how does warm water freeze faster than cool water?/does warm water freeze faster than cool water?
360729
It doesn't.  The t(exp 4)(temperature difference to the 4th power) law works here.  The higher temperature water will cool faster than the cooler water, however, when it reaches the temperature that the cooler water was in in the first place, it will cool at the same rate the cooler water cooled with.
739180
Warm water is absorbed easier into the body.  Cold water takes longer to absorb, therefore burning more calories.
79685
No.  There was a time when people said it did because some dude in Africa was making ice cream and claimed that his ice cream froze faster if he heated it first, but that's because ice cream needs to congeal, and heating it boiled off much of the water, making it thicker to begin with.\n\nAnd it has been shown even since the time of the Greeks that water that has been boiled prior to freezing will freeze quicker due to the fact that boiling will remove dissolved gases from the liquid, but even that assumes you are comparing water that's been boiled and brought down to temperature versus water that has not been boiled.\n\nBut if you put water that's 8 degrees and water thats 80 degrees in a freezer, the 80 degree water, prior to freezing, will need to reach 8 degrees somewhere between here and there.  All the while, the 8 degree water has made substantial progress towards freezing.\n\nIt is true that hot water loses heat more quickly due to an increased driving force for heat loss, but this is a temporary thing.  As soon as the hotter water reaching the starting temperature of the cooler water, it has no "momentum" in losing heat, but it has lost a lot of time.
662532
Hot water will drop in temperature at a faster rate, but the cold water will freeze first except under certain circumstances in a phenomenon known as the Mpemba Effect\n\nhttp://math.ucr.edu/home/baez/physics/General/hot_water.html for more details on the phenomenon
268388
All water freezes at some temperature. However, pure water can be supercooled below its freezing point if you don't give the ice anything to nucleate around. It will then homogeneously freeze (to very clear ice) below a certain temperature though.
629453
warm water dissolves ice faster than warm air because it can transfer and absorb heat faster than warm air of the same temperature
621743
We cannot make a substance cold. \n\nWe can remove the heat from one place to another.\n\n  What is the difference between ice and water?\n\nFrom ice we have removed heat. The water is water because we have not removed heat from it. \n\nWe should not say ice is cold when compared to water, because we have not made it cold but we have removed heat from it.\n\nSimilarly when we want some hot coffee, we should ask, I want a coffee in which heat is added because we cannot make coffee hot.\n\nThank you.
131139
Absolutely not!! Try it for yourself, with equal amounts of each in the same freezer, in the exact same kind of containers, checking at given time intervals. Use logic, the warm water has to cool down to the temperature of the cold water before it can do anything. The cold water already has the head start!!
656503
It doesn't.  Ice melts more slowly on a colder surface because when ice melts it must draw heat from the surrounding environment, and when there is less heat available it takes longer.\n\n____________\nEdit: as a college science major, I can tell you it simply doesn't work that way.  However, there are a number of factors besides temperature that effect ice melting.  For example, if the piece of ice on the colder block was considerably thinner than the ice on the warmer block the one on the colder block might still melt faster.  In biology, we sometimes melt small amounts of liquid on ice because bad things happen if they get too warm, and two microliters of frozen liquid on ice generally melts faster than ten mililiters in warm (about 98˚F) water.\n\nAnother factor that effects melting point is solutes dissolved in the water before it was frozen.  Salt water freezes at a lower temperature, and consequently melts at a lower temperature, than pure water (that's why the salt the roads in the winter).  If there were a lot of salt dissolved in the piece of ice on the cold block, then depending on the temperatures of the two blocks, the one on the cold block might melt faster.\n\nIt's also possible that one or both pieces of ice weren't water at all.  There are plenty of clear liquids out there that melt at various temperatures.  A compound with a lower freezing point will tend to melt faster, possibly even at a lower temperature.\n\nAnother factor is the starting temperature of the ice.  In one of the biology labs at my school we have a freezer that's at -80˚C, and the normal ones at 4˚C.  If you take a piece of ice out of the -80˚C freezer and one out of the 4˚C freezer, they're both frozen, so they're both ice, but the one at -80 is a lot colder, and is going to take a lot longer to melt, even at a warmer temperature, because it has to warm back up to 0˚C before it can even start to melt.\n\nBut, of course, the obvious explanation is that either your teacher lied to you, or you lost track of which block was which at some point in the demo.
494092
As any sane and decent person would expect, hot water out of the tap will boil faster than cold water out of the tap. However, water that has been boiled once and allowed to cool will boil faster than hot water out of the tap. That's because boiling gets rid of the dissolved oxygen usually found in water, making it easier for the water to boil the second time around.
