Is it true that hot water freezes faster that cold???
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.
635448
For Fastest Speed, Hot water\nFor safer method, cold water
509639
the cold water cools down the hot water, and the hot water warms up the cold water until they are at the same temperature....lukewarm 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.
893761
Using the particle theory of matter, the movement of particles in any matter (i.e. one that has mass and occupies space) increases (i.e. particle speed increases) with its temperature.\n\nWarm water has a higher a temperature than cold water.  Hence, the particles in the warm water move at higher speeds than that in cold water.  Moving at higher speed means having greater kinetic energy.  Thus, easier for the particles to break the inter-molecular forces present among the particles in the liquid to travel into the air.\n\nBy the way, this question should have been placed under the physics field.
461446
I found that cold water (38 degrees Fahrenheit) froze faster than hot water out of the tap (125 degrees F). I chose these two temperatures because (1) they were pretty much what the average amateur ice-cube maker would have readily available and (2) I couldn't find a mercury thermometer that went higher than 125 degrees.\n\nJearl, who is not afflicted with penny-pinching editors like some of the rest of us, was able to get his mitts on a thermocouple that could measure as high as the boiling point, 212 degrees F. He found that water heated to, say, 195 degrees would freeze three to ten minutes faster than water at 140-175 degrees. (There were differences depending on how much water was used, where the thermocouple was placed, and so on.) \n\nJearl suggested that the most likely explanation for this was evaporation: when water cools down from near boiling to the freezing point, as much as 16 percent evaporates away, compared to 7 percent for water at 160 degrees. The smaller the amount of water, of course, the faster it freezes. \n\nIn addition, the water vapor carries away a certain amount of heat. To test this theory, Jearl covered his lab beaker with Saran Wrap to prevent water vapor from escaping. The freezing rate difference was greatly diminished. Conceivably convection (motion within the water) also plays a role.\n\nFascinating as all this no doubt is, all it basically proves is that very hot water freezes more slowly than very VERY hot water. The ordinary fumbler in the fridge, on the other hand, is dealing with temps more like the ones I was measuring, in which case cold freezes faster than hot. I rest my case.
888554
Strangely enough, the HOT water would freeze first.  There is a chemical explanation for this.
238723
Because it's the only way to determine the veracity of a hypothesis.  The reason crackpot theories exist is because no one tests them.  I know people today who think that hot water will freeze faster than cold, even though common sense will tell you that the refrigerator will need to remove heat from the hot water to reach the same state as that of a tray of cold water.  Simple research will find that hypothesis is not true.
323207
You could test whether or not salt really does make water freeze more slowly or boil more quickly. Just get four containers of water--two for boiling and two for freezing--and a thermometer. \n\nWith one of the containers without salt, put a thermometer in it and boil and time how long it takes. Mark the boiling point temperature and time. \n\nDo the same thing but one of your containers with salt. Compare your temperatures and times.\n\nThen, you can do the same two steps with freezing with the other two containers.\n\nIf you wanted to get really crazy, you could test to see whether a lot of salt vs. a little amount of salt makes a difference. Or, if you wanted to tone it down, you could do only one--the boiling or the freezing. \n\nThis seems to me like concepts that a second grader could handle.\n\nGood luck!
338330
The answer to this is made tougher by the fact that the water will be freezing.  I mean how can you answer a question where the water is ice cold and use the data provided at STP?  Think you need to either re-read your question or provide a little more info.
408269
It actually can be, believe it or not.  It has to do with hydrogen bonds.  Water exhibits very strong hydrogen bonding due to its polarity, and in order to freeze, these hydrogen bonds in liquid water must be broken.  In hot water, more of these bonds are already broken, so a quick drop in temperature could allow the water to freeze before the hydrogen bonds reform.\n\nNote that this is strictly a kinetic or time-based effect.  Thermodynamics dictates that cold water will freeze faster since a smaller energy drop is required, but in some cases it is entropically favored for hot water to freeze faster.\n\nAlso note that stirring the water vigorously will also break hyrdogen bonds, so stirred cold water will almost always freeze before stirred hot water.  You will only observe the phenomenon of interest when the water is fairly pure and undisturbed, and the temperature drop is rapid enough.\n\nWe discussed this very problem in my graduate-level thermodynamics class.
22699
Yes, but not a significant amount.  When you drink ice cold water, your body uses energy and burns calories to bring the water up to your normal body temperature.  Check out the source link for more detail into exactly how this works.
825292
i guess I'm wrong   but I thought that water would  freeze at 0  degrees celsius.  also it would boil at 100 degrees C. Even in a vacuum.  my guess!  btw at absolute 0  kelvin,  does that only exist in a vacuum?  If we could reach  - 450 degrees F.  would our cpu's operate at an infinite speed.....got me on this one.  I'm not sure on how atmospheric pressure relates to these conditions.  But I know someone knows!
714260
only if you put the hot water in a colder system than what you put the cold water into
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.
926439
fresh water freezes faster...ps, i gave you best answer on a question
734492
Heat = mass x specific heat of material x change of temperature.\nSpecific heat of water is 1. So the amount of heat needed to be added is the mass of the water x the amount of change needed to get to boiling. So cold water does not boil faster. \n\nsalt will cause it to take longer. \n\nPeople think that tea tastes betterr if you start with cold water, which holds more oxygen. As you heat the water, the oxygen comes out. This may look like boiling.