This is the personal blog of alisonraymond

Funny how we fickle humans invest value in what is rare just because it is not easily obtained and dismiss the common as dull just because of its ubiquity. Take carbon for example. The very same carbon atoms can be assembled to form a piece of charcoal worth a few pence, a diamond of such value that men are prepared to kill and to risk being killed just to possess it or, with the addition of a few other kinds of atoms, the tissues of a living organism. Expose any one of these forms of carbon to high temperatures in an atmosphere rich in oxygen and the result is the same...Carbon Dioxide gas...the diamond, the charcoal and the flesh equal in their moment of destruction!

But, it is another substance which, although very common, I want to nominate for the chemistry prize for weirdness and that is plain, ordinary water, l’eau, l’agua, Adam’s ale.
A simple compound formed by the oxidation of hydrogen, and that’s weird for a start! You burn hydrogen, which blazes very nicely thank you, and you make water, for many purposes still the principle means by which a fire might be extinguished! If you doubt this then just look at the kitchen windows after cooking with gas on a winter’s day...”Aha” you say “I’ve been boiling the sprouts so obviously some of the water has evaporated and condensed on the cold windows!” True, so, in the pursuit of good science do the same experiment when you are roasting, no steam now, but still plenty of condensation!

Adam’s ale?
I wonder if the person who coined the term realised that there is a very real sense in which water can be regarded as pure alcohol?
Oh, but it’s true! Consider the chemistry of the group of chemicals which we call alcohols. Lets start with propanol. Molecules of this fragrant liquid comprise three atoms of carbon surrounded by a cluster of seven hydrogen atoms and a pair called a hydroxyl group, containing one oxygen and one more hydrogen atom. Next down the group is ethanol. This is the main active constituent of the intoxicating beverages. Each molecule has two carbon atoms, five hydrogens and the trusty hydroxyl group. Next, welcome methanol. Highly toxic, it has just the one carbon three hydrogen and, you’ve guessed it! Harriet hydroxyl.
Ok so far? Right, let’s take away the last carbon atom and see what’s left. Oh! It looks like our hydroxyl group has teamed up with a spare hydrogen! Yep, its H – OH better know by the shorthand H2O
... just a half for me thanks.

But just what does water think it is? I mean, it’s a titchy little molecule that looks like a silhouette of mickey mouse’s head. It’s got a couple of lightweight hydrogen atoms stuck on the side of an oxygen atom and yet it slops around as a liquid at temperatures between 0 and 100 celcius at sea level. Why isn’t it a gas like other similar low molecular weight compounds? Hydrogen sulphide for example has a very similar formula (H2S), but it is a gas. Foul smelling, highly toxic and best avoided...and the list goes on...carbon dioxide gas, nitrogen dioxide gas, hydrogen chloride gas...all relatively heavy molecules which are none the less delighted to dance around the place as gases! So why does water seem happy to stay at the bottom of a glass like some party pooper who hangs around the kitchen all night?
Well, it seems that water is, well, wet because of a very peculiar phenomenon. You see, hydrogen atoms have the strange ability to cling rather feebly to certain other atoms in certain conditions and one such circumstance allows the hydrogen atoms in a molecule of water to link to the oxygens in neighbouring molecules. The result is that the molecules in water are loosely knitted together. This effect called ‘hydrogen bonding’ restricts the opportunities for individual molecules to fly off into space so spilled water forms a puddle which only slowly evaporates. Which is a bit of luck for all us organic life forms since liquid water shows every sign of being a fundamental prerequisite for our existence.

I don’t want to over egg the weirdness pudding. Both eggs and puddings deriving their natures in part at least from the eccentricities of water, but there is one more thing to be considered!

It is weird that ice floats in water!

Didn’t we all learn in school that matter expands when heated and contracts when cooled? So surely, ice being cooler than water, it should undergo a degree of contraction. This in turn should increase its density and my gold fish pond should freeze from the bottom up on a winter’s night and the Titanic should have passed safely over the iceberg which was bumping along the ocean floor far far below!
Once again it is the water molecule and it’s inclination to hydrogen bonding which provides an explanation.

You see, ice is a crystal, and in crystals the particles, in this case molecules of water, are stacked together in neat, orderly patterns. Look at some salt with a magnifying lens and you will notice that each grain is a tiny cube reflecting the cubic arrangement of the particles. Inspect a snowflake in the same way, whilst holding your breath to avoid melting it, and you will observe that every individual flake has a six sided symmetry in testament to the pattern adopted at a molecular level. As ice forms the water molecules assemble into their ranks as the crystal grows, but to accommodate the shape of the molecules and their hydrogen bonding the individual particles end up being a little more separated than they were as free liquid particles. Consequently, water as a solid has the very unusual characteristic of being less dense than in its liquid form, and ice floats.
This is very good news not only for Torville and Dean but also for life on Planet Earth, since if water were more normal in its properties then the oceans would have frozen from bottom to top during the colder times in Earth history. Such conditions would have rendered both the origin and the continued maintenance of life quite out of the question.

So, as you boil the kettle or rattle an ice cube in a glass of something refreshing spare a thought for water, it is amazing stuff and we in temperate lands are truly blessed to have so much of it readily available.