We’re talking about the carbon cycle and the production of fossil fuels, so I though it would be interesting to try extracting oils from plants, to demonstrate that it can be done. So one of my small groups put together a steam distillation apparatus using stuff that we had at hand and a length of copper tubing that we picked up at the hardware store.
We tried extracting the essential oils from lemon balm, because it grows like a weed here and even this early in the spring I have too much of it in the back yard (the middle school does not yet have an herb garden).
The distiller apparatus worked fairly well itself. Our improvised cooling chamber was a towel with ice in it draped over the copper tube. The melted ice-water would wick up the towel and evaporate as the water cooled the copper tube. You could see the steam rising off the the towel, an excellent example of phase changes in water resulting from transfers of energy.
We did not get any nice oil separation in the distillate, probably because we did not use enough lemon balm, but we got wonderfully fragrant water (in the flask on the left side of the picture). The water left behind in the pot also turned an ugly brown and looked a bit like crude oil (or tea) at least in a test tube.