The Two Faces of Water
Water has some extraordinary properties. Can they be better explained by considering it as a mixture of two different liquids?
Water is as omnipresent as it is unusual. It differs drastically from most other liquids in a number of properties, such as surface tension, heat capacity, compressibility, and melting and boiling points. Some scientists explain the strange behavior by considering water not as a complicated substance, but rather as a mixture of two simple substances with a complicated relationship. Other experts vehemently disagree: Such a statement does not fit the basic principles of physical chemistry.
Over the past decade, emotions have run high in the academic dispute. Renowned water researcher Anders Nilsson of Stockholm University says the question "reveals very strong, almost religious views". Scientists generally attribute the strange properties of water to bonding through something called hydrogen bonds. However, what exactly is happening is a matter of debate, particularly when the water is in a supercooled state. Then it should actually freeze, but it doesn't happen.
Like many chemists, Nilsson thought at the beginning of his career that the structure of water should be well understood. Then he realized that wasn't the case. For many years he has devoted himself entirely to the peculiarities of the substance. His more recent work lends weight to a hypothesis that is disputed among experts: in water, two different liquid structures exist separately from each other.…
