Sian, that reminds me of school. When the teacher was talking, I used to enjoy mucking around tipping chemicals from our experiments from one test tube to another to see what colour they turned. All was fine until one day (I think we were doing esters at the time) I managed to mix conc sulphuric acid with sodium hydroxide. The test tube exploded and I spent the next 20 minutes having water poured on my face by a worried teacher. On reflection,I was extemely lucky that no damage was done!