What would freeze first?

Question

If you put a glass of hot water and a glass of cold water into the freezer at the same time with same amounts and same containers, which would be the first to reach freezing point?

Answer 1

Strangely enough, the HOT water would freeze first. There is a chemical explanation for this.

Answer 2

The phenomenon that hot water may freeze faster than cold is often called the Mpemba effect. Because, no doubt, most readers are extremely skeptical at this point, we should begin by stating precisely what we mean by the Mpemba effect. We start with two containers of water, which are identical in shape, and which hold identical amounts of water. The only difference between the two is that the water in one is at a higher (uniform) temperature than the water in the other. Now we cool both containers, using the exact same cooling process for each container. Under some conditions the initially warmer water will freeze first. If this occurs, we have seen the Mpemba effect. Of course, the initially warmer water will not freeze before the initially cooler water for all initial conditions. If the hot water starts at 99.9° C, and the cold water at 0.01° C, then clearly under those circumstances, the initially cooler water will freeze first. However, under some conditions the initially warmer water will freeze first -- if that happens, you have seen the Mpemba effect. But you will not see the Mpemba effect for just any initial temperatures, container shapes, or cooling conditions.

Answer 3

I am surprised, but the readings say hot water

The phenomenon that hot water may freeze faster than cold is often called the Mpemba effect. Because, no doubt, most readers are extremely skeptical at this point, we should begin by stating precisely what we mean by the Mpemba effect. We start with two containers of water, which are identical in shape, and which hold identical amounts of water. The only difference between the two is that the water in one is at a higher (uniform) temperature than the water in the other. Now we cool both containers, using the exact same cooling process for each container. Under some conditions the initially warmer water will freeze first. If this occurs, we have seen the Mpemba effect. Of course, the initially warmer water will not freeze before the initially cooler water for all initial conditions. If the hot water starts at 99.9° C, and the cold water at 0.01° C, then clearly under those circumstances, the initially cooler water will freeze first. However, under some conditions the initially warmer water will freeze first -- if that happens, you have seen the Mpemba effect. But you will not see the Mpemba effect for just any initial temperatures, container shapes, or cooling conditions.

Answer 4

cold water of course

to freeze water, you need to
- first, cool the water to zero
- then, extract even more heat so that it can change state

the first bit depends only on the amount of water, and the temperature difference (all else being equal, such as diluted minerals, etc)

if you've got hot water at, say, 70 C and want to take it to 0 that's a 70 degree difference, whereas in the case of cold water at, say 10C that's just a 10 degree difference. So your glass of cold water will, say, need to lose 1/7th of the heat the glass of warm water will need to lose

of course the warm water will initially cool faster, on a degree per hour basis, because it has a bigger temperature difference with that of the air in your freezer. But the difference in pace will diminish and it will still come out a good deal late.

then, both need to freeze. the cold water will get there first. and it will take time to freeze fully, because the that amount ot heat that water needs to release in order to freeze, is nearly 80 times larger than that it needs to cool by 1 degree C

so it is quite likely that, at some point, you'll have the (ex-)cold glass of water partly froze, and the (ex-)hot glass of water partly frozen also

which could lead an unprepared mind to believe that it didn't make any difference that one glass was hot to start with (hence the urban myth that hot water freezes faster). But this is wrong, and the glass of cold water will still have totally frozen first

hope this helps

Answer 5

There are many other factors which have to be considered.
1. Shape and material of the containers
2. Distance between the two containers

The cold water will freeze first, if the containers are kept at a distance from each other and the containers are closed with a lid.

Both the containers will freeze at the same time if they are kept very close to each other and the containers have no lid.

Answer 6

It's on of those quirks of science that the hot water will freeze first.

As for why, nobody's really sure. The are loads of theories out there, a quick google search should give you a good snapshot.

My money is on the theory that the hot water can effectively 'freeze' at a higher temperature than the regular freezing point. The latent heat of freezing isn't converted into heat, but radiated out. Of course there's still the problem of HOW that happens, but we'll solve that riddle once we've worked this one out.

Answer 7

the cold water will freeze first because its temperature when you put it on the freezer is low . and the freezer will make it much lower so it will freeze first than the hot water

Answer 8

If you mean same amount as same mass, cold water will freeze first definitely. As hot is a perceived quality, and how hot is not mentioned, and if same amount means same volume, and hotness may refer to less mass at same volume, you could guess much but my vote will still be to cold water.

Answer 9

Glass of hot water. This is because for evaporation lot of heat from surrounding will be taken up and result in additional cooling!
Cold water on other hand has high latent heat of fusion.

Answer 10

Hey thenks Torskie for the explanation until now I would say that the cold water would freez first. ten points should go to you.