why is it that hot water freezes faster than cold water put in a freezer at the same tjme?

Answer 1

Hot water can in fact freeze faster than cold water for a wide range of experimental conditions. This phenomenon is extremely counter- intuitive, and surprising even to most scientists, but it is in fact real. It has been seen and studied in numerous experiments. While this phenomenon has been known for centuries, and was described by Aristotle, Bacon, and Descartes [1-3], it was not introduced to the modern scientific community until 1969, by a Tanzanian high school student named Mpemba.

Answer 2

Water has some very interesting properties. Basically you will find that particles of hot water are more distantly spaced than those of water which is say at room temperature.

This small feature causes water to exhibit an anomalous behaviour when exposed to an enviroment which tends to try to change its state. Take this classic example; any liquid would flow easily in to a porous wall. Hot water is like a porous wall i.e. with its molecules floating about loosely.

Tiny bits of frozen water moecules floating about in the freezer attach themselves far much easier on to a hot water surface than on to a cold water surface possibly due to opposite forces being exhibited by the contents in question and the porous nature of hot water surface. These tiny bits escape fast in to the hot water in a competitive fashion with each one trying to absorb the other so as to change its state and thus hot water being smaller in mass and contained in the freezer will be overcomed faster and freeze

I hope this helps...

Answer 3

It doesn't...that's an old wive's tale. However, if you first boil water, then let it cool down to room temperature and put it into the freezer with room temperature water straight from the tap, it will actuall freeze a little faster due to the fact that the air dissolved in the water comes out during the boiling process.

Answer 4

Never seen this happen but I am off to the freezer to try it :)

I am guessing that if equal volumes of hot and cold water are placed in the freezer

As mentioned in a previous answer the hot water begins to evaporate into the freezer , hence the volume of hot water decrease. By the time it gets to being cold water there is a lot less of it.

Answer 5

Does it? There's something logically wrong with your statement. If you put hot water into a freezer, then as it cools down to freeze it must first of all become cold water. Then this cold water must take the same additional amount of time to freeze as fresh cold water put into the freezer. So the total amount of time for the hot water must be greater.
Am I missing something?

Answer 6

Someone has already hit the nail on the head. It's not hot water that cools quicker but water that has been pre-boiled.

The boiling process removes some of the mineral content of the water as these tend to precipitate (e.g., Calcium carbonate forming limescale)

This raises the freezing temperature of the water closer to zero. Without boiling, the mineral content of the water actually means that the temperature must be reduced below zero to get ice forming.

TI expect the difference is minimal but in areas with high mineral content in their water it may be more pronounced.

Answer 7

It does happen, and the reason is that hotter things lose heat faster than colder things do. You can prove this in other ways too - for instance a cup of hot water will cool to room temperature faster than a cup of luke warm water in the same time - try it with two cups of water and two thermocouples connected to an electronic thermometer.

Answer 8

Im not really sure abou t this one, but I know that when particles are heated they break apart and when they are cooled they come together. like when you boil water steem comes up because the particles become light.

So when you put hot water in the freezer, my theory is: the particles are already loose and can therefore come back together very quickly
and in waters normal form the particals arent as loose.

I have read the link given by the first answer and i think my theory is wrong:)

Answer 9

As the hot water evaporates it will loose heat faster than the cold water and so freeze quicker

Answer 10

Is it anything to do with the freezer thermostat detects a higher temperature rise and the coolant motor works for longer then it needs to to bring the temperature down to a level where the thermostat says stop?