308806
Consider a liquid (water) and its gas (steam).  To convert water to steam, you first have to heat water to 100 C.  At that point additional energy begins to boil the water.  This is the process where water molecules have enough energy to overcome the attractive force between them (called cohesion, in this case, due to the dipolar attraction between waters).\n\nYou are right in that gases are higher energy (could say hotter), but that's because they've taken the energy from whatever heat source was around when they vaporized.\n\nBack to the water example, water on your skin feels cold because it's absorbing heat from your skin and as the water evaporates, that heat is carried away by the vapor phase molecules (which are moving faster than the liquid form).\n\nThe fast-moving particles from your question have a lot of heat stored, that's why steam at 100 C is more likely to burn your skin than water at 100 C.  It has more heat to transfer.\n\nAs for freon, it depends on which freon you're talking about.  Freon 12 (one of the ones phased out because of ozone depletion) melts at -158 C (Merck Index).
86483
Actually, Gonpatrick, the original question is quite correct: Unlike most substances, water does actually expand when it is cooled, over a narrow temperature range from about 4 degrees C to 0 degrees C (the freezing point.)  This is why water freezes from the top down: the cooler water that is closer to freezing is less dense than, and so floats above, slightly warmer water.  (Above 4 degrees C, water expands when it is heated just like most other substances.) When the water freezes it expands some more, which is why ice floats.\n\nThe reason why it does this has to do with the way water molecules are put together.  The two hydrogens and one oxygen in H2O are assembled in a triangular pattern, with one part of the molecule more positive and the other more negative.  Above 4 degrees C, the molecules move freely around each other, but when it gets close to its freezing temp, the molecules start to align themselves with the positive part of one molecule near the negative part of another, ultimately forming, when it freezes, a hexagonal pattern.  This arrangement takes up more room than when the molecules are free to move around.
745215
The answer is yes. And I bet you want more of an explanation, which gets a little tricky. It would seem evident that cold water would freeze faster than warm water. But there have been raging debates in scientific circles over whether that's true or false. The fact is a lot of different factors contribute to how fast water freezes, including its beginning temperature.\n    Physicists writing in the journal Scientific American have waded into the fray and have probably come the closest to a satisfactory answer. Quoting Paul G. Hewitt in the book Conceptual Physics, the Scientific American writers believe that hot water will freeze faster than lukewarm water, but not faster than cold water. (Except under certain circumstances.)\n    According to Scientific American, water at 90° C will freeze before water that is 60° C. Below 60° C, however, there is a switch and the cooler water will freeze faster. For example, 30° C water will freeze faster than 60° C water. It has to do with the water evaporation of the hot water immersed in a cold environment. The rate of cooling by evaporation is way higher for hot water than for the cooling of lukewarm water.\n    Now, for those certain circumstances. When you put a pan of cold water and a pan of hot water in a freezer (both pans have equal masses of water), the hot water experiences this rapid evaporation AND freezing from below, which cools water on the bottom of the pan. Because the surface water is already warm or hot, the water at the bottom just sits there instead of rising, getting colder and colder. The water at the top experiences evaporation. The combined effect could make the hot water freeze faster than the cold water.
297542
well lets see, if cold water is anything above 0 Centigrade and hot water is anything under boiling....my money is on the hot winning. What I can not understand is why you asked?
664364
There's actually a number of reasons why water does that. Yes, cooler or warmer water can come in and make water differ in temperature in different parts of the body of water. Another reason is that water takes a lot longer to cool or heat than many other things like the earth. The depth of the water makes an impact also. The sun's rays passing through the water faster at different depths heat water when it's not as deep.
480166
If you have an equal volume of hot and cold water the cold water will be heavier.  This is because when you heat up a substance it become less dense, and in general when you cool down a substance it becomes more dense.\n\nThe exception to the rule is water though.  Water is most dense at 3 degrees cesius, after that it start to take a crystalin form and when it freezes actualy expands.  \n\nso long as you are not saying that the cold water is 1 degree and the hot water is 3, then the cold water will be heavier\n\n\nBut remeber it is not by much in any case
419356
I will take a stab at it.  I am guessing it is because water has more degrees of freedom.  In the liquid there is also rotational degrees of freedom to absorb energy that the solid ice does not have.\n\nTo Neil, the formulas are for heat capacity and have nothing to do with the way something is heated, only the amount of energy that it takes.\n\nNor does it have anything to do with Newton's law of cooling.