freezing water...please settle this debate for me!?

Question

my husband swears that hot water freezes faster than cold water. i don't think it makes much difference, but that hot water will freeze more clearly than cold water.

so, what is the optimal temp for water to freeze fast??
hot or cold??

i can't pick a best answer b/c it seems there are many variables in which one temp water will freeze faster than another.

so, i leave it to a vote...first time i ever did this!

thanks, everyone!

Answer 1

Hot water freezes faster. This phenomenon is referred to as the Mpemba effect.

Answer 2

With all parameters equal between two containers of water, except for temperature, it depends on the ratio of the surface area to the volume of the water containers. If the surface area is relatively small, common sense prevails. The hotter water has
more BTU's(heat). It takes some time to get down to the temperature that the cold water started at. Meanwhile the cold
water has also dropped in temperature. This difference continues
as the colder water freezes before the hotter water does.
However, if the surface area is wide compared to the volume,
(such as with a wide soup bowl), then an interesting thing happens. The hotter water evaporates faster and changes one
of those equal parameters - the quantity. Now the quantity of the
originally hotter water is less than the colder water and loses
heat at a faster rate, reaches the temperature of the colder
water before freezing, then proceeds to the freezing point faster
and wins the race.
An ice tray has a relatively wide surface area, so hot water might freeze faster, unless the cold water is near freezing to
begin with, but you end up with less ice due to the initial
evaporation. You could just as well start with less water if what
you want is ice quickly.

Answer 3

Depends on how hot is hot, and what the temperature difference is between the hot and cold:

If you put a tray of water that is cold, say 5°C, in at the same time as a tray of boiling water, at 100°C, then the cold water will freeze first by a long shot.

However, if you have warm water, perhaps 13°C, versus cooler water, say 10°C, in some cases the warm water will actually solidify first, because there isn't as much dissolved gas in the water to interfere with the formation of the ice crystals.

Answer 4

Apparently COLD WATER freezes faster than HOT WATER under some circumstances, and under other conditions hot water freezes faster. What's the explanation?

Hot water that is near the boiling point evaporates a lot faster than cold water. As some of this water evaporates, there is less water left behind to freeze, so it won't take as long. But equally important, evaporation requires energy, which comes from the water. As the hot water is evaporating, it is cooling the water that's left behind.

Both of these factors will increase the rate of cooling of the hot water, and under certain circumstances, make it freeze before the cold water does. The special circumstances require that very little of the heat from either sample of water can escape because of conduction. If the heat can escape quickly by conduction, the cooling effect of evaporation won't be enough to make the hot water freeze first. That's why our first experiment with water in pans saw the cold water freeze first ... heat was able to escape through the pans into the ground beneath, and quickly freeze the cold water, which only had to drop 19 degrees to freeze. When we did the experiment again with styrofoam cups, the heat couldn't escape quickly by conduction, since styrofoam is a good insulator. Instead, the extra cooling provided by evaporation caused the hot water to freeze first.

Answer 5

Generally cold water freezes faster because it is already closer to freezing. I have heard that if you fill an ice cube tray with hot water and put it in the freezer it will freeze faster because it makes the freezer work harder for a few minutes. I don't know if that is true.

Answer 6

NO! Hot water does not freeze faster than cold water, it just drops temp. faster till it hits a point. If any thing cold water will freeze faster because it is already at a lower starting point than hot water.

Answer 7

I was always told hot water does freeze faster than cold water because of the hot water going from one extreme to the other so fast the temp. drop makes it freeze faster.I know that it makes no real common sense but that is how it works.

Answer 8

Marilyn vos Savant covered this a while back.

Mathematically, it is true that hot water freezes faster.

But there is more evaporation (from hot water than from cold water) prior to freezing, and the freezing is not noticeably faster to the waiting human being. You need the equation to see how it works. Sorry, i don't have that handy.

Also, from my own experience, hot water harms the no-stick coating on some ice cube trays.

there may also be differences based on whether we are talking "pure water" with no chemicals and no ions or tap water.

so you can have smaller ice cubes, minimally faster - or not.

Answer 9

since freezing is the removal of heat from an item to freezing point, I would say that cold water would freeze faster. (remember that refrigerators and freezers are misnomers, they are heat take awayers) Hot water is in an expanded state and if filled the same as cold water will leave smaller cubes. (for simplicity) if a hot water ice cube is going to be smaller, then in theory there is less water.so will not take as long to freeze. (recap) say that your ice cube tray has 12 one ounce holders for water. You fill one with cold water and one with hot water. though it is full, the hot water is expanded so it really does not have the same amount of water as the cold. So the answer is Hot water will freeze faster because of less water.

Answer 10

With the Mpemba Effect, warm water can freeze faster than cold water, under certain conditions. Evaporation, conduction, convection and dissolved gases are possible reasons the effect works. You may have to try different configurations to verify this effect.

Answer 11

i brew a lot of beer and i know from experience that cold water will freeze faster than hot water. it's common sense - assuming all other factors being equal, colder water has less energy to than hot water and will reach freezing more quickly.

if you don't believe me, put two cups of water in the freezer, 1 hot and 1 cold and see which freezes first.