I'm going to be teaching unit 4C Keeping Warm. It says that metal is a bad thermal insulator but when I did this previously the kids got the result that tin foil kept a beaker of water the hottest. Thinking about it, foil refects the heat back in even though I know it is also conducting it away. Also, the hottest take away you can get is always Chinese food which comes in foil containers. It's always much hotter than pizza or chips in card or paper wrapping. I expect I'm being really thick about this but please let me know what the rest of you think. Could tin foil keep beakers of water warmer than card?