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Author Topic: Will hot water freeze faster than cold water?  (Read 37522 times)

Offline lightarrow

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Will hot water freeze faster than cold water?
« Reply #75 on: 09/09/2010 13:32:37 »
I am under the school of thought that "hot water" cannot freeze as long as it stays "hot water". :P
This is a good point  ;D
 

Offline Joe L. Ogan

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Will hot water freeze faster than cold water?
« Reply #76 on: 09/09/2010 14:11:01 »
Is this a coincidence?


Well, you do know that if you get enough monkeys typing, one of them will eventually produce Hamlet  ;D
How can you make such a statement?  Have you ever performed the experiment?  Have you ever seen a monkey type?  Is this a scientific statement?  Is this generally accepted by the scientific world?  Thanks for comments.  Joe L. Ogan
 

Offline lightarrow

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Will hot water freeze faster than cold water?
« Reply #77 on: 09/09/2010 17:49:06 »
So, how did we get on the spaceship.  Is this relative to the topic? Did you read the URL quoted above?  Thanks for comments.  Joe L. Ogan
Yes, I've read it, but none seems to have answered my question about blondes and brunettes:

"brunettes get from their husbands more money than blondes!"

Amazing effect! I will name it: "lightarrow effect".

(Possible explanation: *those* brunettes have richer husbands because, not being as "flashy" as blondes in that county, they had to learn how to be smarter and so they succedeed to marry the richer men there :)).
« Last Edit: 09/09/2010 17:55:05 by lightarrow »
 

Offline Geezer

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Will hot water freeze faster than cold water?
« Reply #78 on: 09/09/2010 18:46:20 »
Is this a coincidence?


Well, you do know that if you get enough monkeys typing, one of them will eventually produce Hamlet  ;D
How can you make such a statement?  Have you ever performed the experiment?  Have you ever seen a monkey type?  Is this a scientific statement?  Is this generally accepted by the scientific world?  Thanks for comments.  Joe L. Ogan

I believe it's well accepted. It's simply a case of having enough monkeys, typewriters and time.
 

Offline Joe L. Ogan

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Will hot water freeze faster than cold water?
« Reply #79 on: 09/09/2010 18:51:13 »
tehehe Thanks for comments.  Joe L. Ogan
« Last Edit: 10/09/2010 17:53:21 by Joe L. Ogan »
 

Offline heathhutt

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Will hot water freeze faster than cold water?
« Reply #80 on: 13/09/2010 11:59:33 »
yes hot water freeze faster than cold water because there are several things that help the hot pail freeze faster than the cold pail. Here are what is thought to be the most significant factors:
The hot water is more likely to be supercooled. This means that the hot water's temperature is more likely to cool to temperatures below zero degrees Celsius. In the cold non-supercooled water, ice crystals form and float to the top, forming a sheet of ice over the top of the water, creating an insulating layer between the cooler air and the water. This ice sheet also stops evaporation. In the hot water that has become supercooled (thus, no longer hot) the water, when it does freeze, freezes throughout, creating more or less of a slush before freezing solid.

Why is hot water more likely to be supercooled? Because hot water is less likely to contain tiny gas bubbles. Gas bubbles form from dissolved gasses as the water cools. When the hot water was heated, these dissolved gasses may have been driven out. In cold water, ice crystals use the tiny bubbles as starting points for formation (in physics, we call them nucleation points). But in the hot water, there are no bubbles, so there aren't as many starting points for the ice crystals.

Dissolved gasses also lower the freezing point. Since heated gas is less likely to contain dissolved gasses, it's more likely to freeze first.
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« Last Edit: 05/01/2011 09:49:57 by peppercorn »
 

Offline lightarrow

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Will hot water freeze faster than cold water?
« Reply #81 on: 13/09/2010 15:57:41 »
yes hot water freeze faster than cold water because there are several things that help the hot pail freeze faster than the cold pail. Here are what is thought to be the most significant factors:
The hot water is more likely to be supercooled. This means that the hot water's temperature is more likely to cool to temperatures below zero degrees Celsius. In the cold non-supercooled water, ice crystals form and float to the top, forming a sheet of ice over the top of the water, creating an insulating layer between the cooler air and the water. This ice sheet also stops evaporation. In the hot water that has become supercooled (thus, no longer hot) the water, when it does freeze, freezes throughout, creating more or less of a slush before freezing solid.

