|04-04-2007, 12:14 PM||#1|
Join Date: Apr 2001
Hot ice and other water mysteries
Scientists Make Ice Hotter Than Boiling Water
Scientists have turned water into ice in nanoseconds, which means really, really fast. That's not the most interesting part, though. The ice is hotter than boiling water.
The experiment was done at the Sandia National Laboratories' huge Z machine, which generates temperatures hotter than the sun (setting a record here on Earth) and where researchers test what we know about those plain vanilla "phases" in textbooks: solid, liquid and gas.
"The three phases of water as we know them—cold ice, room temperature liquid, and hot vapor—are actually only a small part of water’s repertory of states," said Sandia researcher Daniel Dolan. "Compressing water customarily heats it. But under extreme compression, it is easier for dense water to enter its solid phase [ice] than maintain the more energetic liquid phase [water]."
Ice is odd. Most things shrink when they get cold, and so they take up less space as solids than as liquids. But regular ice, of course, takes up more space than water. A simple experiment of putting a (preferably cheap) full water bottle in the freeze overnight will demonstrate this.
In the new experiment, however, the volume of "water shrank abruptly and discontinuously, consistent with the formation of almost every known form of ice except the ordinary kind," according to a Sandia statement Thursday.
Apparently, there are at least 11 other types of ice that most of us don't know about. They're classified by how they behave at certain temperatures and pressures. You might have heard of one: Supercooled water can be below 32 degrees but not frozen.
Problem is, scientists don't know the specifics of all these states. Hence the Sandia research.
Dolan said the work "helps us understand materials at extreme conditions."
He was surprised by how quickly the water froze. Rapid compression—around 70,000 times normal atmospheric pressure in a tiny fraction of a second—caused the rapid freezing, he figures. When the pressure was relieved, the ice melted.
"Apparently it’s virtually impossible to keep water from freezing at pressures beyond 70,000 atmospheres," Dolan said.
That's good to know, for people who are trying to solve water's many mysteries.
The New Mystery of Water
With researchers decoding DNA and smashing open atoms, you might assume the science of everyday water, life's most basic substance, is well understood. But recent experiments probing how water molecules link together have come up with conflicting results.
Scientists now admit they don't understand the intricacies of how water works.
"The structure of water – the reason for its peculiar properties – is a major question in chemistry and physics," said Richard Saykally from University of California, Berkeley.
Water was thrust into the scientific limelight this past April, when a team of scientists led by Anders Nilsson from the Stanford Linear Accelerator Center presented evidence that water is more loosely bound than previously thought.
The response has not been all that welcoming. "A lot of people have a very strong opinion about water," Nilsson said in a telephone interview.
At a recent conference on water, some of the attendees stayed up all night debating these results. Saykally was one of them. He calls the results from Nilsson’s group a drastic revision of how water is understood.
"If they are right, they’re going to win a Nobel Prize," Saykally told LiveScience.
But he doesn’t think they are right. In the Oct. 29 issue of the journal Science, Saykally and his collaborators published results that contradict the revisionists’ findings.
(cont'd on site)