Ok, now I know it may have been hard to see, but here is what happened. I took a glass of melted butter, and a glass of water, liquid forms of both. Then I dropped in a piece of the same stuff, only in solid form! When I put the solid butter in the liquid butter, it sank to the bottom, right? But when I put the solid water (ice) in the liquid water, it floated!
First, lets remember that water molecules are made from 1 oxygen atom, and 2 hydrogen atoms (H2O). They form together via a chemical bond that happens when they share electrons. As we learned in my science post (Water as a Solvent), water molecules are polar molecules, because the electrons are uneven. So the hydrogen atoms have less then their share of electrons so when they get close to other water molecules they try to take electrons from the other oxygen molecules who have more then their fair share of electrons. But there are not enough electrons to form chemical bonds, so they form hydrogen bonds, which are similar, but very weak. See my example below.
See how the hydrogen atoms turn so they can connect with other oxygen atoms? Chemical bonds take atoms and link them together to make molecules, and hydrogen bonds take molecules and link them together. There you are; hydrogen bonds.
When water is frozen, the molecules cannot form hydrogen bonds, so it is not held together as well. So when I put the ice in the glass of water, it floated because the water bond was strong enough to hold up the ice. But butter is just the opposite, it is stronger when it is cold, and when you heat it the molecules pull apart. So when I dropped the solid butter in the liquid butter, it was able to push its way through the weaker hot butter, and sink to the bottom.
Now, lets take a look at what this bond does, lets start with looking at some other similar compounds. There are many chemical compounds that are very similar to water from a scientific view point, take hydrogen selenide, (H2Se). It has two hydrogen molecules, just like water, but instead of an oxygen atom, it has a selenium atom. This chemical formula is a gas at room temperature, and its boiling point is -41.25*C as opposed to waters' 100*C. The key difference? H2Se has no oxygen to form hydrogen bonds, therefor it won't hold together! The same goes for H2S and H2Te. All are very similar to water, but they are gases instead of liquids. Isopropyl alcohol (common rubbing alcohol) is very similar to water, its' chemical formula is C3H8O. See how it has hydrogen and oxygen? That is why it can stay liquid as well, the bond just is not as strong as in water.
So we know what hydrogen bonds are, and we know how they work, but why does it matter? Think about it. If water could not form hydrogen bonds, then it would become a gas, and we could not drink it, or use it at all! Think about a lake are a pond in winter. When the water freezes it floats to the top, then it insulates the rest of the water, so that not all the water freezes, and the things living in the pond don't die! If it were not for hydrogen bonds, water would not be as it is, plants could not grow, would die, and the earth would be unable to support life! This small simple matter is so vital for our very survival! Yet somehow God sees fit to bestow us the blessing of life and hydrogen bonding. What a great God he is.
Well, I hope you learned something interesting. I next time you go to drink a tall glass of ice water, think about those little molecules, working to keep us hydrated!
Have a great September!
-Kat
To learn more about hydrogen bonding see Dr. Jay L Wiles' book Exploring Creation with Physical Science, module 4 pages 93-97. And check out all the cool chemical formulas at wikipedia.org.
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