Greetings all,
You've hit one of my pet peeve topics! I quit doing any pyrotechnic demos long ago for my classes or for college "outreach" activities. Yes, they are exciting - for all involved! However, my fear was that students/audience would attempt to do these demos at home (some did!) not fully understanding the hazards nor take the appropriate safety measures. So, a critical self-assessment of the purpose of the demos ensued. What was I trying to demonstrate? What message was I sending? I stopped doing them altogether. I could not do these activities with a clear conscious, not to mention the mixed messages.
To continue on my rant..... I cringe when I see "science demonstrators" on TV shows that do these pyrotechnics. Many times kids are doing the activity. The host has no idea what to expect. The result is almost always a "near miss." In addition these demos are large scale (let's make a mess!!). They might be visually attractive for a viewing audience, both live and broadcast, but they are just that - theater - potentially dangerous theater.
When people see a demonstrator do an "act" and/or blow stuff up, it is often interpreted as "real science." Little consideration is given to the chemistry involved or to the safety. Consequently, students enter into our chemistry programs, in both high schools and colleges, with a distorted understanding of what chemistry really is. Chemistry is at once an experimental/observational science and a quantitative science. Yes, Suzie and Johnnie, there's math! And, yes, you can be severely injured or even killed doing experiments if you do not follow appropriate safety precautions. No, we do not blow stuff up - and, hopefully, neither will you. I do agree that math is a deterrent to entering students, but it doesn't have to be!! (I'll refrain from another rant.)
What do I do now? Any "public" demo that I do is based on water. There are so many great activities that can capture the imagination as well as get the audience to think as a chemist might think. Yes, it is still theater, but it is theater with a purpose. I have fun with it. My message is that water is an incredible molecule that can open up the wonders of chemistry to those who will explore it. Why do things dissolve in water? How does it happen? Why does water expand when it freezes? Why does water have a higher bp than methane or H2S? Then there are bubbles - glorious bubbles! The list goes on and on.
If I want to do a demo in the classroom, I find that videos are just as effective. And, there are some very good ones out there! I can pause, make commentary, and replay. The point of a demo is to illustrate a concept, right? So, the only reason in my mind for a "live demo" is the WOW factor. But, now you have to deal with safety issues, prep and clean-up, waste disposal, etc. No thanks! (I don't have a graduate assistant to do that dirty work.)
A personal story - What got me interested in chemistry was my Dad - he was a physician who majored in chemistry as an undergrad. When I was about 10, I had a little rocket that was powered by vinegar and baking soda. (I also had a little boat with the same propulsion mechanism. Anybody else remember these or am I too old?) Getting the proper ratio of vinegar and baking soda to get the maximum CO2 production and maximum altitude was by trial and error - until Dad showed me the chemistry and the stoichiometry. (I didn't know that's what it was, but I also learned about limiting reagents in the process.) But I now had a reproduceable method of fueling my rocket or boat and the math to go along with it. I also learned about triangulation to determine the altitude. (Thanks, Boy Scouts!) Math with a purpose!
