Slashdot Mirror
Israeli Scientists Freeze Water By Warming It
ccktech writes "As reported by NPR and Chemistry world, the journal Science has a paper by David Ehre, Etay Lavert, Meir Lahav, and Igor Lubomirsky [note: abstract online; payment required to read the full paper] of Israel's Weizmann Institute, who have figured out a way to freeze pure water by warming it up. The trick is that pure water has different freezing points depending on the electrical charge of the surface it resides on. They found out that a negatively charged surface causes water to freeze at a lower temperature than a positively charged surface. By putting water on the pyroelectric material Lithium Tantalate, which has a negative charge when cooler but a positive change when warmer; water would remain a liquid down to -17 degrees C., and then freeze when the substrate and water were warmed up and the charge changed to positive, where water freezes at -7 degrees C."
It's not quite Hell, but it's an impressive step in that direction...
I thought pure water doesn't go solid, not until an impurity starts crystal formation that turns the water into a solid?
Salt and anti-freeze just have typical freezing-point depression; there's no way to use them to produce a situation where water that is a stable liquid at one temperature will turn solid if you increase the temperature. The situation in this experiment is that water that's liquid at -17 C will freeze as you head it up towards -7 C.
10 PRINT CHR$(205.5+RND(1)); : GOTO 10
I don't remember the science story yesterday Physicists Discover How To Teleport Energy being called Japanese Physicists Discover How To Teleport Energy. Is the fact these scientists are Israeli title worthy?
One of these guys managed to turn water into wine 2000 years ago...
You clearly must be an American, since you compare beer to water. Over here in the old world, we know there is a difference by the taste for one.
MMO Quests are like orgasms:
You may solo them, I prefer them in a group.
I thought pure water doesn't go solid, not until an impurity starts crystal formation that turns the water into a solid?
In many cases, the surface of the container has defects which can play that role.
Gravitation is a theory, not a fact.
A pyroelectric lithium tantalate ice cube tray? In animal shapes?
You are welcome on my lawn.
I thought pure water doesn't go solid, not until an impurity starts crystal formation that turns the water into a solid?
This comment seems really unintuitive so I looked around a little. Ice can actually form entirely without crystallization, by cooling it to ~137 C in a matter of milliseconds. The article also mentions that "pure water, in the absence of any nucleating surface, can remain in a supercooled liquid state down to temperatures as low as -40C". I guess that means that pure water will begin crystallizing at this temperature anyway.
Exactly, this is well known, and is the difference between homogeneous nucleation caused by the massive undercooling providing the energy to nucleate ice spontaneously versus heterogeneous nucleation which requires much less free energy and occurs dependent on surfaces.
It is not scientifically interesting that they warmed it to get it to freeze, that's just a comparison of freezing points... it's interesting that the charge of the surface modified the freezing/nucleation point. Frankly, I am amazed that this was published in Science; it seems like worthwhile research, but for a journal more like, say... applied physics letters or a more specific interest journal. Kudos to the researchers for managing to spin it as a general-interest paper when it is in fact a fairly simple observation of an obscure phenomena.