How Ice Melts

Killer Instinct writes "Ever wonder how ice melts? Until now, scientists could not explain why ice cubes in your drink melt. They've known the basics, but the details remained elusive. A breakthrough new study, announced yesterday, supports a leading theory that melting starts when the fundamental structure of matter begins to crack. Melting is considered a basic phenomenon in physics. An understanding of how it works is crucial to gaining a firm grasp on the physical world."

Hmmmmm...

Ever wonder how ice melts?

No.

Re:Hmmmmm...

I didn't read the full article earlier, was this one of the top 125 Big Science questions?

Re:Hmmmmm...

That's a shame. This is a very interesting topic. We've known for centuries that melting is related to heat, and there are molecular models of freezing. Namely, water molecules tend to align themselves in a crystalline structure unless they're stirred up. A region freezes when the average kinetic energy is low enough for the molecules to align themselves. Consider a fairly large volume of water -- in macroscopic scales. Heat conduction through liquid water is faster than through ice, because of convection. So the macroscopic freezing process isn't reversible. (There are other reasons why the process isn't reversible, but one suffices)

This means that a different process is responsible for macroscopic melting. Since macroscopic chunks of ice tend to be imperfect crystals, it stands to reason that the weak unions between crystalline structures facillitate melting.

Re:Hmmmmm...

This could have all sorts of ramifications in materials science. If a good model for macroscopic melting is found, we might be able to design processes to alloy metals much more resistant to heat than are currently possible, for instance.

Re:Hmmmmm...

An understanding of how it works is crucial to gaining a firm grasp on the physical world.

Really? I don't really understand it and I seem to be able to grasp objects just fine.

Anti-Cold

Ever wonder how ice melts?

Not really. But I have a hypothesis that it has something to do with heat or as I call it, "anti-cold." There seems to be a relationship between 0 degrees Celsius and ice melting. Likewise a relationship with 100 degrees Celsius and water boiling (when under one atmosphere of pressure). There must be some underlying mathematical connection; for these events and their temperatures surely can not be coincidence. Some day I will solve this mystery, but only when I am properly funded by government grants.

Re:Anti-Cold

"Not really. But I have a hypothesis that it has something to do with heat or as I call it, "anti-cold."

I like how people bitch about the lack of 'news for nerds' on this site lately. Then, when something comes along that's truely nerd worthy, everybody becomes a smart ass.

Re:Anti-Cold

If you don't think that matters, then you certainly don't qualify as a "nerd". :P Basic science is all about finding out how the world works, without necessarily having any obvious utility for that knowledge. A couple of days ago was the 100th anniversary of Einstein's publication of the theory of special relativity. Did that "matter" at the time?

Re:Anti-Cold

The real reason of course, which you wouldn't know from reading the pseudo-scientific raving of the parent poster, is that melting is an adaptive response to a changing environment.

You see, most water was burned at an earlier time. So, when it encounters heat it melts out of fear! It melts to more effectively evade what it expects might be a dangerous encounter. This also explains why water melts faster when it is shaken upside-down and verbally threatened.

Some people think that this proves that water is less-than-rational, however it's clear to me that it is an adaptive response. The kind of therapy that would get it out of that kind of feedback loop is much to expensive for most water to afford, anyway. Most people don't realize that there are whole water galaxies, where water can more easily acheive economic unanimity.

This simple theory explains so much evidence. Why do we see so little water inside of volcanoes? Inside of airplane engines? Or inside of stoves? It's because water fears heat! Based on an earlier, traumatic reaction that must have occurred sometime in its past.

I'll be here waiting for my Nobel Prize. Is the king of Sweden's daughter hot? Prolly.

Re:Not Insightful or Interesting

Actually, the original value for freezing in the Centigrade scale was 100 and boiling was zero. It wasn't changed until the mid 1700's.

While what you're saying is true, I think that the way you put it may give people reason to exaggerate the life span of the original scale. The original system was proposed in 1742, and modified to its current version in 1747. Both are years I'd say qualify for the being part of "the mid 1700's".

Reference [wikipedia.org].

It's about time...

I can finally sleep at night!

Not suprising

This is somewhat akin to boiling really, at least from my perspective.. small nucleation points, that spread throughout the liquid or crystal, effecting an overall phase change when the energy distribution reaches a point such that the majority of atoms prefer the gaseous or liquid state (depending on the phase change).

Wait...

Wait wait wait, let me get this straight. We put a man on the moon, developed flying machines composed of several hundred tons of steel, and we just now BARELY explain why Ice Cubes melt in our drink? You know, sometimes humanity really is....scary. What'll be truly frightning is if scientists come out with an explanation as to why Ice Cube still gets movie roles.

Re:Wait...

One of my college professors in materials science, that retired from Bell Labs to teach, used to say, "I'm pretty sure this is how it works, but I'm not positive. If anyone tells you he is positive, he's either lying, or not smart enough to check that the underlying facts are actually suppositions."

He once told us that he didn't really know how resistors worked, but he did know that if he manufactured them using certain materials in a certain process, he could get resistors that were a certain number of ohms. Today resistors are manfactured all over the world pretty much the same way, but the methods were derived from trial and error, and not some deeper understanding and equations for making the best resistor.

