Scientists offer £1,000 prize for answer to why hot water freeze faster than cold.

This is very interesting article,i havent heard of this before now but apparently boiling water will freeze before water at room temperature in a freezing enviroment.
The problem got its modern name in 1968, when Tanzanian student Erasto Mpemba posed the question to professors visiting his school.

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'.

www.dailymail.co.uk...

reply to post by auraelium


I don't know but Id bet it has something to do with the natural reaction of the minerals/bacteria in the water. Like certain trace minerals/bacteria something that when cooled ignites them into a more frenzy that can make for faster heating because they're awake already from being cold whereas the ones that are held at room temperature are still stable from not being put into any kind of strenuous condition.

Im completely talking bs right now....but who knows I could be on to something

Heat expands thus having more contact with the cold air?

reply to post by auraelium


Easy.

Water vapour would be my guess.

The warmer water molecules begin to evaporate, whilst separate from the body of water they freeze and sink. This happens repeatedly until the water cools by which time the molecules have reached freezing temperature quicker.

This was posted already.

My science teacher in High school said that hot water freezes quicker than cold or room temperature because of the spacing of the molecules.

reply to post by auraelium


My guess is like this. Water expands into it's crystaline form when freezing and also expands when it is boiling.
The spacing of the water molecules would be closer to the same at boiling and freezing than at freezing and room temp.

Or maybe the orientation of the molecules themselves? In water they are lined up front to back. Maybe in boiling water the orientation is thrown off into a more 3D pattern and then as the water loses heat it doesn't have to move as much to form crystals?

I have no clue really.

Someone call Phage, and he can use the money for an ATS apocalyptic party this fall!
Tis interesting no one has solved this since 1968, is there some quantum flux going on or something?

Peace

Oh and just so you know the exact same thread was started 46 minutes ago!!!!!

Let's see, maybe because the molecules in hot water are moving at a faster rate than cold water, thus effected by the drastic change in temperature. CAN I HAVE MY MONEY NOW? NO FIAT CURRENCY! GOLD ONLY

reply to post by TheNamesZeppelin


Hey that was my guess!!! I get the money first!!

I dont know what environment it has to be in but I've tested this several times in a sub-freezing point environment and the boiling water has never frozen before the cold water.

Boiling water in a mug in the freezer stayed liquid hours after the mug of cold tap water.

My boiling wort never freezes before the cool samples.

Originally posted by Threegirls
reply to post by auraelium

 

Easy.

Water vapour would be my guess.

The warmer water molecules begin to evaporate, whilst separate from the body of water they freeze and sink. This happens repeatedly until the water cools by which time the molecules have reached freezing temperature quicker.

This was posted already.

Very good point. Evaporation causes a loss of heat just like getting out of the shower.

reply to post by GARN40ish


haha, fine, you can have it. But don't spend it all in one place meow.

Molecules move faster when hot water then in cold. Temperature is a measure of the average kinetic energy of the atoms. Molecules move faster in hot water because the heat is giving the molecules more energy. Molecules move slower in cold water because heat has/gives energy and when something is cold it has very little heat. So there is very little energy. So there is very little movement.

wiki.answers.com...


With that maybe the cold is able to freeze the heated water molecules faster because the heated molecules possess more energy then the cold. and since they possess more energy they react faster to temp change then the cold less energy possessing molecules.

My 3 cents..

reply to post by TheNamesZeppelin


NICE!

What makes this so baffling is that the 100C water must at some point reach 35C, and by that point the 35C water is less than 35C. The 100C water never seems to "catch up", as in the classical tortoise problem by Zeno.

However, the problem is deeper than it seems. Don't expect to get the prize money just by staring at it. Perhaps it involves solving systems of differential equations.

reply to post by TheNamesZeppelin

Yea but if it is that simple, surely a scientist would have figured it out since 1968, no? I don't know, it seems so simple yet remains unsolved.

reply to post by Infi8nity


Water expands when it gets cold and contracts when it gets hot.
So is your theory not null, or at least backwards?
I'm really asking because I am not sure of what you're saying.

Long time lurker and 1st time poster here. I felt inclined to shed some light on this one. Molecular spacing only has a small bit to do with this phenomenom. This effect is most pronounced in an enclosed space i.e.- freezer. The reason is convection currents. An ice tray with hot water in it will set up a convection current in the freezer thereby cause rapid dissapation of heat away from the water and to the top of the freezer where it then cools and drops down to absorb more heat from the source and carry it away. This current actually accelerates the freezing process marginally. My step-daughter and I demonstrated this in her science fair project last year actually. I'm quite surprised that a prize is being offered for something modern science is already aware of. Anyway, I hope this helps shed some light on the subject. I can supply my mailing address for the thousand bucks if need be... jk.

Bah! (waves scepter)

The answer is obvious. Dissolved solutes cause freezing point depression. Water that has been heated near boiling and then immediately chilled has less dissolved gas. Therefore, boiled water has a slightly higher freezing point than gas-saturated cold water.