Experiment
8: Alka Rockets - Teacher Page
Purpose | Background | Preparation | In Class | Wrap
Up | Extensions
| Purpose |
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To design a paper rocket propelled
by Alka-Seltzer and water to demonstrate
Newton's third law of motion.
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| Background |
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The paper rocket in this activity
is propelled according to the principle
stated in Isaac Newton's third law of
motion: "For every action there
is an opposite and equal reaction."
Gas pressure builds inside the film
canister due to the mixing of Alka-Seltzer
and water which releases carbon dioxide.
This action continues until enough pressure
builds to blow the canister apart from
its lid. The reaction is the launch
of the rocket.
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| Preparation |
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Review and prepare materials listed
on the student sheet. It is most important
to use film canisters with lids that
snap inside. Do not use lids that
close around the outside of the canister.
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| In Class |
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This is an outdoor activity. If gusty winds are a problem, then place a quarter
in the canister to keep the rocket from falling
over. Launching near a wall where a metric tape
has been hung or where meter sticks have been
stacked may make it easier to judge how high the
rocket goes. You should require students
to wear safety glasses during this experiment
as a general safety precaution. Everyone
should stand away from loaded rockets when they
are on the launch pad. It may take 15 to 20 seconds
to build up enough pressure to launch, so a loaded
rocket should not be approached prematurely. These rockets can shoot 5 meters or more into
the air. No sharp objects should be placed on
top of the nose cone or elsewhere on the rocket.
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| Wrap-Up |
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One way to record the results of different
"fuel" mixtures is to make a simple
graph of height vs. amount of water. Such a graph
gives a clear, visual record of the observations
and can be used as evidence to support interpretations.
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| Extensions |
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Design and launch a
rocket powered by two, three or more film canisters.
Design a two-stage rocket. In each case, the students
will need to work cooperatively to use the knowledge
they've gained to solve problems of fuel mixtures
and timing.
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