Water is a very strange thing. In our everyday experience, when liquid water falls below 0 ° C (32 ° F or 273.15 Kelvin), it becomes OK, freezes in solid form. But the snow, it turned out, is also rather strange.
Most of the time, the ice seems to be the same stable solid, no matter where you look. Scientists know differently.
Depending on how liquid water is handled, its transformation into ice, called crystallization, can play a variety of different roles, and in some cases, it can take temperatures above 0 સે C before this transition occurs. .
This is the realm of supercooling – scientific experiments that reduce the temperature of liquid water as far as the normal freezing point, even though it still retains its liquid form. There are various ways to do this – with selective applications of temperature and pressure – to create a myriad of exotic ice that has been found to exist.
In a new study, however, scientists wanted to examine water at extremely cold temperatures before it crystallized, while it was still in its liquid state.
The surprising thing they found was that, under the right circumstances, supercooled water could actually be two liquids in one.
U.S. “We’ve shown that liquid water is not only relatively stable at extremely cold temperatures, it’s in two structural perspectives,” says Greg Kimmal, a chemist at the Department of Energy’s Pacific Northwest National Laboratory (PNNL).
“The findings illustrate the long-running controversy over whether deeply deep supercooled water always crystallizes before it is balanced. The answer is no.”
During laboratory experiments, Kimmel’s team operated a laser on a thin film of ice, creating a momentary eruption of melted, super-cooled water at very cold temperatures – like the state of Arendal in the midst of a royal crisis before it quickly stabilized again. .
In this ultra-short window, each surviving only nanoseconds, the researchers observed liquid water present in two different states – a form of sitting high density with a low density structure.
The authors write in their paper, “Water is mild from its initial configuration to a steady state configuration before the start of crystallization for an experimentally accessible temperature range.”
“These results support the hypothesis that supercooled water at low pressure can be described as a mixture of two, structurally different components, ranging from 135 to 245 k. [–138.15 °C/–216.67 °F to –28.15 °C/–18.67 °F]”
This is not the first time such duality has been found in water. Previous experiments by other scientists have also revealed a mixture of structures in the liquid state of water – but this is the first time such a hybrid has been found at such a low temperature.
The reason why liquid water can be absolutely super-cooled – as opposed to ice cubes in your freezer – is that in special circumstances (including the absence of dust or other small particles), it is possible to deprive small seed liquid water needed to help kickstart. The process of crystallization.
In nature, liquid water in the atmosphere can survive in its liquid state, as long as it does not collide with such seeds. A single snowflake is what takes to trigger metamorphosis.
“Liquid water cools in the upper atmosphere,” says Bruce K, a chemical physicist at PNNL.
“It freezes quickly when it encounters snowflakes, and then falls to Earth in the right position. There’s really only one time when most people will experience the effects of supercooled water.”
Until such time, however, liquid water, cooled south of its conventional freezing point, will retain its liquid properties as long as it is deprived of snowflakes or similar crystallization triggers.
Experimentally, we now know what a different liquid water looks like when it cools enough in such circumstances.
For the ephemeral instant, it is composed of a combination of these -density densities and low-density formats, in which the temperature seems to decrease with a -density ratio in the mixture, the temperature being 245K.
In other words, for nanoseconds or two, at least, water seems to be two liquids at once.
“When it’s cold, you probably have 1,000,000ths of a second of it before you freeze,” Kimmel said.
“But for the water molecules dancing around, it’s too long for them to say, ‘I’ve got the structure I want. I won’t change.’
These findings are reported Science.
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