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Scientists Are Still Learning New Things About Water

By LIDA TUNESI

Most students learn in grade school that water freezes at 32 degrees Fahrenheit, or zero degrees Celsius. Later, a student might go on to a chemistry class and learn that the freezing point actually depends on pressure, as well. From there, things only get more complicated.

In a new study, researchers showed that supercooled water can exist as two liquids with different densities.

Professor Nicolas Giovambattista (Brooklyn College, The Graduate Center) was an author on the study, which was published in Science.

“This is a fundamental finding that explains naturally many of the anomalous properties of water at low temperatures,” he told Brooklyn College.

Water, the so-called “universal solvent,” has many unique properties and responds to varying conditions differently than other substances. About 30 years ago, researchers predicted that water could exist in two forms—a high-density liquid and a low-density liquid—when cooled to extremely low temperatures. But since ice starts to form so quickly at these temps, these ideas have been hard to demonstrate.

The researchers used a combination of computer simulations and laboratory experiments to show this so-called “liquid-liquid transition” for the first time. They demonstrated that when you cool water to about 63 degrees below zero Celsius, two liquids of different densities form.

This process of cooling a substance below its freezing point without turning it into a solid is called “supercooling.” It is possible only when there is no “seed crystal” around which the rest of the solid build off and start to take shape.