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How Ice Melts
Posted by
Zonk
on Fri Jul 01, 2005 11:49 PM
from the i-can-sleep-tonight dept.
from the i-can-sleep-tonight dept.
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."
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High-Tech Electro-Defroster 109 comments
DahBaker writes to mention a News.com story about an ingenious way to de-ice a surface. From the article: "Dartmouth College engineering professor Victor Petrenko, not to be confused with one of the Champions on Ice, has devised a way to use a burst of electricity to remove ice caked on walls or windows. For surfaces coated with a special film, the jolt gets rid of ice in less than a second, far less time than it takes to hack at it with an ice scraper. While drivers might find easy-cleaning windshields convenient, the technology--called thin-film pulse electrothermal de-icing, or PETD--could have significant economic impact if widely deployed. It could, for example, cut the costs of repairing power lines downed by ice storms and keep plane windshields frost-free, decreasing fuel consumption."
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Hmmmmm... (Score:4, Funny)
No.
Re:Hmmmmm... (Score:5, Funny)
Parent
Re:Hmmmmm... (Score:5, Informative)
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.
Parent
Re:Hmmmmm... (Score:5, Insightful)
Parent
Re:Hmmmmm... (Score:5, Funny)
Parent
Anti-Cold (Score:5, Funny)
Re:Anti-Cold (Score:5, Insightful)
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.
Parent
Re:Anti-Cold (Score:5, Informative)
Parent
Re:Anti-Cold (Score:3, Insightful)
There is a difference between knowing ice melts and knowing why or how. The Greek also knew that every day Apollo would ride his sun-chariot. No need to investigate how he did this exactly.
As the parent said: nerds want to know how stuff works.
Not Insightful or Interesting (Score:3, Informative)
But if people really didn't know that the Celsius scale was defined with 0 as the freezing point of water and 100 as the boiling point; well glad I could be useful. There is no mysterious alien mathematical connection, us humans defined the "connection".
Re:Not Insightful or Interesting (Score:4, Informative)
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].
Parent
Re:Anti-Cold (Score:5, Funny)
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.
Parent
Re:Anti-Cold (Score:3, Funny)
What else don't we know? (Score:2, Funny)
Re:What else don't we know? (Score:3, Interesting)
It's about time... (Score:4, Funny)
Ever wonder..? (Score:2)
I think matter is ON crack...\
Re:Ever wonder..? (Score:3, Insightful)
Venus' orbital eccentricity: 0.00677323
Neptune's 0.00858587
Earth's: 0.01671022
Venus' surface temperature ranges from about 820 degrees to nearly 900 degrees F
Earth's surface temperature ranges from about -80 degrees to around 130 degrees F
Neptune's mean cloud temperature ranges from -315 to -307 degrees F (Temperature varies vastly by cloud elevation, but probably little across
Not suprising (Score:4, Interesting)
super cooled liquids (Score:3, Interesting)
I have a small fridge here (absocold) it is kind of like the small fridges students use in dorm rooms.
If I put a bottle of water in the freezer compartment
most of the time it will not freeze.
what is fun is to hand it to someone and ask them to shake it or even let me them drink the water.
I will suddenly turn to slush. It is very strange to have water freeze in you mouth.
Wait... (Score:5, Funny)
Re:Wait... (Score:4, Insightful)
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.
Parent
Ever wonder why ice melts? (Score:4, Interesting)
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.
The awesome power of Pykrete! (Score:3, Interesting)
Supposedly tissue paper works as well as sawdust. So you can tell all your friends you know how to beat someone to death with a wet paper towel.
--grendel drago
Re:The awesome power of Pykrete! (Score:3, Insightful)
Great... (Score:3, Funny)
Killer Instinct is Robert Roy Britt? (Score:5, Insightful)
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:
Re:Killer Instinct is Robert Roy Britt? (Score:4, Insightful)
Parent
Re:Killer Instinct is Robert Roy Britt? (Score:3, Insightful)
That pratice hides what people think, their individuality, their self. It is no better then a news agregator. What make's slashdot different from a machine is the people, but for better "scores" people sundenly start acting as machines. If on
Ah, as usual.... (Score:3, Insightful)
...smartass slashdotters crack jokes about a new discovery to hide their own insecurities. I, for one, freely admit I have no idea how ice melts.
