Why does hot water freeze quicker than cold water when placed in a freezer???
 

Hey there...I just learned that placing hot water in a freezer will freeze faster than placing cold water in a freezer...is this true??? If so then why is that so??? I would think that cold water would freeze quicker since it's closer to the freezing point than the hot water...plz give me info on this...THANX
C'YA ?:-D

EDIT: OK...now that it has been determined that hot water freezes faster than cold water...I have another question...why don't freezers use hot (or at least warm) water than cold water...ice cubes take too damn long to make...they need to make em faster...maybe they could at least use a setting or something

Ummm, no.

The transition phase of any substance, in this case, the transition of liquid H2O to solid H2O, involves removing molecular energy from the substance (i.e. heat). If a substance starts with more heat energy, it naturally will take longer to remove that energy than an equal mass of the same substance with less heat energy given an equal cooling rate.

This can be easily shown by the fact that both substances will have a given amount A of heat energy to radiate while the second substance will have A + B amounts to radiate.

Actually, Lebell, I hate to disagree with you, but:

Yes, it does. And here is why:

Taken from http://math.ucr.edu/home/baez/physic...hot_water.html
The rest of the article discusses experiments done, the possible causes for this phenomena, and much more.

It's funny this question was asked here because we had just been discussing this at work with some of the students.

Well dang.

I guess today is a good day; I learned something new.

Thanks JD!

Could it be one of those strange hydrogen bonding phenomenons? It's been awhile since I did any series chemistry so I'm not going to conjecture any further than that, but that little hydrogen bond there in water makes for some odd properties. My favorite is the greater density as a liquid than a solid.

Perhaps, in some circumstances, it is easier to get the cooling process going in warm water and more difficult in others. Kind of like pushing a weight down an incline. One with the top half coated in sand paper and the bottom half in teflon vs another incline with the top half made of plastic and the bottom in teflon. It would be far easier to get the weight on the plastic moving toward the teflon than the one on the sandpaper. Once they reach the teflon they both travel at the same rate but the one that started on plastic has a head start.

That is probably why they use hot water on the back of a Zamboni.

Back in the real world: ;)

So what shape do I need to make my ice-cube tray? And what temperature water should I put in it? I need a gin and tonic, quickly...

It has everything to do with H-H bonding. As strange as it is .. energy is required for polar water molecules to form a lattice structure. Screwed up .. but true!

Here's an aside: did you know that when it rains, the air temperature actially increases? This is due to the breaking of H-H bonds as the water falls. Engery released is in the form of heat.

Odd .. but true!

God of Thunder, the reason why they use hot water in zambonis is because the hot water melts the top layer of ice creating not just a layer of new ice, but making the rink a solid block. Some of the scratches that skates put in ice cannot be covered well unless the ice is remelted, so that is the zambonis job.

/hockey nut

Actually I believe that the hot water is used to melt the top layer of existing ice and allow the newer, warmer water combine and form a more solid composition. You wouldn't want sections of ice flaking off because they didn't bond right to the previous surface.

The normal rectangular shape should work and you want your water warm-hot from the tap or heated from bottled water.
If I'm not mistaken, some companies make a hot-water dispenser to sit with the cool-water dispenser.

Here's my theory on the whole thing:

the hot water cools at a more rapid rate due to it trying to cool the environment around it. the cold water is so close to the freezing point to begin with that it does it slower.

This is much the way our hands get cold handling object during the winter time. Our hands are losing heat by trying to warm the object they are holding. There's a specific term for this but I can't remember it right now.

<i>"Of course, the initially warmer water will not freeze before the initially cooler water for all initial conditions."</i>

If a specific result does not happen in <i>all</i> tested , controlled conditions, then scientifically speaking - nothing has been proven.

But of course - I have no personal stake in this - I drink my beer cold, and my wine at room temperature. Beyond that, my quest for knowledge ends.

I am gonna try this out..And if it works for me, I am gonna be making some bets with alot of people.

Initially, I thought bull. But, here are some good explanations for why this may occur.

http://www.newscientist.com/lastword...e.jsp?id=lw236

From what I can remember, there are a few things to keep in mind.

Hot water is more willing to give off it's heat due to vapor pressure of the increased temperature. Every time you see water giving off 'steam/vapor' it is in effect cooling istself to reach an equlibrium. (with the room temp)

2nd, hot water has less dissolved gas than cold water. You can easlily illustrate this point by taking 2 20oz bottles of diet coke. Place one of them in the very back bottom of your fridge. Place the other on on top, outside the fridge. After 24 hours gather the warm and cold bottles and open them. You will notice a LOUD pffffffft comming from the warm bottle, and you will notice barely any from the one that was in the fridge. The colder the water the more readily it can hold dissolved gasses. The warm bottle of pop can't hold as much dissolved gas, at room temp or higher it is super saturated, though it can hold it in suspension due to the pressure inside the sealed bottle. As soon as you open the bottle you are equalizing the pressure between the liquids surface and the surrounding atmosphere.

So, as I digress...

...disolved gas in a water impeded the 'hydrogren-bonding' involved with the freezing process. You can do another simple experiment to see the difference. If you were to take a cup of water and boil it in the microwave and take a cup of water directly out of the tap and freeze them both, you will notice that the one that came from the tap will be cloudy. Whereas the cup of water that you boiled will be almost crystal-clear. The couldiness is the dissolved gasses that impeaded in the hydrogen bonding as the water molecules crystalized during the freezing process. (The clear ice is stronger, the cloudy ice will have a tendency to cleave if stressed)

So overall, the hotter water will freeze faster than the cold water due to both the rapid energy lost due to the decreased vapor pressure as well as the lack of dissolved gasses.

