The water is weird. A new type of ice could help us understand why

Ice cubes float in water because it is less dense than liquid. But the newly discovered type of ice has a density It is almost equal to what is in your glass of waterResearchers report on February 3 Sciences. If you can get that ice into your cup without it melting instantly, it will just swirl around, not float or sink.

New ice is a special type called amorphous ice. This means that the water molecules inside are not arranged in a neat pattern, as they are in regular crystal ice. Other types of amorphous ice are already known, but their density is either lower or higher than that of water under standard conditions. Some scientists hope this newly created amorphous ice will help solve scientific mysteries surrounding water.

To generate the new ice, the scientists used a surprisingly simple technique. Called ball milling, it involves shaking a bowl of ice and stainless steel balls, cooled to 77 °C (nearly 200 °C). The researchers were motivated by curiosity. They did not expect the technology to produce new, amorphous ice. “It was kind of an idea we had on Friday afternoon, to try it out and see what happens,” says physical chemist Christoph Salzmann of University College London.

An analysis of how X-rays scatter from the frozen material indicated that it created amorphous ice. Computer simulations simulating the effects of ball grinding revealed that a disordered structure can be produced by layers of ice sliding over one another in random directions, in response to the forces exerted by the balls.

“You have to be open, as a scientist, to the unexpected,” says chemical physicist Anders Nilsson of Stockholm University, who was not involved in the research. He says the ball milling technology “was completely innovative.”

Left: schematic diagram of normal ice.  Right: Computer simulation result showing the result of ice being vibrated with steel balls, showing a chaotic mixture
Computer simulations revealed how an ordinary crystalline ice structure (left) can transform into a disordered solid when the ice is shaken with stainless steel balls at a low temperature. When the ice layers were randomly displaced in the simulation, the water molecules (red and gray) rearranged into a jumbled mixture called amorphous ice (right).Cambridge University

Since the substance is made by mashing natural snow, its relationship to liquid water is unknown. It is unclear whether it can be produced directly by cooling liquid water. Not all amorphous ice shares this association with its liquid state.

If the new ice has this connection to the liquid, the ice may help scientists better understand the quirks of water. Water is baffling because it violates the fluid standards. For example, while most liquids become denser when cooled, water becomes denser the closer it gets to 4°C, but becomes less dense the further it is cooled.

Many scientists suspect that the water’s oddity is related to its behavior as a Super cold liquid (S.N.: 9/28/20). Pure water can remain a liquid at temperatures below the freezing point. Under these conditions, it is liquid water It is believed to exist in two different phasesa high-density liquid and a low-density one, and this dual nature can explain the behavior of water under more typical conditions (SN: 11/19/20). But there is still a lot of uncertainty about this idea.

Salzmann and his colleagues suggest that the new ice could be a special form of water called glass. Glasses can be made by cooling a liquid fast enough that the molecules can’t rearrange into a crystal structure. Glass in window glass is an example of this type of material, made by cooling molten silica sand, but other materials can also form glass.

If the new ice is a glassy state of water, scientists will need to figure out how it fits into that two-liquid picture. This could help scientists discover what really happens in supercooling conditions that are difficult to study.

But some researchers are skeptical that the new material has any connection to the strange physics of liquid water. Physical chemist Thomas Leuerting of the University of Innsbruck in Austria believes that ice is “closely associated with very small, deformed ice crystals,” rather than the liquid form of water.

However, previous computer simulations suggested that water could form cups with densities close to liquid water, says computational physicist Nicholas Giovambattista of the City University of New York’s Brooklyn College. These simulations produced structures similar to those seen in computer simulations of ball ice grinding, says Giovambattista, who was not involved in the new research. “It opens doors to new questions. It is new, so what is it?”

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