Researchers claim that ice cubes are less dense than liquids in water. But a newfound type of ice has a density nearly equal to that found in your water glass on February 3 Science.
The new ice is a special kind of amorphous ice. That means the water molecules inside it aren't organized in a neat sequence, as in normal, crystalline ice. Other types of amorphous ice are known, but they have density values either lower or higher than water's density under standard conditions.
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Scientists used a relatively simple technique: ball milling, which involves shaking a container of ice and stainless steel balls at 77°C (nearly –200°C). "It was a Friday-afternoon idea we had, to just try it and see what happens." says physical chemist Christoph Salzmann of University College London.
As a result of the effects of the balls, computer simulations that mimicked the effects of ball milling revealed that layers of ice might form a disordered structure.
"You have to be open, as a scientist, to the unexpected," says Stockholm University chemical physicist Anders Nilsson, who was not involved in the study. The ball milling technique, he says, "was quite novel to achieve."
The relationship between normal ice and liquid water is unclear since it was formed by smashing up regular ice. It's unclear whether it may be produced directly, by cooling liquid water. Not all amorphous ices have this connection with their liquid state.
If the new ice does have a connection to the liquid, it might help scientists better understand water's peculiarities. Water is puzzling because it contravenes the accepted wisdom of liquids. For example, water becomes less dense as it cools further.
Many scientists believe water's weirdness is related to its ability to remain a supercooled liquid (SN: 9/28/20); under such circumstances, water is thought to exist in two different phases, a high-density liquid and a low-density liquid, and that dual nature might explain water's behavior in more typical conditions (SN: 11/19/20).
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Salzmann and colleagues argue that the new ice could be a special kind of water, called a glass. Glasses can be created by cooling a liquid fast enough to keep the molecules from changing into a crystal structure. Other substances can also be used to make glasses.
Scientists would need to understand how the new ice behaves in that dual-liquid state. And this might aid scientists in identifying what's really going on in difficult-to-study supercooled conditions.
Some researchers are unsure if the new material will have a direct connection to the strange physics of liquid water. Thomas Loerting of the University of Innsbruck in Austria believes that the ice is "closely related to very small, distorted ice crystals," rather than the liquid form of water.
According to computational physicist Nicolas Giovambattista of Brooklyn College of the City University of New York, earlier computer simulations suggested that water might form glasses of a wide range of densities comparable to liquid water. "It opens doors for fresh questions."