Why is hot water more likely to be supercooled? Because hot water is less likely to contain tiny gas bubbles. Gas bubbles form from dissolved gasses as the water cools. When the hot water was heated, these dissolved gasses may have been driven out. In cold water, ice crystals use the tiny bubbles as starting points for formation (in physics, we call them nucleation points). But in the hot water, there are no bubbles, so there aren't as many starting points for the ice crystals.

Dissolved gasses also lower the freezing point. Since heated gas is less likely to contain dissolved gasses, it's more likely to freeze first.
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Ok, I give you two pails, one with hot water and the other with cold water. You put them both in the fridge and the initially hot water freezes slower than the other (as it should do): the cold water I gave you were previously boiled to remove any gas dissolved in it.

Where is the effect now?
« Last Edit: 05/01/2011 09:50:26 by peppercorn »
 

Offline lightarrow

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Will hot water freeze faster than cold water?
« Reply #82 on: 13/09/2010 16:03:48 »
Quote
The hot water is more likely to be supercooled. This means that the hot water's temperature is more likely to cool to temperatures below zero degrees Celsius. In the cold non-supercooled water, ice crystals form and float to the top, forming a sheet of ice over the top of the water, creating an insulating layer between the cooler air and the water. This ice sheet also stops evaporation. In the hot water that has become supercooled (thus, no longer hot) the water, when it does freeze, freezes throughout, creating more or less of a slush before freezing solid.
And when you put the initially hot water in the fridge it doesn't become cold? And when it becomes cold it can't have the same effects of the initially cold water?
 

Offline grizelda

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Will hot water freeze faster than cold water?
« Reply #83 on: 05/01/2011 02:46:00 »
As it was explained to me in grade six, the amount of energy required to freeze the water is much greater than the amount needed to reduce its temperature to the freezing point. Some of the hot water will evaporate in the process, so less energy is needed to freeze the smaller amount of formerly hot water, so it will freeze faster.
 

Offline lightarrow

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Will hot water freeze faster than cold water?
« Reply #84 on: 05/01/2011 14:59:24 »
As it was explained to me in grade six, the amount of energy required to freeze the water is much greater than the amount needed to reduce its temperature to the freezing point. Some of the hot water will evaporate in the process, so less energy is needed to freeze the smaller amount of formerly hot water, so it will freeze faster.
...so it's not true that "hot water freezes faster" because it's "less" water, it's naive just to make any comparison...
 

Offline grizelda

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Will hot water freeze faster than cold water?
« Reply #85 on: 05/01/2011 21:54:20 »
True. You start out with the same amount of water, but end up with a different amount of ice. But the hot water will freeze first. The amount that evaporates won't freeze at all.
 

Offline lightarrow

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Will hot water freeze faster than cold water?
« Reply #86 on: 06/01/2011 17:37:14 »
The amount that evaporates won't freeze at all.
Does it magically disappear?  :)
It condenses and freezes on the freezer's walls.
 

Offline grizelda

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Will hot water freeze faster than cold water?
« Reply #87 on: 06/01/2011 21:13:19 »
Actually, it forms frost, which does not go through a condensation process. Anyway, the experiment is over when the containers of water have turned to ice.
 

Offline Geezer

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Will hot water freeze faster than cold water?
« Reply #88 on: 06/01/2011 21:46:27 »
Actually, it forms frost, which does not go through a condensation process.

Yes, but you still have to remove the thermal energy that was in the water vapour.
 

