Wednesday, March 16, 2011
The Most Extraordinary Ordinary
Water. A thing we see everyday in our life. Ice. Another thing we see everyday... well almost everyday. But have you ever thought about how strange ice are water are? I mean ice is the only thing that floats in its solid form. Like butter sinks in melted butter and like copper would sink in liquid copper. Ice, it floats! I know it has something to do with water's structure, but i just don't understand it. I mean when water becomes ice, the density changes from about one to 0.92. I think it has something to do with the water expanding when it freezes, but I'm not sure. Any thoughts?
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Water is special because it is polar (you know, just like the carbonyl group!). The oxygen is more negatively charged, and the hydrogens are more positively charged. So water can make "hydrogen bonds" with itself by matching positive with negative.
ReplyDeleteAt lower temperatures, the water molecules aren't moving as fast, so they can make these hydrogen bonds more easily. Eventually,at 0 degrees Celsius, water freezes to form a structure with lots of hydrogen bonds. When this structure is formed, the atoms of water are fixed in place by the hydrogen bonds, which separates them more than if they were moving all around. That's why ice is less dense than water! And that's why water expands when it freezes.
Interesting, and useful, isn't it? Hydrogen bonds are super important! They hold our DNA together as well! We have to consider their effects a lot in organic chemistry. ;).