erasto Mpemba posed the question to professors visiting his school.
http://i.dailymail.co.uk/i/pix/2012/06/27/article-2165277-0156389400001005-762_233x292.jpg The problem is so ancient its answer is said to have even eluded the great Greek philosopher Aristotle

Mr Mpemba, who had been studying the problem for five years, had asked Professor Denis Osborne, of Dar es Salaam University: 'If you take two similar containers with equal volumes of water, one at 35C and the other at 100C, and put them in a refrigerator, the one that started at 100C freezes first. Why?'
The professor was unable to answer and published a paper on the problem the following year, calling it the 'Mpemba Effect'.
Brian Emsley, media relations manager at the Royal Society of Chemistry, wrote in the Guardian that the winner of the £1,000 prize will need to 'make a convincing case and employ some creative thinking'.
Many standard physical effects are said to contribute to the phenomenon, although no single one has been conclusively proved as the cause.
Theories put forward based on evaporation, convection and supercooling have all been put forward, but as yet the question still remains unanswered.
Members of the public have until July 30 to submit their entries.
They will be pitted against worldwide postgraduate scientists, who, sponsored by the Royal Society of Chemistry, will be tackling the same problem.


Read more: http://www.dailymail.co.uk/sciencetech/article-2165277/Scientists-offer-1-000-prize-answer-question-Why-does-hot-water-freeze-faster-cold.html#ixzz1z1kW4xoO

[Gaillo]

My theory: Thermal inertia. Once it starts the accellerated shedding of heat, it's like a runaway train.

[freespirit]

My theory: Thermal inertia. Once it starts the accellerated shedding of heat, it's like a runaway train.


i was thinking that hot water expands allowing for space between the water molecules making it easier to freeze individual molecules as opposed to closer knit clusters of water molecules. thermal transfer does the rest. one drop of water (hot or cold) will freeze faster than a cup full, under uniform conditions...

does that make any sense?? lol

[mamboni]

My theory: Thermal inertia. Once it starts the accellerated shedding of heat, it's like a runaway train.

You're kidding right? Thermal inertia? LOL Heat has no mass. You must be an engineer!

I had always assumed that hot water froze before cold water because the former has a much lower concentration of dissolved gases. Cold water with it's dissolved nitrogen, oxygen and CO2, to name the main gases, behaves as a eutectic solution that exhibits a freezing point depression.

In college, I was the top student in Physical Chemistry - loved it.

[Xizang]

I assume it's because the hot water triggers the thermo sensors in the refrigerator much sooner, triggering the compressor to come on right away, and run solid until it's frozen.

[mamboni]

I assume it's because the hot water triggers the thermo sensors in the refrigerator much sooner, triggering the compressor to come on right away, and run solid until it's frozen.

This wouldn't explain why hot water pipes always freeze first during a cold winter.

[Gaillo]

You're kidding right? Thermal inertia? LOL Heat has no mass. You must be an engineer!

I had always assumed that hot water froze before cold water because the former has a much lower concentration of dissolved gases. Cold water with it's dissolved nitrogen, oxygen and CO2, to name the main gases, behaves as a eutectic solution that exhibits a freezing point depression.

In college, I was the top student in Physical Chemistry - loved it.

I understand what you mean... let me try to be more clear.
Sure, the heat energy ITSELF has no mass, but it does "transfer" to the colder air around the water. My theory is that when you have a larger amount of heat transferring, it sets up a "current" (kind of like electrical current) and it is that process of heat transfer that has the "inertia". Make sense?

Kind of an "intuitive" approach to the problem... quite often the WRONG way to think about scientific theories! ;D

[Dogman]

Neat link on the problem.

http://www.neatorama.com/2008/08/22/5-really-weird-things-about-water/

[willie pete]

my WAG....maybe because of the extreme temps between the two? and the difference in speed of molecular rotation?

[palani]

Latent heat of vaporization adds additional cooling ... vaporization rate is greater for hot water

http://upload.wikimedia.org/wikipedia/commons/thumb/9/9c/Heat_of_Vaporization_%28Benzene%2BAcetone%2BMethan ol%2BWater%29.png/280px-Heat_of_Vaporization_%28Benzene%2BAcetone%2BMethan ol%2BWater%29.png

http://en.wikipedia.org/wiki/Enthalpy_of_vaporization

And the steam engine did more for the science of thermodynamics than thermodynamics ever did for the steam engine.

