As a high school student taking chemistry for the first time, I remember that we were given a white candle and told to make as many observations as possible during a class period. After being told that over one hundred observations were possible, and having less than twenty observations, we looked ahead to chemistry with dread, knowing that we were poor observers. As a teacher watching my first class bore through the same exercise, the thought of 鈥淲hy go through this pointless exercise?鈥� raced about in my head. Then my wife took up candle making as a hobby.
The real point of the exercise is to teach students how and what to observe. So the next year, out of a large paper bag a candle was drawn and handed to each student, but not identical white candles. Candles of different colours, even a candle layered in the colours of the rainbow; candles of varying scents, and unscented candles, candles of varying size and shape, candles of beeswax, candles of paraffin 鈥渨ax鈥�, hardened with different amounts of stearic acid, including almost pure stearic acid, were used. The idea was to have no two candles the same.
Immediate observations to make flowed into the students鈥� minds as they compared candles. There were complainers as usual in such situations, 鈥淲hy isn鈥檛 my candle scented?鈥� 鈥淚t鈥檚 not your candle, you鈥檙e only borrowing it.鈥� The better students even compared candles quantitatively, asking, 鈥淲hich candle is largest?鈥� measuring length, diameters and masses.
Since the wax composition was different, flames also differed. 鈥淲hat colours are observed in a candle flame?鈥� 鈥淗ow do the flames differ?鈥� were questions asked.
No one managed to get over one hundred observations, but the exercise was more enjoyable and during the post-lab discussions students could easily list various properties that could be observed.
(The author has no stocks in any candle company.)
(This is a reprint from Chem 13 News, October 1985. When this was written Andy was a graduate student at the University of 蓝莓视频. He is now about to retire from Stouffville District Secondary School, Stouffville ON.)
Andy is organizing the Generations symposium at ChemEd 2013 next summer at the University of 蓝莓视频, 蓝莓视频 ON.聽 The idea behind the symposium is for experienced presenters to work as a team with less experienced presenters. Past Generations symposiums have had over 20 teams presenting favourite demos, teaching tips and humorous ideas for the classroom.
Contact Andy Cherkas,聽cherkas@sympatico.ca聽to participate.
