Advanced #9

Liquid water exists at extremely low temperatures and freezes upon warming

Under certain conditions, water can be liquid at very low temperatures and crystallize upon warming.

Scientific Explanation

That water freezes upon cooling seems self-evident. Yet under certain conditions, the opposite occurs: water remains liquid at extremely low temperatures and crystallizes upon warming. This counterintuitive behavior has been experimentally confirmed and represents one of the most fascinating anomalies of water.

The key lies in amorphous ice. When amorphous (glassy) ice is slowly warmed, it passes through a glass transition and becomes an extremely viscous liquid — at temperatures between approximately minus 140 and minus 120 degrees Celsius. This liquid water exists far below the normal freezing point. Upon further warming, it reaches a temperature where molecular mobility is sufficient to form crystalline ice nuclei — and the water suddenly freezes as the temperature rises.

This behavior has also been observed in nanopores, where spatial confinement prevents crystallization and water remains liquid at temperatures as low as minus 163 degrees Celsius. In such confined geometries, water can exist in states that are inaccessible on the normal phase curve.

The existence of liquid water at such extreme temperatures provides important clues about the structure and behavior of water in the so-called “no man’s land” — the temperature range between approximately minus 38 and minus 120 degrees Celsius, where conventional experiments fail due to immediate crystallization.

Liquid Water at Extremely Low Temperatures Temperature-phase diagram showing how water can exist as a liquid at extremely low temperatures when confined in nanopores or at high pressure, and how it can crystallize upon warming -- the opposite of normal freezing behavior. Temperature Pressure (MPa) -150 °C -100 °C -50 °C 0 °C Crystalline Ice Liquid Water (at extreme conditions) Amorphous Ice Warming causes crystallization! Liquid Water at Extremely Low Temperatures
Liquid water at extremely low temperatures: under certain conditions, water crystallizes upon warming rather than upon cooling.

Everyday Relevance

While this phenomenon may seem exotic, it has significance for several fields. In astrophysics, amorphous ice plays an important role: on comets and in interstellar clouds, water primarily exists in amorphous form. When these ice grains approach the sun and are warmed, the transition from amorphous to crystalline ice may proceed similarly — with implications for the release of trapped gases.

For cryobiology, understanding these low-temperature phases is essential. When recovering cells or biological samples from cryopreservation, the warming process must be carefully controlled to prevent the amorphously preserved water from crystallizing during rewarming and damaging the cells.