Researchers in Japan have unveiled a remarkable phenomenon in water behavior, revealing that under certain conditions, water molecules can exist in both solid and liquid states simultaneously. This discovery challenges traditional perceptions of water and opens new avenues for scientific exploration.
This intriguing state, termed the premelting state, occurs when water is confined to exceptionally narrow spaces. In conventional conditions, ice and liquid water exhibit distinct behaviors: ice has molecules locked in rigid formations, while liquid water allows molecules to move freely. However, in this new state, as described in a recent study, water molecules maintain a fixed position akin to ice while also exhibiting rapid spinning movements typical of liquids.
Makoto Tadokoro, a chemist from the Tokyo University of Science, explains, “The premelting state involves the melting of incompletely hydrogen-bonded H₂O before the completely frozen ice structure starts melting during the heating process. It essentially constitutes a novel phase of water in which frozen H₂O layers and slowly moving H₂O coexist.”
To observe this unusual behavior, the research team utilized a complex experimental setup. They worked with a variant of water known as heavy water, where the hydrogen atoms are replaced with deuterium, an isotope that contains a neutron in its nucleus. This heavy water, or D₂O, was confined within rod-shaped crystals featuring tiny hydrophilic channels measuring just 1.6 nanometers wide. After freezing the heavy water in these channels, the researchers gradually warmed it and monitored the changes using static solid-state deuterium nuclear magnetic resonance (NMR) spectroscopy.
The results revealed a hierarchical, three-layered structure within the water, characterized by varying types of molecular movements and interactions in each layer. This unique arrangement is likely most familiar to many as a thin film of water that forms on ice surfaces, even when temperatures remain below freezing. However, the behavior of water in this state differs significantly from that of bulk ice.
The study contributes to a growing body of knowledge regarding the unusual properties of water at the nanoscale. Water is already known to display peculiar behavior when confined, such as changes in electrical properties, the ability to remain “unfreezable” at temperatures approaching absolute zero, and the capacity to freeze solid under conditions that would typically cause it to boil.
The implications of this research extend beyond academic curiosity. Tapping into the quirks of water’s behavior could lead to practical applications. Tadokoro suggests that creating new ice network structures may enable the storage of energetic gases like hydrogen and methane, as well as the development of water-based materials such as artificial gas hydrates.
This groundbreaking research was published in the Journal of the American Chemical Society in January 2024, marking a significant step forward in the understanding of water’s complex behavior and potential applications in various scientific fields.
