It’s one of the most fundamental compounds on Earth, and it makes up roughly 60 percent of the human body, and yet water is turning out to be stranger than we could have ever imagined.
Researchers have been investigating the physical properties of water, and found that when it’s heated to between 40 and 60 degrees Celsius, it hits a ‘crossover temperature’, and appears to start switching between two different states of liquid.
As a chemical compound, water is so vital to life on Earth, we’ve been underestimating how legitimately weird it is.
We’ve all gotten so used to it, it’s hard to imagine things getting any more complex than the three basic states: solid, liquid, gas. (Under very rare circumstances, a plasma-like state can also form.)
But in many ways, plain, old water is unlike any other substance on the planet.
With the exception of Mercury, water has the highest surface tension of all liquids. It’s also one of the only known substances whose solid state can float on its liquid state, and unlike almost every other known substance, water expands when it freezes.
It also has a bizarre boiling point. While the boiling points of other hydrides, such as hydrogen telluride and hydrogen sulphide, decrease as their molecule size decreases, H2O has a surprisingly large boiling point for such a small molecular weight.
“No one really understands water,” Philip Ball points out in Nature. “It’s embarrassing to admit it, but the stuff that covers two-thirds of our planet is still a mystery. Worse, the more we look, the more the problems accumulate: new techniques probing deeper into the molecular architecture of liquid water are throwing up more puzzles.”
Now physicists have demonstrated that somewhere between the temperatures of 40 and 60 degrees Celsius (104 and 140 degrees Fahrenheit), liquid water can ‘switch’ states, exhibiting a whole new set of properties depending on the state it flips to.
To figure this out, an international team led by physicist Laura Maestro from the University of Oxford in the UK looked at a number of specific properties of water.
They looked at things like thermal conductivity, refractive index, conductivity, surface tension, and the dielectric constant – how well an electric field can spread through a substance – and how they responded to fluctuations in temperature between 0 and 100 degrees Celsius.