Jump to content
Holidays
Local
Radar
Pollen

Archived

This topic is now archived and is closed to further replies.

knocker

Win A Nw Mars Bar.

Recommended Posts

Scientists offer £1,000 reward to explain a hot topic that even left Aristotle in the cold

It is a problem whose solution has eluded the finest minds from Ancient Greece and the most dogged students from Tanzania. Potential explanations require esoteric applications of thermodynamics and obscure invocations of supercooling theory. It is also critically important when making ice cream.

Now the Royal Society of Chemistry has offered a £1,000 prize to anyone who can say why hot water freezes faster than cold.

Glory awaits..............

Share this post


Link to post
Share on other sites

Isn't it something to do with the Mpemba effect ?

Evaporation of the warmer water reducing it's mass quicker or something like that - if I'm right I don't like Mars bars so can I have a Crunchie instead please angel.gif

Share this post


Link to post
Share on other sites

Isn't it something to do with the Mpemba effect ?

Evaporation of the warmer water reducing it's mass quicker or something like that - if I'm right I don't like Mars bars so can I have a Crunchie instead please angel.gif

Well that's what it is generally known as but doesn't explain it so , no you can't have a Crunchie.

The problem, in its modern form, began life in 1968 when Professor Denis Osborne, of Dar es Salaam University, visited a Tanzanian school near the shores of Lake Tanganyika.

For five years Erasto Mpemba, a student there, had been working in secret on an experiment involving a kettle, measuring jugs and the school freezer. When the teacher asked if anyone had questions for the distinguished physicist, Mr Mpemba put up his hand.

“If you take two similar containers with equal volumes of water, one at 35C and the other at 100C, and put them into a refrigerator, the one that started at 100C freezes first,†he said. “Why?†Mr Mpemba’s fellow students laughed. His teacher was embarrassed. The professor was sceptical — until he tried it himself. The next year, they published a joint paper on the phenomenon, since known as the “Mpemba effectâ€.

Share this post


Link to post
Share on other sites

Mpemba?

Didn't he play football for South Africa?

​On a more serious note though, does this mean that we should expect a more rapid refreeze in the Arctic if the water is becomming increasingly warmer during the summer months?

Share this post


Link to post
Share on other sites

Isn't it just an urban myth?

Share this post


Link to post
Share on other sites

With the jug of hot water, as the surface cools it becomes more dense than the hot water underneath it. This then creates a circulation whereby the cold dense water drops and the warm water rises, allowing the cold water to be more quickly distributed throughout the jug. Result, the stronger currents/circulation cools the jug of hot water quicker than the jug of warm water!

Is there a cash alternative?

Share this post


Link to post
Share on other sites

I don't think that will wash BFTV. Regarding cash alternatives, any queries please address to JH.

In the 4th century BC, Aristotle wrote a treatise on natural phenomena, called Meteorology. Amid descriptions of earthquakes and hail, there is this observation on ice fishing communities: “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.â€

Later, the French mathematician Descartes noted: “One can see by experience that water that has been kept on a fire for a long time freezes faster than other, the reason being that those of its particles that are least able to stop bending evaporate while the water is being heated.â€

Descartes might have been confident in his explanation of the phenomenon, but today’s chemists are less so. Since 1968, numerous papers have looked at everything from evaporation rates to convection currents, but none has provided a definitive answer.

Share this post


Link to post
Share on other sites

Hot water molecules are smaller then in cold water? i would call this 'frizzle' this is because it freezes so much faster that it's like frying, so how can this be possible you may ask Mr scientist? i don't have a clue! just crossed my mind, so is my theory the one?

Share this post


Link to post
Share on other sites

No good asking me. It's puzzled far superior minds than mine.smile.png

Share this post


Link to post
Share on other sites

  • Recently Browsing   0 members

    No registered users viewing this page.

×