Mr. Gaar was my excellent ninth grade science teacher at Highland Junior High in Hobbs, NM. I recall that he had a quote posted above his blackboard that still has me thinking, a quote from Einstein: “Religion without science is blind. Science without religion is lame.”
One day, after giving us all an assignment that would keep us busy, he set up a demo on the lecture table. He started by taping together two funnels at their large end, like so, and placed this in a ring stand with the ends of the funnels pointing up and down. Then he set up a small hydrogen generator by pouring some HCl on some zinc chips in a bottle with a one-hole stopper, and attached a short length of hose between the bottle and the bottom of the lower funnel.
After a few minutes, the funnels were pretty much full of pure hydrogen. He lit a match and held it over the opening of the upper funnel. Hydrogen burns with a nearly invisible flame. Even from the front row of the classroom, I couldn't tell he had lit it.
A few minutes later he removed the hose from the lower funnel and went to the back of the classroom to yell at some students.
A short time later there was a loud bang, and some of the girls in the class screamed. The whole point of his demo was to provoke this response. Then he explained how it worked. When the funnels were full of pure hydrogen, the gas venting out of the top burned quite nicely. However, when he removed the hose, as the hydrogen burned at the top, air began to flow in the bottom. When there was a mixture of air and hydrogen, the mixture became explosive.
The second demo was Mr. Gaar's magnificent perpetual motion machine. This time he placed the apparatus on the front table and explained how it worked. He had obtained two gallon metal cans that had held duplicator fluid (older readers will recall mimeograph technology). One was placed on a ring stand, with its bottom a foot or so above the top of the other can, which was placed on the table. Each can had a two-hole stopper. A length of clear tubing lead from the stopper of one can to the stopper of the other.
The other connection to the top can was a short length of tubing whose other end was suspended over a funnel that drained into the lower can. A pinchcock was attached to this tube.
Mr. Gaar removed the pinchcock and a red, viscous fluid began running out of the end of that tube, dripping into the funnel. He explained that he his invention was not only a perpetual motion machine, it would actually generate free energy.
As the fluid ran into the funnel, he elaborated on how you could place the sending unit in the top of a five-story apartment complex, place the receiving unit in the basement, and generate enough electricity to light the building.
Even then, at age thirteen, I knew he was lying.
After a few minutes of his spiel, he re-attached the pinchcock, cutting off the flow, and moved the apparatus to a side table.
As soon as his back was turned, I went over and took the pinchcock back off, and the fluid started running again.
Eventually he noticed. “All right, who left the perpetual motion machine running?”
“If it was really a perpetual motion machine,” I spoke up, “it wouldn't matter if you left it running!”
I think this may have been a test. Mr. Gaar was good at making us think.