If you take two bodies of water, identical in all parameters, except in temperature, and put them in a freezer, initially hot water will freeze faster than cold water. I know, it seems just wrong, and yet even if this effect appears impossible at first sight, it has been verify in many experiments and throughout history many famous natural philosophers, including Aristotle, Francis Bacon and Descartes, have talked about it in their works.
The effect was reintroduced to the XX century scientific community by a secondary school student from Africa. In 1963 Erasto Mpemba realised that hotter liquids freeze faster than cold ones while he was making ice-cream at school. When he asked his teacher about this incredible phenomenon he told Mpemba that he was wrong. But the young scientist didn’t give up and when he had the opportunity he asked a professor of Physics from a local university. Dr Osborne did not have an answer, but believed Mpemba when he said that he had seen it happening and promised that he would have repeated the experiment. After the academic saw it happening with his own eyes he wrote a paper and from that moment this phenomenon is known to the world as the Mpemba effect.
We still don’t have a real and complete explanation, and for this reason the Royal Society of Chemistry has launched a competition offering 1000£ for a scientifically sound and creatively presented explanation. The competition has been organised with scientists from the Hermes 2012 summer school on material modelling, 60 bright young minds that will also try to find and explanation for the Mpemba effect.
The RSC and Hermes 2012 have been overwhelmed with submissions and people from all around the world have submitted their ideas to explain the Mpemba effect. The response was so unexpected that there will be two winners, not just one. The first winner will be appointed by 100 experts while the second one will be selected by public vote after a first short listing.
The almost 22000 entries will soon be judged and the winners will be announced in January 2013.
With this competition the RSC hopes to foster interest in chemistry and scientific thinking in general. People will have to challenge a non intuitive phenomenon and embrace the scientific method, keeping their mind open, thinking scientifically to explain what they will see with experimental experience.