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Water can remain in a liquid state in temperatures up to -42°C

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A recent study has been attempting to determine the coldest negative temperature that water can remain in a liquid state.  In order to do this, a team of physicists launched tiny droplets of pure water into vacuum chamber.

At what temperature do water droplets freeze?

Water droplets, often found in our atmosphere in negative temperature still in their liquid form, can instantly freeze when in contact with an impurity to form ice.  However it would be interesting to know up to what negative temperature water can remain in a liquid form.  A team of European physic-chemists lead by the Robert Grisenti University of Frankfort carried out a study. They discovered that water can remain in its liquid form up to negative temperature of -42.5°C.  Their research was published in the journal Physical Review Letters in November 2017.

What did the study involve?

Researchers used water droplets the size of 3 microns which they pulverised in a vacuum chamber so that they could observe the evaporation process.   In fact the liquid vapor’s changing state uses energy in the form of heat, which cools the droplets and causes freezing.  This process is called supercooling. Over the course of the droplets’ transformation, the researchers evaluated droplet temperature with an accuracy of 0.2% by observing how the droplets scattered the laser light as they decreased. The droplets’ reduced size helped researchers to understand the degree of evaporation, and as a result could understand more about energy loss and temperature.

The results and their importance

The study indicated the their results meant previous estimations made on larger droplets were called into question.  This research provides valuable information about the hydrogen bonding network in liquid water during the supercooling process. Valeria Molinero, a chemist at the University of Utah (United States), predicted in 2011 with her team that the lowest temperature at which liquid water could be cooled was -48 ° C. Well this professor’s evaluated guess, was almost right, if only to a few degrees!

Sources : Physical Review LettersScience & Vie

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