;)

-SF

I've always wondered by it seems warm when there it is snowing out compared to other cold days in winter, I thought it might have been since clouds were trapping heat or that I just felt happy that it was snowing but I supposed what you said about it heating up when it rains also applies to snowfall.

I always thought that the heat from the hot water in the ice tray triggered the thermostat sensor in the freezer causing the freon pump to run, the freezer to get colder, and then the water freezes faster from the harder working freezing apparatus. But the dissolved gas thing makes sense, too.

Vermin, your unscientific theory was so cool since no scientist would have liked it, or even come up with it! Common sense thinking.

But my senses are even more common. Guys, broaden your minds a bit. Naturally this has its explanation in that when as soon these tests are done, one alien says to another "look at that kindergarten science - I just have to screw with them and freeze the hot water. Makes me laugh every time! Irk irk irk irk..."

if u want ice to freeze extra fast add tiny bits of ice to them bc the real thing that slows the freezing isnt getting it to the right temperature its begining the crystalization thats why phenominons like hypercooling happen where somthing cools below its freezing point befor it begins to freeze it has no crystals to modle itself after. Id like to thank either 10th or 11th grade science for that one

I always just though the hot water evaporated out so now there was less to freeze. I never was too bright though.

I'm geussing that the energy transfer results in a greater loss of energy in hot water than in cooler water, so that the hot will lose it's heat faster and as a result spread the effect more quickly throughout itself speeding up the process of freezing to such a rate that it far exceeds that of the cool water. I hope that made some sense.

What does it mean Basil?

Lead is an odorless, tasteless, soft, gray metal. On exposure to air, lead is rapidly covered with a film of oxide, hydroxide, and carbonate. Similarly, when lead is exposed to water with dissolved oxygen, lead hydroxide, sulfate and carbonate are formed. A small amount of the salts then pass into solution. Lead salts are found in air, food, household dust and soil. If ingested or inhaled over a period of time, lead and its salts may cause serious internal damage such as impaired kidneys, nervoussystem and red blood cells. Particularly susceptible to the toxic metal or salts aresmall children.

Lead gets into the drinking water through the use of lead-containing pipes, solder, brass and chrome-plated faucets. The homes most likely to have a lead problem are older houses with lead pipes and homes with lead service lines.

The hotter the water the more soluble it is, thus hot tap water has the chance to cary more deposits.

When being heated, organic compounds in water, such as iron or manganese, can oxidize; this oxidation has the potential to cause discoloring or an off taste.

While this depends entirely on the tap water. I myself don't feel the need to save five minutes boiling water by using hot tap water, at the expense of even a slight change in taste. Or an off chance risk of health.

While something like boiling an egg probably won't matter. Some say it does in delicate foods like pastas.

my 2 cent

Quote:

:While this depends entirely on the tap water. I myself don't feel the need to save five minutes boiling water by using hot tap water, at the expense of even a slight change in taste. Or an off chance risk of health."

Boiling water to turn around and freeze it is an extreme.

There is even a difference between 60F water and 120F water and the time that it takes them to freeze. (Tap v. Hot Tap)

-SF

Hundred-Peons,

I'd make sure that you credit the author of your word-for-word cut and paste job. You never know who will defend their copyright.

http://www.rohmhaas.com/company/plab...fdocs/lead.pdf

-SF

that was way cool, intersting and informative....thanx!

I'd like to thank Kurt Vonnegut's concept of Ice-9 for making that concept incredibly easy to understand.

I dont the true answer, but it always made sense in my mind that, since water was the only molecule whose volume actually expands when in solid form...that since the molecules are farther away when warmer, the ice would not have to spend as much energy to move them apart....that being said, as I type this, it seems silly.

lol

There's a good demonstration of this you can try in the middle of winter if you live in a really cold place. It has to be REALLY cold to pull this off - we're talkin' 15, 20 below. Get a pitcher full of cold water and throw it outside. Then do the same thing with a pitcher of hot water. Notice how the hot water doesn't even hit the ground? It just explodes in a cloud of steam. This is because it's freezing instantly, whereas the cold water is not.

Reason behind it is the same as in the freezer - greater surface area due to the expansion of the molecules.

Hey, this shall settle the arguement! ;)

-SF

http://www.lsbu.ac.uk/water/explan.html (Go to #31)

http://www.school-for-champions.com/science/mpemba.htm

The top one is scientific, where the bottom one is more of a guide to recreate the experiment.

So what Saltfishes link is saying is that hot water appears to freeze first because of the temperature differntials, but it will not actually become solid ice faster, but slower. So if you want to say create ice cubes, use cold water because it will form solid ice quicker. Less ice is formed by hot water in the same period of time, it just appears first. So no, hot water does not actually freeze faster, it just appears to. Don't let appearances get in the way of logic.

I think what saltfish's article is saying is that, during the supercooled timeperiod, the water remains in the liquid state. This is what supercooling is. According to the graph, the supercool state for hot water is much shorter than for cold water, therefore the hot water will become a solid once equilibrium has been reached at the freezing point. It is also asserted that this is assisted by dissolved gases in hotter water, as nucleation will bring any supercooled substance out of the supercooled state very quickly.

http://www.lsbu.ac.uk/water/images/mpemba.gif

So, at the end of the day, assuming nucleation is the same in both situations (or no nucleation at all,) Hot water truly does become a solid faster.