Asked by Philip Redfearn ⁽⁹¹⁹⁾
Philip Redfearn 38 days 22 hours ago. (More question by this person)

Is it true that hot water can freeze faster than cold water?

Answer from Ben Morrish ^(7,929)
Ben Morrish 38 days 19 hours ago. More questions answered by this person)
Yes, if the conditions are right (and if you try an experiment in your freezer you might well find conditions are right without you having to try!).

Anyone who has put together a PC will know about one of the factors that can help make this counter-intuitive thing happen - thermal contact!

Answer from Kevin Davey ⁽³⁹⁾
Kevin Davey 38 days 19 hours ago. More questions answered by this person)
If you take 2 identical containers, 1 with hot water and 1 with cold water, and put them in a freezer, the one with cold water will always freeze first. This is basic physics - the extra energy in the hot water will take longer to be drawn out, thus it will take longer to freeze.

Now, if conditions weren't identical with the hot water and the cold water container, there are circumstances where hot water could freeze faster than cold water. But that is not really a valid experiment, since the conditions aren't the same.

Comment from Ben Morrish ^(7,929) 38 days 18 hours ago.
This isn't quite right - the setup you describe could result in the hot water freezing first, if the circumstances in the freezer are right, because the hot water container can change its surroundings in a way that allows it to lose heat faster than the cold water container.

It does depend on a few factors though.

Comment from Kevin Davey ⁽³⁹⁾ 38 days 7 hours ago.
Yes, Ben is right, but it takes quite a few things to line up to have this happen. I realize now I was answering in more practical terms - some people actually think "hot water freezes faster" is the rule, not the exception. It is the other way around.

Answer from Gregory Lewis ^(1,502)
Gregory Lewis 38 days 13 hours ago. More questions answered by this person)
Someone try this, please! In the mean time, I am very suspicious of some of the answers and reasoning to solve this problem, and would have to agree with Kevin Davey: If you have two identical containers, and in one you fill with hot water, the other with cold, then put them in the freezer together, the container with the cold water will freeze first. Why? For the reasons Kevin stated, which is to say basic physics, where the temperature difference is greater between the cup of hot water and the freezer, and therefore would naturally take longer to freeze.

In other words, the rate of temperature drop is the same, so it is a case of which cup of water is closer to the finish line. A hot cup might begin to cool at a faster rate, but that rate slows down as the cup gets close to the temperature of the freezer. Now, eventually the hot water is the same temperature as the water in the cooler cup when it started, but by then, it's too late! The water in the cool cup didn't wait for the water in the hot cup to catch up to it; it continued to cool, also, and is possibly already frozen by the time the water in the hot cup reached the temperature where the cool cup started.

-G

Comment from Ben Morrish ^(7,929) 38 days 13 hours ago.
I've done this, and you can too :)

With the right conditions, the hot container can set itself up with a faster level of cooling which remains faster even when the hot container has reached the temperature of the cold container.

The effect of the hotter water freezing first is known as the Mpemba effect, and it is real. The hotter water won't ALWAYS freeze first, but in the right circumstances it can

Comment from Gregory Lewis ^(1,502) 38 days 9 hours ago.
Hehe, ok Ben, I'm like Archimedes, all theory, and you're like Galileo, proving through empirical research.

-G

Answer from Ronyae ^(4,476)
Ronyae 38 days 12 hours ago. More questions answered by this person)
From what I've heard. note, I stated "heard".

Answer from Sandra E. Graham ^(10,088)
Sandra E. Graham 38 days 10 hours ago. More questions answered by this person)
I remember this question from the game last month. I think my answer was yes, because when water is heated, the little thingies move around so that the freezies can get in between them and freeze faster. Needless to say, I didn't get 'best answer' for this one.

Answer from Dianne Lehmann ^(5,738)
Dianne Lehmann 37 days 13 hours ago. More questions answered by this person)
Hot water is less dense and so even though you fill the ice cube tray as you normally would, there is actually less water in each receptacle. A smaller amount of water will freeze faster than a larger amount. But I do not know how to factor in a higher starting temperature. I am going to say that it only appears to freeze faster.

Answer from Ben Jones ^(7,885)
Ben Jones 19 days 8 hours ago. More questions answered by this person)
There are a number of factors involved which make it hard to say definitively what causes this effect.

One theory is that due to the differences in convection currents (similar to the differences in currents in tropical waters versus cooler locales) the cooler container will tend to freeze from the top down. This effectively means that the top of the water will freeze first and form insulation, reducing direct contact with the air and causing the remainder of the container to freeze more slowly.

Conversely, due to the warmer starting temperature the liquid in the other container will move around faster and is less likely to freeze on top but rather from the bottom and sides first. With no insulation at the top the solution continues to be exposed to direct contact with the chilled air and may cool more rapidly.

Answer from Steven Hebert ⁽⁰⁾ 15 days 20 hours ago. More questions answered by this person)
I agee with the other people but it also depends on how hot the hot water container is.