Is the third law of thermodynamics in jeopardy?

Washington, August 8 : Scientists have said that what goes on at a molecular level during the process when water freezes, seems to be in conflict with the third law of thermodynamics.

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.

Then, the molecules should line up in an orderly fashion.

But, 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.

To define exactly what happens when it freezes, 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 examined the crystal lattice structure of ice.

According to Cummings, "The hydrogen atoms stop moving, 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."

This has forced scientists to think whether the Third Law is truly a law, or more of a guideline.

"It's a big fundamental question," said Cumings. "If there's an exception, it's a rule of thumb," he added.

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.

ANI