"Last month (March 2012), Alan Alda and the Center for Communicating Science asked scientists to answer the question – “What is a flame?” – in a way that an 11-year-old would find intelligible and maybe even fun." There were 822 entries from 31 countries by the deadline. They came as sentences, poems, pages of prose, videos and animations. After being screened for accuracy by scientists, the entries were sent to more than 130 schools, where 11-year-olds judged them. (link)
You can see the finalists on this page. In the winning entry, below. a friendly scientist explains fire to a man chained in hell.
In this video podcast from Science Friday, Alan Alda talks about the Flame Challenge.