Supercooled Water Transforms into New Liquid at Extreme Temperatures

When water becomes cold, it turns into ice. The evidence can be found all around us in the forms of massive glaciers, ice skating rinks or in our own freezers in ice cube trays. Yet it turns out that water enters another state when it becomes supercooled. Scientists have discovered that water transforms into a new form of liquid at extreme temperatures.

In order to examine the physical properties of water that's cooled to extreme temperatures, researchers employed a simulation model called Water potential from Adaptive Force Matching for Ice and Liquid (WAIL). This allowed the scientists to test exactly how water reacted at extremely cold temperatures. It turns out that while normal water is a high-density liquid, a low-density liquid emerged at lower temperatures.

"On a microsecond time scale, the water did not actually form ice but it transformed into a new form of liquid," said Feng "Seymour" Wang in a news release. "The study provides strong supporting evidence of the liquid-liquid phase transition and predicted a temperature of minimum density if water can be cooled well below its normal freezing temperature. Our study shows water will expand at a very low temperature even without forming ice."

So how cold does this water need to be? Researchers found that this "liquid-liquid" phase occurred at 207 Kelvins, or 87 degrees below zero. At that point, the water became a much lower density liquid, which has important implications for understanding the properties of water.

In fact, the recent findings are crucial for learning more about the basic processes during cryoprotection, which is the preservation of tissue or cells by liquid nitrogen so that they can be thawed without damage. In addition, the research could be used to explain the many anomalous behaviors of water. This, in turn, could aid in future studies that deal with supercooled water or extremely low temperatures.

The findings are published in the Proceedings of the National Academy of Sciences.