Subject: Bunsen Burner Cool Zone (2)
I do the match experiment (i.e. the students do it) holding the match horizontally. They are even more astonished as they see the wood charring and the head unchanged. Of course, they have to withdraw the match in time, otherwise the head does ignite. An observant 10th grade student, Helen Malka, noticed that if you thrust a burning match into the center of the "cool" flame, the part of the match in the center stops burning. This is, of course, the same phenomenon, but is perhaps even more thought provoking.
Included are some variations on the experiment which I also do. We use portable burners, but the experiments can be done just as well using regular ones.
The students are always inquisitive to know what part the holes play in determining the flame color and heat. The drawing below illustrates a very simple way of showing that air is being drawn in (some students had thought that if the holes were opened, gas would come out). There is room for futher discussion here (apart from the Bernouilli effect per se), regarding the changing color of the flame. [Less air goes in, if the combustion products of the match take its place.]
I published a riddle relating to the Bunsen burner flame in Chem13 News (No. 291, p.4).
Menachem Begin High School, Safed, Israel