Institute of Technology
learn phenomenologically some of the factors which affect the rates of
Experiment A: 50 mL (circa 2 ounces) of 3% hydrogen peroxide, one
activated dry yeast, two quart kitchen storage bags (with ties), small
jar with cap, matches, fireproof surface, and a cigarette or wood
experiment B: two tablespoons household flour, fireproof surface (e.g.
food can), funnel with three foot rubber or plastic tube attached,
(preferably long “fireplace” type)
bag 1 with air and tie off. To bag 2 add yeast and capped jar
containing hydrogen peroxide, force out most of the air, and tie off,
then remove cap from bottle and allow contents to mix. Bag will slowly
inflate as an enzyme in the yeast acts as a CATALYST for the
decomposition of hydrogen peroxide into water and oxygen gas. Place
bags on fireproof surface and touch each with glowing cigarette or
splint. With bag 1, a small hole will be formed when the plastic melts
but bag 2 will burst into flame, demonstrating the effect of reactant
CONCENTRATION on reaction rates. (Bag 1 contains 20% oxygen by volume
and bag 2 nearly 100%. Can be related to signs in hospitals where
oxygen is being administered to avoid sources of ignition.
[P.S. Using two yeast/ peroxide bags, cooling one with
ice and warming the other –not too hot unless you also want to show
deactivation of enzymes – might be a way to demonstrate the effect of
TEMPERATURE on reaction rates from the rates of inflation of the bags.
Author hasn’t tried this yet]
tablespoon of flour on inverted can and try to ignite with a match;
will get some charring but not extended flame. Place another tablespoon
of flour in wide end of funnel, lift above your head, and hold a
lighted match about a foot above the funnel while blowing into tube.
With some practice, a large flame of burning flour will form (more
impressive if room is darkened first) showing the effect of SURFACE
AREA on reactions involving solids or gases. Can be related to
explosions in grain elevators, using twigs to start campfires.
Describe other situations involving the above
and ask students to predict effect on the reaction rate. Extra credit
for students coming up with their own examples.
This experiment provides a phenomenological way
demonstrate factors that affect the rates of chemical reaction with