Find out why warm beer goes flat and divers need to pause before they resurface.
A while back there was an entry about how most water, which looks so pure and clean, is actually a filthy mess of tiny solid particles. That's what helps it boil, when it's heated up on the stove. Vaporization sites form around the filth.
Not only does drinking water mean you're consuming solid dirt, but it also means you're chugging down whatever stray gases get mixed up in a liquid too. Most liquids, even the ones that look cool and sedate, are a frothy mix of liquid, solid particles, and dissolved gas.
Just how much of each is in the liquid depends on a lot of factors. Each liquid has its own tolerance for different particles, but that tolerance varies according to conditions. The variance of these conditions presents problems, from the minor – flat beer – to the major – medical problems and death.
Low temperature makes it a lot easier for gas to remain dissolved in liquids, which is why most carbonated beverages are served cold. The molecules in cold beer aren't moving very fast, and aren't likely to jostle gas loose from the water. As they warm, more and more gas molecules escape as tiny bubbles, and what's left is a lukewarm glass of yellow water.
Which is a lot better than what happens under low pressure, at least for divers. A way to push gas into liquid, when the temperature doesn't go down, is simple pressure. Certain liquids are especially adapted for carrying gases: blood, for example. One of its main jobs is to ferry oxygen around the body. Of course, it carries other gases, too. Nitrogen is what makes up most of earth's atmosphere, and at atmospheric pressure, the blood carries a great deal of dissolved nitrogen around. As a diver goes lower in water, more and more pressure is applied to the body. High pressure pushes more dissolved nitrogen into the blood.
This sounds like a huge problem, but surprisingly enough, it doesn't do damage. At least, not in the short term. The trouble comes when it's time to get the gas out again. Gradual reductions in pressure let it safely work its way out of the bloodstream. A huge lift in pressure and it's like someone popped open a can of soda. Bubbles form in the blood stream and travel through the body, resulting in rashes, fever, paralysis, death, and many other symptoms which remind us that it isn't good to have blood like soda pop. This is why divers make stops at certain depths to let their bodies get re-adjusted to regular atmospheric pressure.
(It is, however, good to have ice cream or sorbet like soda pop. Any people who wish to carbonate something, shove it in a mostly-sealed container with dry ice and wait until the ice evaporates. Fruit should be over a layer of paper towels. Liquid can be loose. Ice cream is best if it's kept in its cardboard container. The gas will push through. When it's fizzed through, grab some spoons and start eating.)
Via The Big Site of Amazing Facts, eHow, Wise Geek, and About.com.