It sounds like one of those quirky science questions every kid should know the answer to: Why does hot water sometimes freeze faster than cold water? In reality, not even the kids at the UK's Royal Society of Chemistry know—and they're offering a $1,600 prize to anyone who can tell them. The phenomenon, dubbed the Mpemba Effect, has been puzzling thinkers since Aristotle and Descartes, the society's president tells the Telegraph.
"Ice cream makers and bartenders alike use the fact … every day in their work, but no one really knows why it works," he says. The public has four weeks to submit scientifically plausible answers. If no one manages it, some of the UK's top young scientists will take on the challenge as part of the Hermes 2012 conference in London, which will coincide with the first week of the Olympics.