Explaining water's weirdness
Water covers more than two thirds of our planet, makes up 60 percent of our bodies, and sustains our lives and lifestyles in countless ways. Although simple H2O may seem like the most ordinary substance in the world, it's actually one of the strangest. Almost every other liquid contracts as it approaches its freezing point, but water expands as it freezes. If most liquids are supercooled, so that they remain liquid below their freezing temperatures, their capacity to absorb heat decreases–but water's skyrockets. Likewise, the compressibility of most liquids doesn't change when they're supercooled, but water's compressibility shoots up.