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Fact or fiction ?

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Fact or fiction ?

Water that has been previously boiled freezes faster than water that has not been boiled.  Fact or fiction ? 
13 REPLIES
TORPC
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Re: Fact or fiction ?

60/40 Fact
Although that is my gut instinct
That said I feel an experiment should be done to make a conclusive answer
Ok after seeing
[quote=http://math.ucr.edu/home/baez/physics/General/hot_water.html]
History of the Mpemba Effect
The fact that hot water freezes faster than cold has been known for many centuries.  The earliest reference to this phenomenon dates back to Aristotle in 300 B.C.  The phenomenon was later discussed in the medieval era, as European physicists struggled to come up with a theory of heat.  But by the 20th century the phenomenon was only known as common folklore, until it was reintroduced to the scientific community in 1969 by Mpemba, a Tanzanian high school pupil.  Since then, numerous experiments have confirmed the existence of the "Mpemba effect", but have not settled on any single explanation.
"The fact that water has previously been warmed contributes to its freezing quickly; for so it cools sooner.  Hence many people, when they want to cool hot water quickly, begin by putting it in the sun. . ."

I am now 70/30 Grin


Edit:
Fixed quote
Community Veteran
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Re: Fact or fiction ?

I would have guessed that it should be the other way around.
Boiling will remove a lot of impurities and doesn't ice crystals tend to form around certain impurities?
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Re: Fact or fiction ?

nanotm
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Re: Fact or fiction ?

something to do with the molecules being in a more ready state to give off energy when excited (warm) to when there in a more dormant state .....
its something we learned about in secondary school some 20 odd years ago,
interstingly enough its also why on a really cold night if you drive your car with the heating on it will have more frost on the windscreen than if you don't .......

its all about energy transfer
just because your paranoid doesn't mean they aren't out to get you
VileReynard
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Re: Fact or fiction ?

This is obviously wrong.
Take two equal containers of water, one hot and one cold.
Just suppose the hot one cools more rapidly.
At some point, both containers will be at the same temperature.
And so the absolute best they can do is to take the same amount of time to freeze.

Community Veteran
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Re: Fact or fiction ?

If this is true I can't see a time difference that is measurable outside a laboratory.
And no way am I going to put hot water in my freezer and expect it to use less energy to freeze it.
Maybe I can believe in a fractional freezing speed difference but it must cost more energy.
TORPC
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Re: Fact or fiction ?

You do not put boiling water in the freezer
Quote from: gleneagles
Water that has been previously boiled freezes faster than water that has not been boiled.  Fact or fiction ? 
VileReynard
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Re: Fact or fiction ?

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Re: Fact or fiction ?

Quote from: TORPC
You do not put boiling water in the freezer

Quote
but the gist of it was that if you had two wooden buckets of a given size, one containing hot water and the other containing cold water (with precise temperatures specified in each case), and if you exposed said buckets to an air temperature of such-and-such, which one would freeze first?

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

Quote
They argue that the rate at which energy is released varies with the initial state of the water and so calculate that hot water is able to release energy faster when it is placed into a freezer.
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Re: Fact or fiction ?

Quote from: billnotben

Boiling will remove a lot of impurities and doesn't ice crystals tend to form around certain impurities?


Boiling would not remove impurities, it would actually concentrate any impurities by reducing ( through evaporation) the amount of water. Which is one of the reasons that warm water may freeze quicker. A container of warm water in a freezing environment would evaporate quicker, with a greater temperature difference...therefore less to freeze.
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Re: Fact or fiction ?

Percentage-wise how much faster does hot water freeze?
Does it depend on the volume or mass?
Does it depend on the start temperatures or final temperature?

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nanotm
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Re: Fact or fiction ?

its about the change of molecular structure caused by the act of boiling the water,
if you take two sealed pressure vessels with the same volume of cold water, raise one of them to boiling point and then allow it to cool down to room temperature and then place both vessels in a freezer the one that was boiled will freeze faster, because of the change to the molecular bonds caused by the boiling
its all about molecular state change.....
just because your paranoid doesn't mean they aren't out to get you
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Re: Fact or fiction ?

Quote from: doris
Boiling would not remove impurities

I was thinking particularly of hard water areas and the calcium carbonate content.