Cold water doesn't freeze faster/hot water doesn't boil faster

[Rock Hydra]

 

[mugs]

Originally posted by: 91TTZ

Originally posted by: RaynorWolfcastle
For example, hot water is used in Zambonis when resurfacing ice because it freezes faster than warm water. .

They use hot water because it melts the ice more, resulting in a smoother surface.

Right.

 

[mobobuff]

Originally posted by: 91TTZ

Originally posted by: RaynorWolfcastle
For example, hot water is used in Zambonis when resurfacing ice because it freezes faster than warm water. .

They use hot water because it melts the ice more, resulting in a smoother surface.

Thank you.

 

[silverpig]

Originally posted by: mobobuff

Originally posted by: 91TTZ

Originally posted by: RaynorWolfcastle
For example, hot water is used in Zambonis when resurfacing ice because it freezes faster than warm water. .

They use hot water because it melts the ice more, resulting in a smoother surface.

Thank you.

Ever notice the steam coming from one of those? Part of the reason is because the steam carries away a lot of heat as well. It's a well-known refrigeration technique.


Take liquid nitrogen, put it in a chamber and put a really good vacuum pump on it. A lot of the nitrogen will boil off, but the remainder will freeze solid. It's also basically how they may Bose-Einstein condensates.

 

[91TTZ]

Originally posted by: silverpig


Ever notice the steam coming from one of those? Part of the reason is because the steam carries away a lot of heat as well. It's a well-known refrigeration technique.

The steam is there only because hot water was sprayed on the ice. Don't think about it too deeply.

 

[Howard]

Originally posted by: SoulAssassin
Hot tap water has more air in it than room temp tap water, therefore it takes longer to boil.

Why?

 

[CrazyHelloDeli]

I SAY THE PLANE WILL TAKE OFF!!!!

 

[mobobuff]

Originally posted by: Howard

Originally posted by: SoulAssassin
Hot tap water has more air in it than room temp tap water, therefore it takes longer to boil.

Why?

Yeah, I don't know about you, but I see a LOT of air in boiling water.

I remember my chemistry teacher talking about it, he said it delt mostly with molecular movement and convection currents.

 

[smack Down]

Originally posted by: Evadman

Originally posted by: Imp
Isn't it all about how many joules of energy you need to raise the temperature? Like you need to get it to 10J before boiling, but if it's already at 4, you only need to add 6, etc. For the love of God, don't quote me on those values.

1 joule will raise the temp of one mm^3 of water 1 degree. so for your example, if you had 1 mm^3 of water at 94C you would need 6 more joules to boil it in a perfect world. however, the world is not perfect

Umm no, and no. First of all a calorie will raise the temp of 1 cubic cm by 1 degree. And second hitting water to a 100C is not enough to biol the water. Boiling the water requires an additional energy input of 540 calories per gram of water that is converted to water vapor.

 

[Midlander]

Originally posted by: mobobuff

Originally posted by: Howard

Originally posted by: SoulAssassin
Hot tap water has more air in it than room temp tap water, therefore it takes longer to boil.

Why?

Yeah, I don't know about you, but I see a LOT of air in boiling water.

I remember my chemistry teacher talking about it, he said it delt mostly with molecular movement and convection currents.

You see a lot of water vapor (gas) in boiling water. It's not air, which is mainly nitrogen and oxygen, not water vapor.

As for the rest of this discussion, it makes no sense to me. But, I haven't done the experiment or read all the articles.... :beer:

 

[Praxis1452]

Originally posted by: 91TTZ

Originally posted by: MichaelD
Somehow got into this coversation last night w/a coworker. I say that if you put hot water into a pot on the stove, it will boil faster than room temp water in the same pot/same flame. Reverse is true for cold water.

This just makes sense to me. Water freezes at 32F/0C. If you start out w/water at 50F, won't it freeze faster ( on the stopwatch ) than water starting at 75F?

You are correct. The others are wrong.

The people who claim otherwise point to studies that claim that, "in some specific circumstances", hot water can freeze faster than cold water. It's the exception, and not the rule.

it's not always some specific circumstances. It's still not exactly known why hot water will freeze faster therefore there is no rule. Contradictory examples prove it wrong. Stop with the black and white. It's grey already

 

[Parasitic]

Heat transfer has two components: a heat transfer coefficient (material dependent), and a temperature gradient as driving force.
If you have a larger temperature gradient then ideally you should observe quicker heat transfer.

 

[RaynorWolfcastle]

Originally posted by: 91TTZ

Originally posted by: RaynorWolfcastle
For example, hot water is used in Zambonis when resurfacing ice because it freezes faster than warm water. .

They use hot water because it melts the ice more, resulting in a smoother surface.

Actually, it's both reasons (smoother ice, and freezes more quickly), but I didn't feel the need to go into the workings of the Zamboni beyond the question at hand.

 

[91TTZ]

Originally posted by: Praxis1452

it's not always some specific circumstances. It's still not exactly known why hot water will freeze faster therefore there is no rule. Contradictory examples prove it wrong. Stop with the black and white. It's grey already

Re-read my post, then try to dispute it. As it is, my point is true- hot water freezing faster is the exception, not the rule.