1+1=2 anyone?
Accuracy ? (Score:3, Interesting)
"So Yodh's team made some big atoms. Specifically, they made see-through crystals that are like small beads and are visible in an optical microscope."
By "see-through crystals" i'm assuming they mean optically transparent crystals constructed from small beads, not crystals that are like beads that then form a larger crystal structure, although from the wording, it's impossible to tell.
"The spheres swell or collapse significantly with small changes in temperature, and they exhibit other useful properties that allow them to behave like enormous versions of atoms for the purpose of our experiment,"
As far as I know.. atoms dont significantly change size when temperature changes.... they change how fast they move. I dont really see how size-changing beads model water molecules here, unless it's on a macroscale where a molecules are considered to expand as a group with increased temperature... but that sort of would defeat the pupose of the whole study...
On the other hand.... I think that the research is probably solid, espcially if it's being published in Science, a extremely selective journal. I think the article just fails to explain it well, and takes quotes out of context. Sadly, this is all too common in scientific journalism.
Bad reporting? (Score:3, Insightful)
It's true that the *exact* mechanism for melting has not been "seen", but the concepts really are well known. Our models are good enough that computer simulations can be very accurate. I have seen several which show features such as surface melting, for instance.
Also, it is absolutely expected that melting begin at defects, but this does not mean that "melting begins below the melting point" as the article suggests. These areas are locally amorphous and there is no reason that they should begin melting at the crystal's melting point. Really, it's all in the free energy equations.
I'm guessing that the real result has been butchered by the article.
I am sure that Frosty the Snowman... (Score:5, Funny)
So How Does Water Freeze? (Score:3, Informative)
How, not why (Score:5, Insightful)
Until now, scientists could not explain why ice cubes in your drink melt.
Scientists does not explain why things happen. Only how.
Abstract (Score:3, Informative)
Corollary (Score:4, Interesting)
Re:freezing water (Score:5, Informative)
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
Parent
Re:freezing water (Score:5, Informative)
More on this phenomenon (history en possible explanations) here [ucr.edu]
Parent
Re:freezing water (Score:5, Informative)
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.
Parent
Re:freezing water (Score:3, Informative)
IIRC, the explanation for the ice-cube-trays-in the-freezer 'anomaly' seems to involve the specific temperatures of the two samples, the insulating sides of th
Dancing water (Score:5, Interesting)
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.
Parent
Re:Dancing water (Score:3, Informative)
Re:freezing water (Score:3, Interesting)
I hate to nitpick, but thermodynamics will not tell you that. The heat transfer details depend on the nature of the system, which is outside the scope of thermodynamics.
You could imagine two closed cylindrical containers, each initially filled with a substance in a liquid state. The liquid o
Re:freezing water (Score:4, Interesting)
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.
Parent
Ice Spikes (Score:3, Interesting)
In case you didn't get it... (Score:3, Insightful)
http://www.nuklearpower.com/daily.php?date=041028 [nuklearpower.com]
Here's how it works:
http://www.nuklearpower.com/daily.php?date=041125 [nuklearpower.com]
And seen in action:
http://www.nuklearpower.com/daily.php?date=041102 [nuklearpower.com]
Re:In case you didn't get it... (Score:3, Informative)
You mean Kurt Vonnegut [wikipedia.org]. Strange error to make in a correction :-)
Re:Boiling Point, Stupid! (Score:3, Informative)
This is the entire methodo
Re:Boiling Point, Stupid! (Score:3, Informative)
You are right in the broad overview, but wrong on the details. The boiling temperature of a mixture is not necessarily due to the boiling temperatures of its two components. The boiling temperature of a solution is not a linear combination of t