Meta-materials Mimic Ice And Illuminate Why Water-ice Doesn’t Fully Conform To Third Law Of Thermodynamics

By | August 12, 2008

Meta-materials Mimic Ice And Illuminate Why Water-ice Doesnt Fully Conform To Third Law Of Thermodynamics

“Ye canna change the laws of physics!” Scotty warned Captain Kirk on “Star Trek.” But engineers and physicists at the University of Maryland may rewrite one of them.

The Third Law of Thermodynamics is on the minds of John Cumings, assistant professor of materials science and engineering at the University of Maryland’s A. James Clark School of Engineering, and his research group as they examine the crystal lattice structure of ice and seek to define exactly what happens when it freezes.

The Third Law of Thermodynamics states that as the temperature of a pure substance moves toward absolute zero (the mathematically lowest temperature possible) its entropy, or the disorderly behavior of its molecules, also approaches zero. The molecules should line up in an orderly fashion.

Ice seems to be the exception to that rule. While the oxygen atoms in ice freeze into an ordered crystalline structure, its hydrogen atoms do not.

“The hydrogen atoms stop moving,” Cumings explains, “but they just stop where they happen to lie, in different configurations throughout the crystal with no correlation between them, and no single one lowers the energy enough to take over and reduce the entropy to zero.”

So is the Third Law truly a law, or more of a guideline? … Materials that violated the Third Law as originally written were found in the 1930s, mainly non-crystalline substances such as glasses and polymers. The Third Law was rewritten to say that all pure crystalline materials’ entropy moves toward zero as their temperatures move toward absolute zero. Ice is crystalline—but it seems only its oxygen atoms obey the Law. Over extremely long periods of time and at extremely low temperatures, however, ice may fully order itself, but this is something scientists have yet to prove. … continued on science daily

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