The Art of the Chemical Demonstration

demonstrations

One of my favorite things to talk about with my colleagues is the use of lecture demonstrations in teaching. There seems to be a push in my district to stop using chemicals whenever possible and get to computer simulations and video in place of wet chemistry. I don’t think they are thrilled with me since I can’t envision ever taking the chemistry out of chemistry.

I often like to finish off a chapter or unit with an hour long demonstration based review lecture. This allows me to engage the students in a meaningful conversation about the material that they are about to be tested on. Since it is the end of the unit I often ask them to tell me what is going on in a demonstration and how it is relevant to the material we are covering rather than me explaining it. One technique I learned while working at the Institute for Chemical Education at UW-Madison was to have a student pretend to be a radio sportscaster and describe what they are seeing and even have a second student join them to provide some “color” commentary about the demonstration.

Having kids describe demonstrations has shown me how often a student’s mind goes in directions I had never anticipated. This is sometimes a good thing, but mostly bad. So having an opportunity to take a day and make them describe to me on the spot what they “see” in a chemical reaction is an excellent technique to open the lines of communication. I am hoping over a series of several of these posts to describe the demonstrations I am using and what I am trying to get out of them. It has pushed me to have some real soul searching discussions with my fellow chemistry teachers at my school to evaluate why we are doing certain demonstrations, labs, and lessons.

My first thought with these posts is to revisit the six characteristics of an effective demonstration from the Shakhashiri books. They are:

1) Demonstrations must be timely and appropriate.

I have had a colleague that went to every workshop they could find and came back and just did whatever they saw at the workshop the previous weekend. The kids liked the class but when AP Test time came around they were the only teacher on campus to have straight scores of 1. The students learned little abut the material and had no take home understanding of the subject matter.

2) Demonstrations must be well prepared and rehearsed.

If you don’t know how it works and what is going to happen, everyone is in danger. A different colleague of mine once tried doing an iodine clock demonstration where you pour 200 mL of solution A into a large beaker with 200 mL of solution B. The problem was he poured the large beaker into the small beaker. Imagine the mess that he made.

3) Demonstrations must be visible and appropriately scaled.

A different colleague from many years ago used to turn his back to the students and hold beakers in his hand and write equations on the board describing what the students could not see. Not much learning there. Sadly this teacher was also seriously injured years later when performing a demonstration without proper safety protocols.

4) Demonstrations must be simple and uncluttered.

One of the teachers I went through teacher training with refused to decorate his bulletin boards because he said he wanted to be the most interesting thing in the room. Keep the kids attention on himself he said. Well this might be an over statement of the idea but we do need to keep our students focused on what is important about a demonstration.

5) Demonstrations must be direct and lively.

Remember the science teacher from the show “The Wonder Years”? He was played by Ben Stein. He could put a room to sleep faster then a pound of Ambien.

6) Demonstrations must be dramatic and striking.

Just hopefully not striking the kids or instructor.

So keep tuning in for a few more posts about chemical demonstrations.

 

Shakhashiri, Bassam Z. Chemical Demonstrations: A guide book for teachers of chemistry, Volume 1-5, University of Wisconsin Press, 1983-2011