Does hot water freeze faster than cold water?

Similar questions: hot water freeze faster cold.

In many situations, hot water does indeed freeze faster than cold water. According to the NOBLE website: Does Hot Water Freeze Faster Than Cold? This question, first raised in 1969 by a Tanzanian student named Erasto Mpemba is still a topic for controversy today.

When a container of water is placed in a freezer, there are many factors which can affect the length of time it will take to freeze, and under the proper combination of circumstances, a given volume of hot water in a container may freeze faster than the same volume of cold water. Some factors which can contribute to this phenomenon are: Evaporation: Hot water is more likely to evaporate from a container than cold water, leaving a reduced volume of water in the container. Less water takes less time to freeze.

Also, the evaporating water it pulls heat from the water remaining in the container, reducing its temperature and thus its freezing time. Conduction: When a container of hot water is placed on an icy surface in a freezer, the hot container will melt the ice on the surface. The melted freezer ice will provide better thermal contact with the hot container, allowing better conduction of heat from the hot container than from the cold container placed in the same environment.

Convection: Water is most dense at 4C. When a container of uniformly cold water freezes, it generally forms a skin of ice, which is less dense, on the surface. This skin insulates the remaining volume of water, impeding heat loss.In the container of hot water, as the surface water cools to 4C, it is more dense than the hot water below, and sinks, forcing more hot water to the surface to be cooled.

This sets up convection currents which can cause the container of hot water to lose heat more rapidly than the container of cold water. Impurities: Water usually contains impurities such as dissolved gases, dust particles, etc.These impurities can lower the freezing temperature of the water, and also provide nucleation points which cause ice crystals to form. Some of these impurities are driven out when water is heated.

The purer hot water may actually have a higher freezing temperature than the cold water, and it may also be subject to supercooling. When this occurs, the entire volume of water remains liquid below its freezing point, then the entire volume freezes solid rapidly. The cold water may tend to form ice crystals on the impurities, insulating the remaining water in the container, and there may ultimately be some liquid water in the container when the formerly hot container has frozen solid.

It is important to remember that in an experiment such as this, a great many factors come into play, many of them quite subtle, and initial conditions are crucial in determining the outcome. And, if you want to impress your friends with a really cool word, you'll want to learn about the Mpemba effect. In an article written by Monwhea Jeng of the Department of Physics, University of California 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. Sources: http://www.noblenet.org/, http://math.ucr.edu/home/baez/physics/index.html Zora's Recommendations How Things Work: The Physics of Everyday Life Amazon List Price: $68.95 Used from: $47.04 Average Customer Rating: 5.0 out of 5 (based on 6 reviews) Experiments in Modern Physics, Second Edition Amazon List Price: $88.95 Used from: $63.15 Average Customer Rating: 4.0 out of 5 (based on 2 reviews) Janice VanCleave's Physics for Every Kid: 101 Easy Experiments in Motion, Heat, Light, Machines, and Sound (Science for Every Kid Series) Amazon List Price: $12.95 Used from: $2.95 Average Customer Rating: 4.0 out of 5 (based on 4 reviews) If you're interested in science experiments and how and why things work, you might like some of these titles.

Sometimes, depends on the temp of the cooler water, for one thing. 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....see link Sources: math.ucr.edu/home/baez/physics/General/h... .

Yes, but not always It does depend on the temperature differences between the water samples being considered. If one of the samples is very close to boiling and the other very close to freezing, the colder water will freeze faster. However, the phenomenon does occur very regularly.

The article referenced below provides a very detailed explanation of the effect. The cause that seems to hold the most relevence to me is convection. I studied chemical engienering in school and you learn that heat is transfered most effectively across a medium when the temperature gradient is very high.

Therefore, the water will begin to form small temperature gradients within the liquid itself, which will transfer heat more effectively even as it starts to cool. math.ucr.edu/home/baez/physics/General/h..." rel="nofollow">math.ucr.edu/home/baez/physics/General/h... Sources: math.ucr.edu/home/baez/physics/General/h..." rel="nofollow">math.ucr.edu/home/baez/physics/General/h... .

Nope Needless to say, I conducted my research in the calm and systematic manner that has long been the trademark of Straight Dope Labs. First, I finished off a half a pint of Haagen-Dazs I found in the fridge, in order to keep my brain supplied with vital nutrients. Then I carefully measured a whole passel of water into the Straight Dope tea kettle and boiled it for about five minutes.

This was so I could compare the freezing rate of boiled H20 with that of regular hot water from the tap. (Somehow I had the idea that water that had been boiled would freeze faster. )Finally I put equal quantities of each type into trays in the freezer, checked the temp (125 degrees Fahrenheit all around), and sat back to wait, timing the process with my brand new Swatch watch, whose precision and smart styling have made it the number one choice of scientists the world over.

I subsequently did the same with two trays of cold water, which had been chilled down to a starting temperature of 38 degrees. The results? The cold water froze about 10 or 15 minutes faster than the hot water, and there was no detectable difference between the boiled water and the other kind.

Another old wives' tale thus emphatically bites the dust. Science marches on. AN ANOMALOUS SITUATION ARISESDear Cecil:Just a few days after I read your column on whether hot water freezes faster than cold water (you said it didn't), I happened to come across an article in Scientific American entitled "Hot Water Freezes Faster Than Cold Water.

Why Does It Do So? " What gives? I hope we will see another column soon resolving the issue.

--Ellen C. , ChicagoDear Ellen:I know it must unnerve you to find that a supposedly infallible source of wisdom can make mistakes, so let me hasten to reassure you: Scientific American did not screw up. My results and theirs (specifically, those of Jearl Walker, author of SA's "Amateur Scientist" column) are consistent--we were just working in different temperature ranges.

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. Jearl, 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. )Jearl 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. In 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. Fascinating 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. Sources: http://www.straightdope.com/classics/a2_098b .

1 I should probably note that it also depends on the volume of water and shape of container. Shallow water will freeze faster if cold, which further reinforces the idea (at least in my mind) that the phenomenon occurs due to convection. Freezing water in ice cube trays (shallow water) doesn't exactly debunk this phenomenon.

I should probably note that it also depends on the volume of water and shape of container. Shallow water will freeze faster if cold, which further reinforces the idea (at least in my mind) that the phenomenon occurs due to convection. Freezing water in ice cube trays (shallow water) doesn't exactly debunk this phenomenon.

" "I am looking for a connector to attach to a cold water faucet and a hot water faucet together (for my bathroom sink). " "Why does it take more hot water to warm up a bath than cold water to cool it down?" "Which is faster, hot or cold? " "Does hot water freeze faster.

Were is the valve that conyrols hot and cold water in the tub.

As the water temperature increases in my hot tub, does the temperature actually rise at a faster rate than when cold.

I am looking for a connector to attach to a cold water faucet and a hot water faucet together (for my bathroom sink).

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.