I heated up something which was flammable a bit too quickly and caused a fire in the furnace. It was contained because it was inside a ceramic lining but there was masses of smoke and we have to evacuate 🙁
Not horrifically wrong, but quite wrong! It was actually at a science fair and my group were showing how acid rain worked, but we melted one of the tubes in the experiment with a Bunsen burner. I don’t think the judges were too impressed!