To hell with the dog, water is man's best friend. Or to be more accurate, Life's. Most humans, in our continuing attempt to understand everything, have a pretty good grasp on water. Its wet, things float on top of it, it turns to gas at 100 degrees C, freezes at 0, and is quite refreshing as well. Plants understand water too, even if they can't verbalize the reasons. Water's adhesive properties pull it up an inch tall grass stalk or a 300 foot tree in the same fashion.

But there is one facet of water's story where most seem to be uninformed. Under some circumstances, hot water freezes faster than cold does. Yes, read the sentence again. This phenomenon, known as the Mpemba Effect, is not a joke, and is named after the tanzanian teenager who was the first modern scientist to describe the process.

The Mpemba Effect seems to fly in the face of the basic rules governing gradients and on the surface, the Mpemba Effect makes no sense at all. How can something warmer freeze faster? How can all those bouncing water molecules become sedated more quickly than their less hyperactive friends? To fully grasp the explanation, one needs to get into a tortoise and hare mentality. This doesn't mean that slow and steady always wins the race, just that there can be other, less apparent details underlying a seemingly transparent process (that hare was fast, but he sure had some issues with focus.) So open your mind for a minute and see if you can wrap your head around this one.

In addition to faster moving molecules, warmer water has another important attribute. All water contains dissolved gasses (its this fact that allows fish to breath) and the percentage of gas decreases as the temperature of water increases. Water's freezing process is the gradual organization of its molecules into a solid lattice. Like trying to play a game of Jenga with a few legos thrown into the pile of rectangular wooden blocks, dissolved gasses slow down the construction of the ordered castle that is an ice crystal. This difference is enough to give slightly warmer water and advantage in the freezing race.

Convection currents are also thought to play a role in this odd occurance. In this respect, the explanations are a little more sketchy. In some containers, warmer water creates temperature currents that actually cool the liquid more rapidly than cooler water, which might not have such circulation.

Finally, evaporation can also come into play. Warmer water will be more likely to evaporate when two identical containers holding water of different temperatures are placed in the freezer. This evaporation could reduce the total volume of the warmer water, allowing it to freeze faster. Any referee would easily dub this cheating, but its hard to figure out a way to control for evaporation in an experiment comparing freezing rates.

By this point you should see that the initial statement about hot water freezing faster was somewhat sensationalized. Like most science, its usually hard to some up the whole bag into a catch-phrase. Clearly, water at 99.9 degrees will not freeze faster than water at 0.1. However, the reasoning above begins to describe how this counterintuitive effect could be true in some circumstances. Demonstrating the Mpemba Effect is not trivial either, leaving many high-school lab attempts a wash, causing students to leave with the wrong message. Although its hardly the hottest field in science, researchers are still struggling to completely understand. The phenomenon is surprising, but we must remember that we are dealing with water here, perhaps the most amazing substance in the universe; if only because the word "amazing" may never have been invented without it.

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