Ever wonder why ice melts?

a. Summary is plagiarized from the article, unless I've missed some nested quotes.
b. These guys took this problem because "the earliest phase of melting has never been seen" but they didn't do that either! All they did was make "see-through crystals that are like small beads and are visible in an optical microscope." Doesn't sound like a hell of a lot of progress to me; anyone care to elaborate?
c. Their main result seems to be that the melting process starts at crystal defects and spreads to create liquidy regions within the crystal. Again, can anyone explain why the melting might not start at defects - the weak points?
I'm sure there's something neater here than I'm seeing; it would be nice if the article had more info.

Killer Instinct is Robert Roy Britt?

From the article submission:

Until now, scientists could not explain why ice cubes in your drink melt. They've known the basics, but the details remained elusive. A breakthrough new study, announced yesterday, supports a leading theory that melting starts when the fundamental structure of matter begins to crack. Melting is considered a basic phenomenon in physics. An understanding of how it works is crucial to gaining a firm grasp on the physical world.

And from the actual article itself:

Until now, scientists could not explain why ice cubes in your drink melt. They've known the basics, but the details remained elusive.

A breakthrough new study, announced today, supports a leading theory that melting starts when the fundamental structure of matter begins to crack.

Melting is considered a basic phenomenon in physics. An understanding of how it works is crucial to gaining a firm grasp on the physical world.

Those look pretty similar to me! Given that the article submission is word-for-word exactly from the article itself, it's fair to assume that the submitter, Killer Instinct, is the same person as the author of the article, Robert Roy Britt. How else could the same text be attributed to two supposedly different people?

If you're going to submit an article, summarize it in your own words. If you're just going to paste in the first few sentences of the article, attribute them to the proper author by using a phrase such as, "Quoted from the article: 'insert quote here'." Removing line breaks is not enough to satisfy the "summarize in your own words" criteria.

Here's an example of what the submission should've looked like if Slashdot cared at all about given proper attribution for written text:

Killer Instinct writes "Ever wonder how ice melts? From the article: 'Until now, scientists could not explain why ice cubes in your drink melt. They've known the basics, but the details remained elusive. A breakthrough new study, announced yesterday, supports a leading theory that melting starts when the fundamental structure of matter begins to crack. Melting is considered a basic phenomenon in physics. An understanding of how it works is crucial to gaining a firm grasp on the physical world.'"

Re:Killer Instinct is Robert Roy Britt?

Gosh, I'd thought it was the editor's responsibility to check legitimacy and attribution were correct.

I am sure that Frosty the Snowman...

Is thrilled to know exactly how he will die come spring.

How, not why

Until now, scientists could not explain why ice cubes in your drink melt.

Scientists does not explain why things happen. Only how.

Corollary

If "pre-melting" truly begins at the defect sites, it would be interesting to see whether ultra-low defect containing crystals melt at a higher temperature. Say, purify and grow a chunk of ice through the same procedure used to fabricate semiconductor grade silicon (Czochalski style or epitaxially), and then see if it holds together through warmer temps.

Re:freezing water

It depends on the fluid's temperature....

Source [straightdope.com]

Dear Cecil:

I have a friend who insists that filling an ice cube tray with warm water will cause the cubes to form more quickly than they would if you started with cold water. He said it had something to do with the air circulation around the trays being affected by the temperature.

Not knowing much about frigidity myself, but being contrary, not to mention skeptical, by nature, I expressed doubt. Cecil, was I right, or is there indeed some basis in fact for this foolishness? --Mary M.Q.C., Santa Barbarba, California

Cecil replies:

You were smart to let me handle this, Mary. God knows what would happen if you tried to experiment with ice cubes on your own.

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 ARISES

Dear 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., Chicago

Dear 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

Re:freezing water

It is called the Mpemba Effect.

More on this phenomenon (history en possible explanations) here [ucr.edu]

Re:freezing water

This is a particularly pervasive myth. Of course, the folklore is incorrect: according to basic thermodynamics, a quantity of warm water will invariably take longer to freeze than an equal quantity of cold water.

Note that key phrase, "an equal quantity" -- in an experiment with two uncovered containers of hot and cold water, you'll find that the resultant mass of water in each of the containers is anything but: a good deal of water from the hot water container is lost to evaporation. So, with a decreased mass, it's easy for the originally hot water to cool more quickly than a significantly larger mass of cold water.

Essentially, hot water does cool faster than cold water in an uncovered container, but you end up with significantly less ice than if it were originally cold.

Dancing water

This reminds me of a similar effect that I often observe while cooking, particularly while stir-frying (or any other high-heat method). That is: a drop of water will evaporate more quickly in a pan on medium heat that it will in a pan on high heat.

The reason? When a drop of water hits a pan on very high heat, the underside is instantly tranformed into a layer of vapor which then acts as a buffer between the pan and the liquid on top. So insulated, the water droplet will then "dance" and roll around the pan like a ball bearing. The drop can remain in the pan for a surprising amount of time, though I have never personally measured.

Re:freezing water

using hot water makes it faster than using cold water, right?

Water that's really hot will loose heat more rapidly than cool water in the same surroundings. What people don't get is that once the hot water has cooled off, it now cools at the slower rate.

What actually IS useful about freezing hot water is that there are a lot less air bubbles so the ice doesn't crack and throw shards out when you pour freshly brewed tea over it on a hot summer afternoon.