Thirty five years ago I first taught science in a secondary modern school in Salford.
I did the experiment of burning a candle in a bell jar. In fact we all did. The rule of the day was Nuffield Science and that meant the kids getting stuck in - fingers and hair burnt, trousers and skirts soaked!
After we had performed the experiment and cleaned up we discussed what our conclusion should be. Although damned by the 11 plus the kids were not stupid and realised that something had been used up as the candle burned out and the water level in the bell jar rose.
At that point I was able to pull the rabbit out of the hat and explain that oxygen, roughly a fifth of the air we breathe, had been consumed by the candle....... de daaan!
Terry Burke, a dear friend and head of department, took me on one
side and asked me what I thought had happened in the experiment. (He often hovered at the back of the class or in the prep. room to make sure I got out alive. ) I repeated my explanation. Terry suggested that I consider the chemistry. For each molecule of oxygen burnt from the air one molecule of carbon dioxide was produced. So one molecule of gas reacts with a vaporised solid to produce one molecule of gas............. oops! Terry said that it was probably the case that the carbon dioxide, more soluble than oxygen, was immediately dissolved in the water.
I think you would have liked Terry, he always new the right questions to ask.
Keep asking the right questions!
