Why hot water turns to ice faster than cold water?

Question

try it in your freezer, come on guys plz give a brief and an easy answer not like jerdan95 who wrote me a newspaper(OO those people)

Answer 1

Why is it that a pail of hot water set outside in cold water sometimes freezes faster than a similar pail of cold water?

More than one scientist has given the flippant answer "Impossible!" to this question and then been suitably embarrassed after learning that it is possible for hot water in an open container to freeze faster than an identical container of cold water. A more cautious person, Dr. D.G. Osborne of University College at Dar es Salaam, Tanzania, commented on this problem by stating, "No questions should be ridiculed, for everyday events are seldom as simple as they seem and it is dangerous to pass a superficial judgment on what can and cannot happen."

Actually, the question about whether hot water can freeze faster than cold water is an old one. In 1620, the English philosopher Francis Bacon noted, "water slightly warm is more easily frozen than quite cold." Only in recent years has enough been learned about the physics of freezing water to explain this seemingly unlikely phenomenon.

The best explanation I have found is given by Canadian scientist G.S. Kell, writing in the American Journal of Physics in 1969. Dr. Kell presents calculations and experiments which show that an open container of almost-boiling water cooled only by evaporation from the top surface can lose, through evaporation, up to 26% of the original mass of water by the time the remaining 74% turns to ice. That evaporation takes place relatively quickly from the surface of hot water and very slowly from a surface of cold water.

Hence, if one places a wooden or other insulating bucket filled with hot water out in the cold, and places beside it a similar bucket equally filled with cold water, the two will evaporate unequally. By the time both come down to the same temperature, a temperature still above freezing, the bucket originally containing hot water will contain less water than the one originally filled with cold. If the walls of the buckets are vertical, both liquids contained therein still have the same surface area exposed to air; so the rate of evaporation from this time on is essentially the same in both. Since cooling is presumed to continue to be only by evaporation, the bucket with the least water must reach freezing temperature the soonest.

Dr. Kell notes that, if cooling is by evaporation alone, a volume of water starting at near 100°C (the boiling point) will totally freeze in 90% of the time taken by an equal volume at about room temperature.

My experience is that it is pretty hard to make hot water freeze faster than cold. Several tests with metal containers--which, of course, are highly conducting--results in the cold water freezing first. In one instance I was able to freeze the hot water first. To do it, I set two Styrofoam cups in holes carved in a block of Styrofoam to minimize conduction of heat through the cups. Even then, the cold water usually froze first. But when I put water at 19°C (66°F) in one cup and near boiling water in the other and placed them in a freezer at -15°C (5°F), the initially-hot water froze first.

This is the type of experiment anyone in the North can do easily, especially in winter, so there is no reason to take anyone else's word about what happens. If you do attempt the experiment, it is important that equal volumes of hot and cold water be placed in identical containers and that the containers be placed in uniform freezing conditions

Answer 2

Hot Water Ice

Answer 3

Someone says it has been proven hot water freezes faster - where? Prove it. That makes no sense. Its physics. Molecules in warmer water are moving faster than in colder water. Colder water needs to have less energy removed from it (courtesy of the surrounding air in the freezer) than hot water. Therefore, the colder water will freeze faster. As a real life example, look at a contained body of fresh water in the winter, like a lake. When freezing weather first arrives, it takes a long time for the lake to freeze. But, over the course of the winter, when there is a warm spell, you will see the ice melt from the lake. But, if temperatures get below freezing again, the lake freezes over much quicker than it did at the beginning of the winter.

Answer 4

IF this is true, I would say it's because the molecules are moving faster in the hot water.
You see, when water turns to ice it actually takes up more room than it did when it was liquid. This is because of the crystal that water forms. Water forms a crystal consisting of 5 molecules linked together when frozen. These 5 link together in a way that takes up more space than 5 unfrozen molecules.

I would say that since some of the water has already started to form these crystals in ice water perhaps it's harder for the other molecules to find molecules to link to in cold water than in hot water.

It's also possible that your cold water has more impurities in it. Impurities make it difficult for the water to form the crystals. For example... salt. Salt has a property that water likes. I don't remember how it works though. Something like the water ice crystal "wants" another electron or something like that, and the salt has an "extra" electron, but in order for the ice crystal to accept that electron in the salt crystal it has to break itself apart. So basically the ice crystal melts itself in order to attach to the salt, at which point the water can no longer reform back into the crystal because the salt molecule won't fit. THAT'S why we put salt on ice and it melts.

Answer 5

Warm water freezing faster than cold water is technically referred to as the Mpemba effect.

One theory is that it is due to dissolved gasses, but this cannot be demonstrated by predictive theoretical computations.

The warm water clears out dissolved gasses more quickly from within the water and also can hold less gasses than cooler water.

The dissolved gasses in the water may tend to slightly slow down the freezing process as the warmth of the water causes the gasses to dissipate into the surrounding air faster causing the warm water to freeze a little faster than cold water.

But other explanations are possible. It's exact cause is still not totally understood.

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

for a better explanation.

Answer 6

Thats a false urban legend. When this theory was tested the results concluded that the cold water froze faster. The only exception is if you throw boiling water into the air when its below 0 degrees outside. The water will turn into ice before it hits the ground. This is simply because the water molecules are very active and because they are spread apart, it makes it easier for the cold air to surround the molecules.

Answer 7

Hot water turns to ice faster than cold water? Never heard of it.

But if this is true when you put it in your freezer, this phenomenon is probably caused by your freezer.

Answer 8

it does not old wife's tale based on misunderstood science fact HOT WATER COOLS FASTER than cold water ( the greater the temperature differential the faster the heat flow ( basic physics) somehow LOSES HEAT FASTER turned into FREEZES FASTER if you don't believe then TRY IT--------------------HEY JERDIN your results were invalid unless you can show that the freezer had a uniform temperature that's why experiments are done in controlled condition your other example agreed with my answer on water now water vapor and steam do odd things due to evaporative effects

Answer 9

I'm not a science person..but it is quite obvious...if you put hot water in the freezer the freezer works harder to maintain its temp. Therefore it freezes faster.. if you put cold water in..the freezer does not feel the heat and does not work harder. Just like your thermostat....when you first turn on the air conditioner it works really hard to get rid of the heat...then it kicks off when it is at the set temp. then it goes at a steady pace and it may turn off for a while.. when it drops a degree it comes on again and keeps its pace to keep the house at a steady temp.. homostasius!!!! duh

Answer 10

The laws of motion & thermodynamics meet in the answer to this question. Change in temperature is a result of atomic or molecular movement. Heat moves in the direction of a lower temperature. When you touch ice, the heat moves from your body to the ice. Thus you "feel" not the cold of the ice, but the heat leaving your own body.

Since a body in motion tends to remain in motion, when you take into account the acceleration of motion from hot to cold (as opposed to from cool to cold) you can see how the increasing speed of movement from hot to cold would lead to an incrementally faster rate of freezing.