Water's Weirdness

There's an interesting article by Alok Jha in The Guardian on the very strange and unique properties of a substance we (unless we're Californians) take for granted - water.

It's hard to overstate how amazing water's properties are and how crucial those properties are to living things. For example, Jha tells us that,

Water is at its most dense at 4C and, at that temperature, will sink to the bottom of a lake or river. Because bodies of water freeze from the top down, fish, plants and other organisms will almost always have somewhere to survive during seasons of bitter cold, and be able to grow in size and number.

If the temperature of the water continues to drop toward 0C (the freezing point) the colder water actually gets less dense and rises to the surface. That's why ice floats. It's less dense than the warmer water it floats in.

In fact, if it didn't float it would sink to the bottom and bodies of water would freeze from the bottom up making it impossible for most forms of life to survive a cold winter.

Jha adds,

This, though, is just the start. Take a glass of water and look at it now. Perhaps the strangest thing about this colorless, odorless liquid is that it is a liquid at all. If water followed the rules, you would see nothing in that glass and our planet would have no oceans at all.

All of the water on Earth should exist as only vapor: part of a thick, muggy atmosphere sitting above an inhospitable, bone-dry surface. A water molecule is made from two very light atoms – hydrogen and oxygen – and, at the ambient conditions on the surface of the Earth, it should be a gas. Hydrogen sulfide (H2S), for example, is a gas, even though it is twice the molecular weight of water. Other similar-sized molecules – such as ammonia (NH3) and hydrogen chloride (HCl) – are also gases.

Of course if water were a gas at normal temperatures life as we know it would be impossible. Jha mentions a few other interesting facts about water, but he just touches the surface, as it were. Entire books have been written on the subject, and indeed, Jha himself has written one.

Here's one more fact that Jha didn't mention. Water gains and loses heat more slowly than almost any other substance. This is why the ocean is still cold even on a blistering hot day in June. It takes a long time for water to heat up and a long time for it to cool down.

This is very fortunate for a number of reasons but one is that because there's so much water on the earth's surface and because it changes temperature slowly it tends to stabilize the earth's overall temperature and keep it within a range in which life can thrive.

Water has lots of other properties that make it indispensible for life: Its very low viscosity, its ability to dissolve most other substances, its ability to adhere to surfaces and cohere to itself, its ability to exist in all three states at the same time, and many more unique properties, many of which are essential to living things.

Jha claims that evolution has shaped us to survive in a watery environment.

Perhaps so, although it's hard to imagine a life form that could exist in the absence of water, or perhaps the myriad fortuitous properties of water, so far from accidentally resulting from the mindless chaos of the initial Big Bang, are actually the deliberate result of the scientific genius of a brilliant cosmic Chemist.

This lovely 8 minute video emphasizes the uniqueness of water: