Boyle’s law states that the volume of a gas is inversely proportional to its pressure (assuming constant temperature and moles of gas). This demonstration uses this principle to create a powerful launch of a film canister top. NOTE: Wear eye protection and enlist adult supervision for this demonstration!
Materials:
- Luer-lock plastic syringe with at least 60 mL capacity
- film canisters used for Alks-Seltzer popper demonstrations (white Fuji film canisters work best, ours was measured to have a 39 mL capacity)
- Luer lock syringe needle (we used 12 gauge)
- hot glue and glue gun
Preparation:
- Poke a
small hole with the needle, preferably no wider than the diameter of the needle, in the bottom of
the film canister. Be careful not to poke yourself! Remove the needle, cut and discard the sharp end of the needle off with a wire cutter, and replace in the canister.
- Glue
the needle firmly in the place with hot glue gun. Make sure to glue both
the inside and the outside of the canister to keep the needle firmly in
place. Make sure not to plug the hole of the needle with glue.
- After the glue has cooled, attach
the syringe to the needle using the Luer lock.
- Carefully place the cap on the film canister without bending or twisting the needle in the canister.
Demonstration:
- Remove
the cap from the canister.
- Pull
the syringe back to 60 mL.
- Carefully place
the cap back on the canister.
- Aim
the apparatus at a target away from people (e.g. the ceiling).
- Pop the film canister cap by rapidly pushing in the syringe plunger as far as
it goes.
- If the "pop" does not work, go back to step 1.
- Retrieve cap.
The film canister
cap flies off the film canister because of the buildup in gas pressure during a
rapid decrease in volume. In our hands, 60 mL of air was added to a 39 mL canister to produce a powerful pop. Therefore, the pressure inside
the canister would have built up from about 1.0 atm to about 2.5 atm. Pictures of the apparatus are shown below.
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