Scientists have discovered a new state of matter for water
An international team of scientists have recently found signs that liquid water might actually come in two different states. The researchers were surprised to find a number of physical properties of water change their behaviour between 50℃ and 60℃. This sign of a potential change to a second liquid state could spark a heated discussion in the scientific community. And, if confirmed, it could have implications for a range of fields, including nanotechnology and biology.
States of matter, also called “phases”, are a key concept in the study of systems made from atoms and molecules. Roughly speaking, a system formed from many molecules can be arranged in a certain number of configurations depending on its total energy. At higher temperatures (and therefore higher energies), the molecules have more possible configurations and so are more disorganised and can move about relatively freely (the gas phase). At lower temperatures, the molecules have a more limited number of configurations and so form a more ordered phase (a liquid). If the temperature goes down further, they arrange themselves in a very specific configuration, producing a solid.
This picture is common for relatively simple molecules such as carbon dioxide or methane, which have three clear, different states (liquid, solid and gas). But for more complex molecules, there is a larger number of possible configurations and this gives rise to more phases. A beautiful illustration of this is the rich behaviour of liquid crystals, which are formed by complex organic molecules and can flow like liquids, but still have a solid-like crystalline structure.
Because the phase of a substance is determined by how its molecules are configured, many physical properties of that substance will change abruptly as it goes from one state to another. In the recent paper, the researchers measured several telltale physical properties of water at temperatures between 0℃ and 100℃ under normal atmospheric conditions (meaning the water was a liquid). Surprisingly, they found a kink in properties such as the water’s surface tension and its refractive index (a measure of how light travels through it) at around 50℃.