[Article] Water is weird. A new type of ice could help us understand why

Ice cubes float in water because they’re less dense than the liquid. But a newfound type of ice has a density nearly equal to what’s in your water glass, researchers report in the Feb. 3 Science. If you could plop this ice in your cup without it melting immediately, it would bob around, neither floating nor sinking.

The new ice is a special type called an amorphous ice. That means the water molecules within it aren’t arranged in a neat pattern, as in normal, crystalline ice. Other types of amorphous ice are already known, but they have densities either lower or higher than water’s density under standard conditions. Some scientists hope this newly made amorphous ice could help solve the scientific mysteries that swirl around water.

To generate the new ice, scientists used a surprisingly simple technique. Called ball milling, it involves shaking a container of ice and stainless steel balls, cooled to 77 kelvins (nearly –200° Celsius). The researchers were motivated by curiosity; they didn’t expect the technique to produce a new amorphous ice. “It was a sort of Friday-afternoon idea we had, to just give it a go and see what happens,” says physical chemist Christoph Salzmann of University College London.

An analysis of how X-rays scattered from the frosty stuff suggested they’d created an amorphous ice. And computer simulations that mimicked the effects of ball milling revealed that a disordered structure could be produced by layers of ice sliding past one another in random directions, in response to the forces exerted by the balls.

“You have to be open, as a scientist, for the unexpected,” says chemical physicist Anders Nilsson of Stockholm University, who was not involved with the research. The ball milling technique, he says, “was quite innovative to do.”


Since the material was made by mashing up normal ice, its relationship to liquid water is unknown. It’s unclear whether it can be produced directly, by cooling liquid water. Not all amorphous ices share this connection with their liquid state.

If the new ice does have this link to the liquid, the ice might help scientists better understand water’s quirks. Water is puzzling because it flouts the norms for liquids. For example, whereas most liquids become denser upon cooling, water gets denser as it gets closer to 4° C, but becomes less dense as it is cooled further.

Source: https://www.sciencenews.org/article/water-ice-amorphous-physics-chemistry