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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."
No.
A guy walks into a bar... well, I forgot the joke, but the punchline is that he's an alcoholic.
I can finally sleep at night!
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.
From the article submission:
And from the actual article itself: 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:
Source
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
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.
Is thrilled to know exactly how he will die come spring.
If you could reason with religious people, there would be no religious people
Until now, scientists could not explain why ice cubes in your drink melt.
Scientists does not explain why things happen. Only how.
thomasdamgaard.dk.
It is called the Mpemba Effect.
More on this phenomenon (history en possible explanations) here
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.
There they were, sitting in the van with all those dials, and the cat was dead. -V. Marchetti, CIA
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.