[Ares]

I can solve that problem, all it requires is a 1 Billion dollar grant from Washington, 20 years and a couple expeditions later I'll be able to give them an answer.

[Cebu_4_2]

I tried this last winter, was way cold and no wind. Cold water froze first.

[vacuum]

Water molecules hydrogen-bond to each other, forming complex structures within the water. The strength of these bonds are just below chemical bonds. Water at 35 C has already formed a lot of complex structures because it isn't being too disturbed. However, water at 100 C has almost no structures within it. As the water turns to ice, the structures within the water must be broken to form an ice crystal lattice. However, the hot water does not have any structure to it, so it easily arranges into an ice crystal lattice.

[k-os]

I probably has something to do with the fact that water is the only substance on earth that exists in three states naturally.

[Heimdhal]

You're all wrong.....



...Its the jews.

[Horn]

Delta of nomenclature

All cooling systems remove heat, they don't add cold..

the cooling system will operate more efficiently/faster if it is hot.

[Son-of-Liberty]

God wanted water to be special.

It freezes faster when it is hot then cold and it gets less dense when it is colder rather then more dense like everything else.

Imagine how sinking ice would F up most temperate lakes.

[TheNocturnalEgyptian]

http://en.wikipedia.org/wiki/Mpemba_effect

http://math.ucr.edu/home/baez/physics/General/hot_water.html

The UCR link has the nuanced answer.

[Neuro]

I tried this last winter, was way cold and no wind. Cold water froze first.
To be honest I had never before heard (or thought) that hot water froze first. I think I will test it out myself today...

[Ares]

To be honest I had never before heard (or thought) that hot water froze first. I think I will test it out myself today...

I used to play with that effect in high school. Take a glass of boiling water in sub freezing temperatures. Go outside and throw it up in the air, it will turn to snow before it hits the ground. I would only do it when it was below zero outside. But it works, kind of cool to watch.

[Awoke]

I was going to say what FreeSpirit said: Hot water has "excited" molecules with more space in between them, possibly letting entire body of water cool faster.

Just the first thing that jumps into mind.

[Hatha Sunahara]

There is a phenomenon called the adiabatic effect. You can grasp this by noting that you have to add or take away a lot more energy out of water, or any substance to effect a change in state. When boiling water, you can get it up to 212F by adding heat. But to get it to boil (turn to a gas) you have to add a lot more heat. Similarly, when you cool water, you can get it down to 32F but then to make it turn to ice (solidify) you have to take out much more heat. Also, when ice melts, it melts slowly because at the melting point it requires more heat to change its state than to just change the temperature. There seems to be a non-continuous function of energy exchange at the points where water changes state. The state change itself requires more energy to be transferred in or out of the water. For water to go from being hot to ice quicker that from being cold to ice may have something to do with this non-continuous energy transfer at state change points.

Hatha

[vacuum]

There is a phenomenon called the adiabatic effect. You can grasp this by noting that you have to add or take away a lot more energy out of water, or any substance to effect a change in state. When boiling water, you can get it up to 212F by adding heat. But to get it to boil (turn to a gas) you have to add a lot more heat. Similarly, when you cool water, you can get it down to 32F but then to make it turn to ice (solidify) you have to take out much more heat. Also, when ice melts, it melts slowly because at the melting point it requires more heat to change its state than to just change the temperature. There seems to be a non-continuous function of energy exchange at the points where water changes state. The state change itself requires more energy to be transferred in or out of the water. For water to go from being hot to ice quicker that from being cold to ice may have something to do with this non-continuous energy transfer at state change points.

Hatha

This is called latent heat (https://en.wikipedia.org/wiki/Latent_heat) and and the phase transitions from solid to liquid and liquid to gas have a specific heat required to occur. This is related to the molecules each changing state between a lattice, liquid, and becoming a vapor.

[mamboni]

This is called latent heat (https://en.wikipedia.org/wiki/Latent_heat) and and the phase transitions from solid to liquid and liquid to gas have a specific heat required to occur. This is related to the molecules each changing state between a lattice, liquid, and becoming a vapor.

This energy of phase transition is reflected in the freezing point depression (see my prior posting). Water as solution (containing dissolved gases) will have a lower freezing point than "pure" or "purer" water. Only pure water will freeze at 0 degrees C. Also, water at 10 degrees does not know whether it was 90 degrees 3 minutes earlier or 20 degrees. To question this is to question basic thermodynamics. So to state that hot water freezes faster than cool or room temperature water is misleading at best. Heat loss is a first order decay. If the freezing points are the same, then the warmer water will take longer to freeze, always. If the hot water freezes before the cool water, then the cooler water must have a lower freezing point and a higher heat of transition.

