How many degrees Celsius is normal water

Observe liquid water at minus 150 degrees Celsius

30.06.2017



Science has long been looking for the reason why, of all things, water is the molecule of life. Using sophisticated techniques, researchers at the Institute for Physical Chemistry at the University of Innsbruck are able to observe water in a viscous state at temperatures of around minus 150 degrees Celsius and to investigate its properties. Four years ago, Thomas Lörting's team found indications that strongly supercooled water consists of two forms of different density.

"Our experiment at the time showed that there are two different liquid forms of water, depending on the ambient pressure, one with a low density and one with a high density." This finding is extremely astonishing, it could mean that even normal tap water consists of two liquids. The phenomenon can of course only be investigated under extreme conditions, because the two liquids exist separately from one another at very low temperatures.

Water molecules in motion

Now, Thomas Lörting's team and researchers from Stockholm University at the German large research center DESY in Hamburg have examined severely supercooled water with the help of a highly focused X-ray beam. This is because small-angle X-ray scattering can be used to determine the movement of molecules in a sample. "In this experiment, we wanted to see whether the molecules are bound in place like in solids, or whether they move around in space like in a liquid", explains Thomas Lörting.

The samples of amorphous ice - i.e. non-crystallized ice - produced at the University of Innsbruck were bombarded with X-rays at DESY and the movement of the water molecules was determined as a function of the temperature. It was shown that the movement of the molecules increases sharply from around minus 160 degrees Celsius. "From the analysis of the data, we were able to determine the movement space of a molecule at 50 nano-square meters per second, which is a very large area for a molecule," emphasizes Lörting. Even after the transition from high-density to low-density water at around minus 137 degrees Celsius, the molecules move, but not quite as quickly. This dynamic shows that the two phases are actually fluid. "It is like a dream come true to be able to observe how water changes from a glassy state into a viscous liquid and then almost immediately into another, even more viscous substance of a much lower density," says Katrin Amann-Winkel, former member happily of Thomas Lörting's group in Innsbruck and now researcher at Stockholm University.

New form of chemistry possible

In the future, the Innsbruck scientists want to build an experiment in which they can jump back and forth between the two states at will. "To do this, we have to bring the system into a state of equilibrium, which is only possible under high pressure," says Thomas Lörting. There are already ideas as to how the current measurements can be repeated in a high-pressure chamber. In the next few years, the researchers also want to clarify whether chemistry in highly supercooled water only takes place in slow motion, or whether this low-temperature solvent opens the door to a completely new form of chemistry.

The current work was carried out within the framework of the materials and nanosciences research platform at the University of Innsbruck and was financially supported by the Austrian Research Promotion Fund (FWF), among others.

»Original publication

Source: University of Innsbruck


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