Offline grizelda

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Will hot water freeze faster than cold water?
« Reply #89 on: 07/01/2011 02:14:21 »
The thermal energy was taken from the hot water, causing it to cool faster. If it gives it up to the freezer, it causes both containers to cool more slowly.
 

Offline Geezer

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Will hot water freeze faster than cold water?
« Reply #90 on: 07/01/2011 02:42:04 »
The thermal energy was taken from the hot water, causing it to cool faster. If it gives it up to the freezer, it causes both containers to cool more slowly.

Sorry. I'm not following you there.
 

Offline Joe L. Ogan

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Will hot water freeze faster than cold water?
« Reply #91 on: 07/01/2011 03:37:11 »
The thermal energy was taken from the hot water, causing it to cool faster. If it gives it up to the freezer, it causes both containers to cool more slowly.

Sorry. I'm not following you there.

Hi, Geseer.  Why don't you do the experiment?  Then you can tell the doubters that the boiling water really does freeze faster.  Thanks for comments.  Joe L. Ogan
 

Offline Geezer

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Will hot water freeze faster than cold water?
« Reply #92 on: 07/01/2011 05:15:15 »
The thermal energy was taken from the hot water, causing it to cool faster. If it gives it up to the freezer, it causes both containers to cool more slowly.

Sorry. I'm not following you there.

Hi, Geseer.  Why don't you do the experiment?  Then you can tell the doubters that the boiling water really does freeze faster.  Thanks for comments.  Joe L. Ogan

Can't. It warmed up again.
 

Offline grizelda

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Will hot water freeze faster than cold water?
« Reply #93 on: 07/01/2011 09:10:41 »
The formation of the water vapour took heat out of the hot water. If it gives up that heat to the freezer, the cooling of water or formation of ice in the containers will take longer.
 

Offline lightarrow

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Will hot water freeze faster than cold water?
« Reply #94 on: 07/01/2011 14:48:08 »
Anyway, if it's because of some water which vaporizes from the container and so it's less water which actually have to be frozen, or whatever other mechanism, the statement "hot water freezes faster than cold water" is not a scientific statement.
You can give it a meaning in english language, but not in science.
To give it a scientific meaning, you should prove that *everything else being equal*, hot water freezes faster. But this condition is not satisfied if you compare different amounts of water.

So the question now is: is this a scientific thread or a chat thread?
 

Offline grizelda

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Will hot water freeze faster than cold water?
« Reply #95 on: 07/01/2011 21:10:35 »
Well, there are two ways to ask the question.
Which freezes faster, an equal amount of hot water or cold water?
Which will produce a stated amount of ice first, hot water or cold water?
You will get different answers to each of these questions.
 

Offline lightarrow

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Will hot water freeze faster than cold water?
« Reply #96 on: 09/01/2011 20:56:34 »
Ok I ask you a similar question:
There are two people A e B and B has a better job than A, let's say A gets 2,000€ per month and B gets 4,000€ per month. Both starts to work at the same time and with 0€.
Who will be able to buy first a car which costs 20,000€?

Of course it's possible that after 4 months a thief takes away all the B's money...
 

Offline grizelda

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Will hot water freeze faster than cold water?
« Reply #97 on: 09/01/2011 21:46:56 »
Depends on whether B has insurance. The fact that hot water behaves like hot water cannot be held against it: you can only realize that the question is inconsequential and the answer only a curiosity.
 

Takahiro Niki

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Does hot water freeze faster than cold water?
« Reply #98 on: 05/04/2011 17:30:02 »
Takahiro Niki  asked the Naked Scientists:
   
My name is Takahiro Niki and I am in American school of Warsaw myth busters class.

My question is that Does hot water freeze faster than cold water?

If you know answer, can you send me back?

Bye.

What do you think?
« Last Edit: 05/04/2011 17:30:02 by _system »
 

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Does hot water freeze faster than cold water?
« Reply #98 on: 05/04/2011 17:30:02 »

 

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