Flushed away: God and H2O

Originally published in November 2007

OK, pay attention to this one you might need to concentrate cos I'm going to have to explain some science and you need to keep up.

When I was in sixth form I did a Chemistry A level; which wasn't a total waste of time cos I can now read the ingredients list on the back of shampoo bottles.

Teaching my class chemistry must have been like swimming through custard as - apart from 3 oxbridge candidates - no-one was really that interested and only really took the subject to fill gaps in our timetables. Our teacher - Dr Jackson - battled on in the face of adversity and managed to hold it together until the year after we left school when he had a nervous breakdown and retired. There was the incident when one of our class had worn his trainers without socks all summer, then wore them for school. His feet smelt so dreadful that Dr Jackson had an asthma attack and we all tried to get sent out to get away from the stench. When we came to sit our mock exams we all failed (apart from the oxbridge set) and had letters sent home by Dr Jackson saying that unless we passed the re-sit he would kick us off the course. I was the only person who passed the re-sit and no-one got kicked off.

The syllabus was split into 3 sections - organic chemistry, non-organic chemistry and physical chemistry and it's this last section my story is concerned with. Unsurprisingly I can't really remember what physical chemistry is but it's something to do with the structure of molecules.

Ok, this is the sciency bit that you need to listen to. In a physical chemistry lesson and Dr Jackson's explaining the transition of states to us. In other words freezing. When a liquid freezes its molecules lose energy and gradually vibrate less and less. This means that they can sit closer together resulting in the volume of the substance shrinking which in turn means that it's density increases. The colder denser liquid sinks to the bottom of whatever's containing it and the liquid freezes from the bottom up.

Are you still with me? Good that's the simple bit.

There is one liquid, explained Dr Jackson, that doesn't behave like that and it's water. What happens with water is that it behaves perfectly normally as you cool it down to 4°C and then the molecules start to form hydrogen bonds between them. Hydrogen bonds (if my memory serves me correctly) aren't proper chemical bonds, but a loose magnetic attraction that holds molecules together. When water gets to below 4°C the hydrogen bonds start to form and they make a bit more space between the molecules resulting in the volume increasing, the colder liquid rising to the surface and water freezing from the top.

But this quirk in the properties of water is hugely significant, Dr Jackson went on to explain. Imagine if you will a lake in the middle of winter. As the air temperature drops it cools the water until the water starts to freeze. If water behaved like every other liquid the ice would form from the bottom of the lake and the layer would get thicker and thicker until the whole lake was completely frozen. Instead the ice forms at the top of the lake producing an insulating layer which prevents the water below it from freezing. This is vitally important for aquatic life as if water conformed to normal behavior and the entire lake froze everything in it, fish, insects, would freeze to death. Very little (apart from viruses and bacteria) would be able to survive and considering that science tells us that life began in the water if water behaved as every other liquid then the evolutionary chain would have been stopped before it had chance to get going. Life on this planet just wouldn't happen.

So just as we're sitting there actually listening to Dr Jackson for once and trying to take in what he'd just explained to us he carried on. "I'm an atheist," he told us. "But if any one thing was going to convince me of the existence of God it would be that; that this simple quirk, this inexplicable quirk in the properties of water is absolutely essential for the presence of life on this – or any – planet."

Then someone farted and broke the mood.