Science of Water : Concepts and Applications

All about Water 13
discovered a few years earlier by his colleague, the English chemist and clergyman Joseph Priestly,
who, fi nding that it kept a mouse alive and supported combustion, called it vital air.
JUST TWO H’S AND ONE O
Cavendish was able to separate the two main constituents that make up water. All that remained
was for him to put the ingredients back together again. He accomplished this by mixing a measured
volume of infl ammable air with different volumes of its vital counterpart, and setting fi re to both.
He found that most mixtures burned well enough, but when the proportions were precisely two to
one, there was an explosion and the walls of his test tubes were covered with liquid droplets. He
quickly identifi ed these as water.
Cavendish made an announcement: Water was not water. Moreover, water is not just an odorless,
colorless, and tasteless substance that lies beyond the reach of chemical analysis. Water is
not an element in its own right, but a compound of two independent elements, one a supporter of
combustion and the other combustible. When united, these two elements become the preeminent
quencher of thirst and fl ames.
It is interesting to note that a few years later, the great French genius Antoine Lavoisier tied
the compound neatly together by renaming the ingredients hydrogen—“the water producer”—and
oxygen. In a fi tting tribute to his guillotined corpse (he was a victim of the French Revolution), his
tombstone came to carry a simple and telling epitaph, a fi tting tribute to the father of a new age in
chemistry—just two H’s and one O.
SOMEWHERE BETWEEN 0 AND 105°
We take water for granted now. Every high-school level student knows that water is a chemical compound
of two simple and abundant elements. And yet scientists continue to argue the merits of rival
theories on the structure of water. The fact is we still know only little about water. For example, we
don’t know how water works.
Part of the problem lies in the fact that no one has ever seen a water molecule. It is true that we
have theoretical diagrams and equations. We also have a disarmingly simple formula—H 2 O. The
reality, however, is that water is very complex. X-rays, for example, have shown that the atoms in
water are intricately laced.
It has been said over and over again that water is special, strange, and different. Water is also
almost indestructible. Sure, we know that electrolysis can separate water atoms, but we also know that
once they get together again they must be heated up to more than 2900°C to separate them again.
Water is also idiosyncratic. This can be seen in the way in which the two atoms of hydrogen in
a water molecule (see Figure 2.1) take up a very precise and strange (different) alignment to each
FIGURE 2.1 Molecule of water.
H +
H +