I have never used this object as a lesson in and of itself. As Halloween nears, I do not do a “Halloween Lesson” per se. But I will do a “scary” lesson. Typically, I have everything set up on a table in front of the class in a room that can be made completely dark. On either end of the table I have a clear glass container that can hold about a gallon of water. Dead center is placed a silver candelabra with five tall white candles. On cue, the lights go out, and a recording of the theme music from “Phantom of the Opera” begins playing at a fairly high volume. The center candle is then lit, allowing me to see a little better. From behind me, I bring forward a water thermos filled with the hottest water I can find, and pour it into the two glass containers, filling them to within an inch of the lip. Also from behind me in a cooler, I pick up a piece of dry ice and gently drop it into the container of hot water. Doing it a second time for the other container and both are then bubbling and producing a table hugging fog that flows across and drops off of the table. Then the remaining 4 candles are lit and I gradually turn the music down. By this time, I guarantee you will have their attention and can simply have a few moments of quiet, allowing them to listen to the ice boiling in the water and watch the fog roll off the table edges. Then start your lesson, teaching the entire lesson in the darkened room.