(ORDO NEWS) — When water gets very cold, molecules can cluster into larger structures while still remaining liquid.
They can do this in two ways, which results in the separation of liquids with different densities. A new study has shed light on the shapes of these supermolecules.
The idea of two liquid phases for water well below freezing was proposed over 30 years ago, but could not be proven at the time.
Two years ago, modeling of this process confirmed this hypothesis. An article on the relevant topic was published in the journal Nature Physics.
Scientists have noticed that supercooled water can form liquid phases with high and low densities. They are different from heavy water, which is formed when deuterium atoms replace some of the normal hydrogen in water.
The composition of water is the same, and the density depends on how the molecules arrange themselves.
According to the article, in supercooled, high-density water, molecules can entangle like a pretzel (technically a shamrock knot) or bound rings favored by amateur magicians (Hopf’s link).
“The system is able to simultaneously minimize its volume and maximize the number of links in the network, forming nodes and links,” the document notes.
Meanwhile, as previously suggested, the low-density liquid phase includes unentangled rings of water molecules, and the space in the middle contributes to how light this phase can be.
“This discovery has given us a whole new perspective on what is now a 30-year-old research problem, and hopefully this will only be the beginning,” said University of Birmingham PhD student Andreasa Neophytou.
Unfortunately, we are still far from observing water molecules in a real experiment, so the results are still coming from a computer model.
To make the calculations manageable, the authors used the fact that, at these temperatures, water self-organizes into colloids, particles made up of thousands of water molecules.
The slower movement of these colloids makes them easier to model than individual molecules, which even at sub-zero temperatures move so fast that they are difficult to track.
“This colloidal water model serves as a magnifying glass for molecular water and allows us to unravel the secrets of water regarding the history of the two liquids,” said Dwaipayan Chakrabarty of the University of Birmingham.
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