[General of Darkness]

It's because Chuck Norris likes it that way.

http://files.abovetopsecret.com/files/img/qp4f92aad8.jpg

http://3.bp.blogspot.com/_UsQ5K5aFt3Y/SVuh-jAj16I/AAAAAAAABFk/PJERlGxaoYg/s400/chuck-norris-rock-demotivational-poster.jpg

http://www.funnymotivationalposters.info/wp-content/uploads/2010/08/Chuck-Norris.jpg

http://cdn.memegenerator.net/instances/250x250/21875538.jpg

[Horn]

You guys are talking about steam, not water.

It works over a certain delta and time scale, and the effect is similar to that of inertia, or terminal velocity, without the velocity.

I didn't read that paper that the Egyptian posted, i remember my physics teacher tellin me this in highschool. It had to do with the efficiency of the heat removal system. Freon in the fridge as example, will expand at a higher rate to remove the heat,

or it's whatever is removing the heat from the water that becomes more efficient at doing the job, nothing to do with the water itself.

You can only remove heat, you can't add cold to any system.

[Uncle Salty]

You can't drink ice.

[mick silver]

as long as my coffee is hot then cold water can be cold

[Hatha Sunahara]

There is an old French proverb: "'It's all good and fine in practice, but will it work in theory?'


Hatha

[slowbell]

I was going to say what FreeSpirit said: Hot water has "excited" molecules with more space in between them, possibly letting entire body of water cool faster.

Just the first thing that jumps into mind.

The faster things move, the harder they crash. Maybe the molecules in the hot water is like a car slamming into a wall. The faster the car is going, the more damage. Maybe the hot water slams into the wall in freezing temps. Where as colder water is like an old lady easing into a bathtub.

[TheNocturnalEgyptian]

http://www.youtube.com/watch?v=ZGjwe-BCfms

[TheNocturnalEgyptian]

http://www.youtube.com/watch?v=xOVZV6DxaRs

He throws cold water (35F) and boiling water (212F) at the same time. The ambient temperature is -15F.

The cold lands wet. The boiling water is easily surrounded by the air and freezes in midair.

[Horn]

The cold lands wet. The boiling water is easily surrounded by the air and freezes in midair.

Now that's efficient heat removal.

[Silver Rocket Bitches!]

Heat expands and cold constricts. Seems logical that expanded water molecules would freeze faster than constricted ones.

[mamboni]

Heat expands and cold constricts. Seems logical that expanded water molecules would freeze faster than constricted ones.

I don't know. Using that logic, one would expect that a semi-hard dick would take longer to get fully erect than a limp one. This is a hard problem.

[Horn]

I don't know. Using that logic, one would expect that a semi-hard dick would take longer to get fully erect than a limp one. This is a hard problem.

Lets see, maybe me & mamboni can figure this out if we put our heads together?

The air surrounding (in your example) the hotter water molecules would expand at a higher rate away from the water.

Oh wait, how'd you get banned...?

[Santa]

Does this suggest that a human would freeze faster than a cold blooded reptilian?

[Horn]

Talk about a "tricky" problem.

Oooh if I had a screen shot of the hot air expanding away in that instance... you'd be dry white toast.

I'm waiting for the "lift".

Liquids are not compressible, or expansionary in your case.

[Gaillo]

Talk about a "tricky" problem.

Oooh if I had a screen shot of the hot air expanding away in that instance... you'd be dry white toast.

I'm waiting for the "lift".

Liquids are not compressible, or expansionary in your case.

There does seem to be a lot of misunderstanding surrounding this problem.

[Horn]

There does seem to be a lot of misunderstanding surrounding this problem.

Perhaps we should look in the mirror?

re-watch!


http://www.youtube.com/watch?v=W2ty3b4EBMg

[Gaillo]

Perhaps we should look in the mirror?

re-watch!


Whatever, Guy.

You complain about a certain thread "derail", I correct the situation for your satisfaction, then you proceed to do your own derail? There's just no pleasing some people. The attempt to do so won't be extended again.

[Horn]

I correct the situation for your satisfaction,

Problems are often solved by looking in the mirror. Hot air in this case being the mirror.

No derail here.