Does hot water really freeze faster than cold water?

Question

I've heard that hot water expands and the molecules are not as dense. Therefore, It freezes faster than cold water, but it seems to me that it still has to reach 32 degrees F in order to freeze and it would take longer for hot water to reach that tempature. Thanks

Answer 1

Bingo. Water no matter what it's starting temp. will freeze at 32 degrees F, unless there is a solute in there, like salt. First the water needs to cool down before it freezes. Now, the volume of the previously hot water that froze versus the cold water that froze would be less because hot water takes up more volume than cold water. So, in essence, if you had ' equal ' amounts of hot and cold water, there is actually less hot water than cold water because the hot water molecules take up more room

Answer 2

You are correct, water freezes at 32F, so the longer it takes to get down to that temp., the longer it takes to freeze, hence hot water will take longer to freeze than cold water, not shorter. Hot water freezing faster than cold water is an old wives' tale that makes no sense by any understanding of science.

Answer 3

oh come on

think about it

it will take some finite time for hot water to be cooled down to the temperature we are calling cold - from that point on both will take the same amount of time therefore hot water will take longer to freeze than cold

or are you saying that this glass of water will freeze faster than that glass of water at the same temperature because at some time in the past it was hotter ??

Answer 4

Most of the time the impurities in hot water has either settled or boiled off. Making the water faster to freeze.

Answer 5

"does hot water freeze faster than cold
water?


- Freezing requires the removal of heat from the water.
- Hot water contains more heat than cold water. (Duh!)
- Heat is extracted from the water at a rate which depends on the
surface area exposed to the freezer, and the container insulation
efficiency.


I suppose that you could argue that hot water contained in sterling
silver (high heat conductivity) pot might freeze faster than cold
water sitting in a covered styrofoam cup, but it has nothing to do
with the *water*....only with the rate at which heat can be removed
through the different containers.


In similar containers and for similar quantities, cold water freezes
faster than hot water.

(HOPE YOU AGREE....)

Answer 6

It was thought that this was true, so it was experimented with many many times. However, there never seemed to be a clear case where the hot water froze faster. It is just one of those things that we'll never know.

Answer 7

yes, the particles are moving around allowing mor cold air to get in between causing it to freeze faster than cold water

Answer 8

yes because hot water evaporates so there is less hot water than cold one so it freeze faster

Answer 9

My guess is that it's one of those thermodynamics brain teasers. It's like saying that a frozen pond has more heat than a glass of boiling water. Technically, that's correct, but the practical implications are quite different.

Answer 10

hmmmm....good question...

You would assume that even if initial cooling was more rapid, as coming down it would have to pass the temperature of water put in cool. Therefore cool water would have a head start?