Water is the most common liquid on Earth, yet it almost defies the laws of thermodynamics. Every known liquid contracts and thickens when cooled. Water does the opposite. As you cool water after it freezes, it shrinks considerably, which is why ice floats easily in ponds, lakes, and oceans.
Now, physicists think they know exactly why. Researchers at the University of Stockholm have provided direct evidence of the importance of long-term exposure to supercooled water. Located at approximately -63 degrees Celsius and 1,000 times normal atmospheric pressure, this extreme boundary marks the point where two different layers of liquid water collide and become one.
This is the second most important element of water known to physicists. The first is sitting in the extreme. If you boil water at about 374 degrees Celsius and compress it under 218 times normal atmospheric pressure, the boundary between the liquid and the gas disappears completely, and an excess liquid is produced.
Although the newly discovered milestone can be reached at extremes, it is subject to instabilities that produce quirks such as water expanding as it cools below 4 degrees Celsius.
A Race Against the Freezing Clock
To find this difficult step, scientists had to put water in extreme conditions of temperature and pressure. In this extreme, sub-zero environment, supercooled water often freezes into solid ice almost instantly. Measuring the liquid before crystallization takes place requires equipment with extraordinary sensitivity.
“We have to do everything very quickly,” chemical physicist Anders Nilsson of Stockholm University said. Science News.
The research team, led by Nilsson, went to the Pohang Accelerator Laboratory in South Korea. To avoid the ice problem, they did not start with liquid water at all. Instead, they placed small samples of amorphous ice – a special type of ice with an unstable molecular structure instead of the usual crystalline structure – in a vacuum chamber.
The researchers fired a powerful, nanosecond burst from an infrared laser to quickly burn and melt the amorphous ice. Microseconds later, before the newly formed liquid could refreeze, they scanned the sample using a short X-ray laser to capture its mass and composition.
“What was unique was that we were able to make X-rays at an unprecedented speed before the ice freezes and see how the liquid-liquid transition disappears and a new critical state appears,” says Nilsson.
The Ripple Effect of a Water ‘Black Hole’
X-ray images have confirmed what physics had long suspected. At pressures below the critical point, supercooled water is forced back and forth between two different fluids: the high pressure part and the low pressure part.
But when the team dialed in the right temperature and pressure point, that limit disappeared. The two liquids are combined into one highly unstable state. Within this region, water has a thermodynamic problem, showing a range of high and low turbulence, moving between states.
This extreme point acts as a structural anchor for the behavior of the fluid elsewhere. Its extreme instability produces external radiation, affecting water across a wide range of standard temperatures and pressures, even at ambient conditions in your coffee cup. This may explain why the daily water seems to ruin so many meetings.
Another interesting finding in the study is that the power of the system decreases when it enters the critical region. The water was so deeply disturbed that its changes in shape almost stopped.
Robin Tyburski, a chemical physics researcher at Stockholm University, says: “It seems that you can’t escape the critical point if you enter it, almost like a black hole.”
Key Point for Physics
For physicists who have spent their lives making computer simulations of the strange behavior of water, seeing concrete evidence of this important fact marks the end of a difficult hunt.
“I find it very exciting that water is the only supernatural liquid in the environment where life exists and we know that there is no life without water,” says Fivos Perakis, assistant professor of Chemical Physics at Stockholm University.
“Researchers who study the physics of water can now solve the model that water has an important point in the supercooled regime. The next step is to find the results of these studies on the importance of water in terms of physical, chemical, biological, geological and climate. The big problem in the next few years, “Nilsson added.
The findings were published in the journal Science.
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