Why hot water freezes faster than cold water?

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Discussion Overview

The discussion revolves around the Mpemba effect, a phenomenon where hot water is suggested to freeze faster than cold water. Participants explore the conditions under which this effect may occur, share personal experiences, and reference studies related to the topic.

Discussion Character

  • Exploratory
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • Some participants reference a new study claiming to explain the Mpemba effect, suggesting that hot water can freeze faster than cold water under certain conditions.
  • Others caution that the phenomenon does not occur universally and may depend on specific experimental setups, noting that it "almost always does not" happen.
  • One participant mentions conducting a semi-scientific test where they did not observe the Mpemba effect, implying that typical conditions do not support the claim.
  • There is a discussion about conducting personal experiments to test the effect, with expectations that cold water would freeze first based on previous experiences.
  • Humorous exchanges occur regarding the challenges of conducting experiments due to practical issues, such as having too much ice cream in the freezer.

Areas of Agreement / Disagreement

Participants express differing views on the Mpemba effect, with some suggesting it can occur under specific conditions while others assert that it is not a reliable phenomenon. The discussion remains unresolved regarding the general applicability of the effect.

Contextual Notes

Participants note that the occurrence of the Mpemba effect may depend on unusual experimental setups and that typical conditions may not yield the expected results. There are references to personal tests that did not confirm the effect.

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Interesting new study out

It is a phenomenon that has baffled the world’s brightest minds since the time of Aristotle.

Now a team of physicists believe they may have solved the centuries old mystery of why hot water freezes faster than cold water.

Known as the Mpemba effect, water behaves unlike most other liquids by freezing into a solid more rapidly from a heated state than from room temperature.

http://www.telegraph.co.uk/news/sci...hot-water-freezes-faster-than-cold-water.html

Here is the paper
http://www.nature.com/srep/2013/131021/srep03005/full/srep03005.html
 
Physics news on Phys.org
Just to be clear: while the wording of the news article makes it sound like this always occurs, in fact it almost always does not. Special/unusual experimental setups may sometimes enable it to occur.

See the similar discussions links for past discussions including a semi-scientific test I ran once to see if the phenomena would occur (it did not).
 
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russ_watters said:
Just to be clear: while the wording of the news article makes it sound like this always occurs, in fact it almost always does not. Special/unusual experimental setups may sometimes enable it to occur.

See the similar discussions links for past discussions including a semi-scientific test I ran once to see if the phenomena would occur (it did not).

There is too much ice cream in the freezer compartment for me to try it straight away, but I was going to put a cup of boiling water and a cup of water at room temperature in there to see which one froze first. I guess, from what you're saying, the cup at room temperature would freeze first, as one would expect?
 
PeroK said:
There is too much ice cream in the freezer compartment for me to try it straight away, but I was going to put a cup of boiling water and a cup of water at room temperature in there to see which one froze first. I guess, from what you're saying, the cup at room temperature would freeze first, as one would expect?
Yes. In one of the links below (if you can't find it I'll look later), is details of a test where I put 3 or 4 coffee cups with equal amounts of water at various temperatures into a freezer, with a temperature logger probe in each. The profiles were nearly exactly as expected.
 
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Well, if there is too much ice cream in the freezer, you will just have to sacrifice yourself, like a true scientist, and eat all that ice cream to empty the freezer!
 
HallsofIvy said:
Well, if there is too much ice cream in the freezer, you will just have to sacrifice yourself, like a true scientist, and eat all that ice cream to empty the freezer!
We'll help.

Chet
 

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