MILAN – Of all the substances present on Earth, water is probably the only one of which everyone knows the chemical formula: H2O. Water is a common, daily and elementary substance (a small molecule made of just three atoms bound together to form a microscopic V).
It seems not to be hiding any grand mysteries, but rather surprising ones and, according to scientific writer Philip Ball, it violates all the rules. Which ones?
Alok Jha unveils all the surprises, mysteries and extraordinary facets of water in the volume "The Book of Water. The extraordinary story of our most ordinary substance" (Bollati Boringhieri).
What are some examples of the typical oddities of the most common liquid on Earth? Solid water floats on liquid water (ice floats on water) No other molecule does this.
The mysterious molecule
Hot water freezes faster than cold water. It seems to be a contradiction, yet this is what happens and the so-called “Mpemba effect” phenomenon takes its name from a small greedy Tanzanian boy who made his ice creams by putting the still boiling sweetened milk into the freezer.
The mere fact that the H2O molecule at room temperature and normal pressure is a liquid is already something surprising in itself.
Hydrogen sulphide, which has a very similar chemical formula (H2S), is a gas, despite having double the molecular weight compared to water; ammonia (NH3) and hydrochloric acid (HCl) have molecules of a similar dimension to H2O, and yet they are gases.
The phases of water
Just like other molecules, water has a liquid phase (water), a gaseous phase (water vapour) and a solid phase (ice). Only one solid phase? No: There are as many as 16 solid phases of water known today. Sixteen different forms of crystallisation, of which ice (known as Ih) is only the most common.
Water is an incredibly “sticky” substance. And it is precisely thanks to this high surface tension that life on Earth exists (if this were not so, the roots of the trees could not take water from the ground, for a start).
Virtually all compounds dissolve in water. Water interacts with everything that it comes into contact with and over time is therefore one of the most corrosive substances there is.
Alok Jha, a trained physicist and scientific correspondent of the "Guardian", works for the British television channel ITV. Also active for the BBC, Alok Jha has received the scientific writing award from the American Institute of Physics in 2014 and was named European Scientific Writer of the year in 2008. He published “50 Ways the World Could End: The Doomsday Handbook” (2014)
by Salvatore Galeone
January 24, 2018