Naked Science Forum

General Science => General Science => Topic started by: texican on 11/07/2008 10:06:55

Title: Can frost-free freezers account for the hot water freezing first claim?
Post by: texican on 11/07/2008 10:06:55

Les Moore  asked the Naked Scientists:

On a recent show (http://www.thenakedscientists.com/HTML/podcasts/) you discussed why hot water might freeze quicker than cold water.

Decades ago the answer was much more simple.  No one had 'frost free' freezers so the inside of the freezer was always covered by a layer of  frost that acted as an insulator.  When an ice cube tray was filled with hot water it melted through the insulating layer of frost and contacted the freezer directly allowing the ice to freeze faster than  if a tray of cold water was used.

Les Moore
Austin Texas

What do you think?

Title: Can frost-free freezers account for the hot water freezing first claim?
Post by: lyner on 13/07/2008 13:20:35

It's an idea but I feel that water at 20C would be just as likely to melt the film of ice.
I had an idea that a warm bowl of water would raise the fridge temperature enough to activate the thermostat  and turn the compressor on earlier than it would normally come on - lowering the internal temperature and speeding up the freezing of the sample.
I think it's just a bit of 'fancy' really tho'.

Title: Can frost-free freezers account for the hot water freezing first claim?
Post by: JonBoy on 14/07/2008 09:09:55

if what all of you are saying is true then cold water would freeze first in frostfree freezers

Title: Can frost-free freezers account for the hot water freezing first claim?
Post by: JonBoy on 14/07/2008 09:11:07

Quote from: sophiecentaur on 13/07/2008 13:20:35

I think it's just a bit of 'fancy' really tho'.

it does sound very fancy
LOL!!

Title: Can frost-free freezers account for the hot water freezing first claim?
Post by: lyner on 14/07/2008 11:43:37

Quote from: JonBoy on 14/07/2008 09:09:55

if what all of you are saying is true then cold water would freeze first in frostfree freezers

Yes. I think it's an old wives' tale because it flies in the face of thermodynamics . If it has been seen to happen, there must be something else to account for it. Inside a frost free freezer - as long as the fan is blowing all the time- is a pretty ideal situation so you you would expect 'real Science' to apply.