If hot water rises, why does ice form on the top of water than the bottom?
In: Chemistry
Water is different from most substances because when it freezes, it does so in a crystal structure. That is, the water molecules form a specific shape with a lot of empty space in between, meaning ice is actually lighter than water.
The reason that hot water rises is simply because its less dense or lighter than cold water, but because of that crystal shape, ice is actually even less dense or lighter than much warmer water. This means that when you have a larger body of water, like a lake or pond or even a swimming pool, the ice crystals will rise to the surface as they form instead of sinking to the bottom. The ice on top also acts as an insulator, preventing the water underneath from freezing as easily.
This is important, as without this unusual quality of water, all bodies of water would freeze solid during the winter killing off all aquatic life immediately, and leave no liquid water for terrestrial life. The Earth would end up covered in glaciers too as there would be so much ice that even summer would be enough to melt it. Maybe the tropical regions would still have liquid water. I’m not even certain of that, as all that ice would also lower the global temperature.
So be thankful for the odd way that ice freezes!
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