There are many examples of
YouTube videos of the reaction of potassium chlorate with various
candies. See this one using a candy
cane. Sugar counts as organic matter and this is
the result. http://www.youtube.com/watch?v=bbO-1C_BP_khttp://www.youtube.com/watch
?v=bbO-1C_BP_k YouTube
will give you links to other similar
videos. These are pretty violent
reactions. The organic starts the decomposition
of potassium chlorate to generate oxygen gas; hence the combustion and
inability to blow out the flame. The reaction is
generating its own oxygen and it is
exothermic. If you just have to
wow your high school students with this reaction make absolutely sure
you follow suggestions 3 & especially 4. The
shield is crucial. The metal base needs to be
heavy and the instructor should be wearing a face shield and heavy
gloves. If they elect to use the hood sash as
protection as in this video, opening the sash exposes nearby students to
considerable
hazard.
Flinn Scientific=92s catalog gives several
warnings for those who might purchase potassium chlorate, e.g. in part:
=93=85Because this substance is so frequently a source of accidents on
school premises we have elected to list some of the incompatible
substances which should be avoided=85..=94 and =93Molten
KClO3 is a powerful oxidizer of organic materials like
the rubber in the stoppers used in the generating
apparatus. Explosions can and do
result=85.=94
If
you actually want to demonstrate a chemical principle there is a much
safer way to carry out a decomposition reaction to generate oxygen and
relate it to the reaction stoichiometry or as a gas law
experiment. Add Baker=92s yeast to 3% hydrogen
peroxide solution at room temperature. The
hydrogen peroxide is the composition available in discount
stores. You can weigh before and after to get
the amount of oxygen produced and calculate the actual % hydrogen
peroxide. You can also displace water with the
oxygen generated and check gas laws. This is the
method we use at University of Wisconsin-La
Crosse. There are articles in the Journal of
Chemical Education about the hazards of the potassium chlorate method
(1982) and detailing the proposed alternative method to generate oxygen
(1988). We use a simpler apparatus than the one
in the article. Note the
dates. This is not a new
problem. Doing a hazardous reaction many times
without an accident does not prevent one from
happening.
Sandra Koster
Senior Lecturer
UW-La
Crosse
