A weird silvery-transparent liquid; tasteless, formless, expressionless, and yet it lights up the hearts of millions. It can be benevolent and invigorating at its calmest, and veritably malevolent at its most acrimonious. Indeed it is most capable of scalding, freezing and swift brutality. And yet, its caressing feel will mollify even the most of parched of lips. Constituting 70% of our beloved Earth and 60% of us, this liquid goes by the name of dihydrogen oxide; water to you and me.
Water is unlike any other chemical in our varied universe; indeed, it flummoxes even the best of us. Water seems to be asininely unaware of the laws of nature.
If you were to look at water’s cousins (namely hydrogen compounds with elements under the same group as oxygen in the periodic table; they generally have similar properties), e.g., hydrogen selenium and hydrogen sulphide and predict its properties—you would be forgiven to cerebrate that water would be a liquid at sub-zero temperatures, boil at -93⁰C and exist as a gas at room temperature. It is truly a unique character indeed, because in reality, it behaves nothing like this.
Cool water down and it starts to innocuously contract (decrease in volume and increase in density); just like a normal liquid should. But, after 4⁰C it springs back up and expands almost feverishly, becoming less dense. This beguiling fact means that solid form of water, ice, paradoxically floats on water. This obviously has immense consequences; not least the fact that it stops water bodies from freezing completely, and destroying all sea life.
When a water body is cooled down, its top layer freezes first. Now since ice is lighter that water, the top layer of ice floats on the surface. This effectively insulates the water below from any temperate change, thus sparing the sea creatures in the water from a frosty death.
Perhaps more amazing than this is that all these watery absurdities can be elegantly explained with a single stroke of chemical ingenuity: the hydrogen bond. Let’s see how.
Take a look at the structure of water.
Two hydrogen atoms share electrons with an oxygen atom in the proverbial covalent bond. But, this sharing is not all fair play. Oxygen is promiscuously greedy; edging the electrons more towards it. This makes oxygen negatively charged and hydrogen positively charged. A charge separation is created and hence; water is a polar molecule.
The two positively charged hydrogen atoms provide an irresistible treat to any negatively charged atom, including an oxygen atom from another water molecule—which indeed is negative. Thus, an oxygen atom of one water molecule sort of binds with hydrogen of another, producing that most crucial hydrogen bond.
This changes everything. Hydrogen bonds attract water molecules towards each other; it bands them together. Consequently, this allows water to exist as a liquid when most of its brethren would be floating away as gases.
Water molecules engage in a kind of dance; bonding with other molecules and letting go, then only to bond with other water molecules. This dynamic swapping of partners is happening all the time; even in the most insipid of water bodies. Just take a look at a simple glass of water; can you see the water molecules dancing?
The strength of hydrogen bond is crucially important. For it was off by just a few percent either way; water would exist as a gas or a solid. Hydrogen bonding—it appears—should be tight, but not too tight.
Another untenable property of this untenable substance is that, due to its polar nature, it can dissolve almost anything. In fact, water is the de facto solvent; the universal solvent.
To remark that this property is vital for life is a gross understatement. Virtually all biological activities happen in solution, in water. The movement of ions, the metabolic cycles, the folding of proteins, the catalytic activities of enzymes and the list goes on and on. It is hence that water is pertinent to all living systems on Earth. Indeed, most inorganic reactions conducted in a lab are in solution as well.
As if these properties were not prodigious enough, there is more. Water has a high specific heat capacity, which means that it can hold a lot of heat. On the small scale, this creates that soothing sea breeze; on the large scale, it barricades much of the Northern Hemisphere from retreating into another ice age.
Frozen water—or ice as it is more commonly known—present in large amounts at the poles may seem discreetly removed from us, but mind you, it’s anything but. It is a big player in our global climate. Ice has the property of reflecting sunlight and heat and regulating Earth’s temperature. If the ice were to melt (by global warming), it would create many ill effects indeed; effects we are alarmingly starting to experience.
It would create untold flooding, devastation and in the process raise global temperatures. And maybe therein lies the more cloistered, insidious side of water; a side we are increasingly going to encounter.
Such is the curios of this liquid we call water. It would be a notoriously difficult task to imagine life without it. Indeed, it would be befuddle us thoroughly if we were to discover an ecosystem independent of water. But we haven’t yet, so the platitude for extraterrestrial life seekers ‘follow the water’ ostensibly still stands.