Why does boiling/hot water freeze faster than cool water?

Answer 1

Hot water freezes faster than cold water. Most experts say that, all things being equal, cold water freezes faster. However, things are not always equal. A curious phenomenon known as the Mpemba effect can, under some very specific (and poorly understood) circumstances, result in hot water freezing faster than cold water. One of the several possible explanations for this effect involves evaporation: if you start with extremely hot water, a good bit of it will evaporate (and a smaller quantity of water will freeze faster than a larger quantity).

Notwithstanding the previous explanation, water at room temperature that was once boiled, according to some experts, should freeze faster because the dissolved oxygen has been removed.

Answer 2

It doesn't.

Heating and cooling are (mathematically) exponential in nature. A hot object loses heat at a faster rate than one that is just above room temperature, but that stops when that object reaches the temperature of the other object.

It's like this.

Take a hot object.....say 100° C...and another one at say 30° C. You put these in the freezer. The hotter object will cool...and at some point it will be at 30° C just like the other one, but that one is now much colder than 30° C....it's probably near 0° (or whatever -- it's immaterial).

Anyway, the point is, once the 'hotter' object reaches 30° C it will then have to go thru the same cooling process as the other one. Clearly it won't do so any faster than the other one. Not unless you are aware of some laws of physics that I am not.

Obviously the colder object will reach freezing faster than the hotter one. I wish I had a way to show you diagrams, it would help make this easier to 'see'.

Answer 3

The "scientific"answer is that the molecules of water are in a more excited state when the water is warm thus more able to exchange heat, this loosing heat faster and freezing faster. Well, that is the scientific answer, but I have had a lot of schooling and my point is "doesn't the hot water have to reach the state of the cold water prior to freezing, thus negating the above argument?

Answer 4

Is your home freezer it won't, however in certain controlled conditions (very cold/very dry) hot water will chill faster because of convection. When the water vapor rises very quickly it super-cools the surface of the water.

The same thing can also cause evaporating water to leave frost in a clay dish left out on a hot southwestern summer day.

Answer 5

Yes, pastas could be pre-blanched, drain them dry and do not run or soak in cold water, make sure it doesn't come into contact with water after draining then it should just keep well for at least 2-3 days, trick is to cook them till al dente stage and toss on cool marble slabs with olive oil..and wallow you get the old good pasta that needed no extra time just to finish off.

Answer 6

it doesn't. cold water freezes faster and warm water boils faster.

Answer 7

It doesn't, and you can easily test this by putting two dishes of water in your freezer... check it out. The whole point of science is that one experiment is worth 10,000 references or authorities....

Answer 8

This seems to get asked every few days .... here's your answer and yes it can happen under the right conditions -

http://www.math.ucr.edu/home/baez/physics/General/hot_water.html