Water and Life

2004-06-06T16:10:00Z

In water the angle formed by the hydrogen atoms and the oxygen atom is 104.5. It is my understanding that this angle is responsible for ice being less dense than liquid water. The fact that ice floats on top of water plays an important part in allowing life as we know it to exist.

Water is a fairly common molecule, but the fact that it is less dense in its solid state is very unusual. So, why is there an abundant, very strange, life giving molecule in the universe? In other words, why is there a 104.5 angle in the water molecule?

One friend suggested the angle would like to be a 90 angle, but the hydrogen atoms are repelled from each other, and the angle is widened. This seems reasonable, but why would the hydrogen be inclined to be bonded at a 90 angle? By symmetry, it seems like they would want to be bonded at a 180 angle. How senstsensitive is the low density ice property of water to the 104.5 angle? How much would the electromagnetic force need to be change so that water density would behave normally, and life as we know it wouldn’t exist?

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