Can you compress water

Chemistry: More and more bizarre peculiarities discovered in water

Water is inconspicuous. Its molecules are made up of two hydrogen atoms and one oxygen atom, H 2 O in the language of chemistry. Such unadorned connections are mass-produced there. And our senses say the same thing: water is tasteless and odorless, transparent and can be found almost everywhere. Still, water is utterly unusual. The eccentric behaves differently than comparable substances, and researchers reveal new bizarre peculiarities almost every week.

This week, researchers report on a new form of water that was found in contact with a water-repellent surface made of graphite. Molecules lie in liquid form between layers of ice - water that is not liquid or solid, but both. This variant only melts completely at plus 37 degrees, report Noah Kastelowitz and Valeria Molinero from the University of Utah in the "Journal of Chemical Physics".

The most famous quirk is the density anomaly. Virtually all fabrics increase in density when they cool down. The molecules move together, the substance loses its volume. Water is different: its density increases by up to plus four degrees as it cools, but below that it expands again. Why forgotten beer bottles in the freezer make a mess. And why ice floats on top of lakes and why the fish survive in the liquid water below.

Or its heat capacity. It is the highest of all liquids. Water can store a huge amount of solar energy. It heats up, but only slightly. That is why the oceans are storage tanks that dampen the winter cold with the accumulated summer heat or bring heat to Europe via the Gulf Stream. Even when it evaporates, water draws a lot of heat from the environment and generates evaporative cooling there. With the winds, latent heat is drawn from the tropics around the globe, only to be felt again where the moisture aggregates to form raindrops.

Water has a very high melting and boiling point. A comparison with its closest relatives, hydrogen sulphide and selenium, shows that H2O is an eccentric: plus 100 degrees Celsius (H2O), minus 60 degrees (H2S), minus 41 degrees (H2Se). As the lightest of the three compounds, water would have to change into the gas phase at minus 80 degrees. But it doesn't. Also bizarre what happens when you put water under pressure. Normal substances then become more viscous, while water becomes thinner. Normal liquids can also be compressed less and less, the colder they are. But water is becoming more and more compressible.

Thick or thin: who cares? Not just quirky theorists, but also biologists and physicians. Because in the cells water is the medium of all biochemical processes. If you want to understand them, you have to understand water. It is becoming increasingly clear that the world of proteins with their biocatalysts (enzymes) only works because water is the way it is. Only in it can proteins fold and unfold. In this world, even the smallest anomalies are crucial. Water is - here the well-worn vocabulary is allowed - the elixir of life par excellence.

The chemist Martin Chaplin of London South Bank University has compiled dozens of anomalies and says: "The small size of its molecule belies the complexity of its activities and its unique abilities." Alfons Geiger, Professor of Physical Chemistry at the University of Dortmund, adds, with a view to its function as a life medium: "Every new property of water that is discovered has long since been exploited by biological systems and generally by nature." New peculiarities are constantly becoming known.