Estimating the Pressure Required to "Pop" a Film Canister Popper

Featuring contributions from Paul Lee and John Tian.

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: 

1. 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.
2. 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.
3. After the glue has cooled, attach the syringe to the needle using the Luer lock.
4. Carefully place the cap on the film canister without bending or twisting the needle in the canister. 

Demonstration:

1. Remove the cap from the canister.
2. Pull the syringe back to 60 mL.
3. Carefully place the cap back on the canister.
4. Aim the apparatus at a target away from people (e.g. the ceiling).
5. Pop the film canister cap by rapidly pushing in the syringe plunger as far as it goes.
6. If the "pop" does not work, go back to step 1.
7. 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.

A Vinegar/Baking Soda Baster Blaster

Featuring contributions from Giuliana Bailey, Paul Lee, John Tian

The reaction of baking soda and vinegar is a familiar one for many science students; the formation of carbon dioxide gas as a byproduct is often used to create a “volcano” or “rocket” effect. This demonstration uses the buildup of pressure from the formation of the carbon dioxide gas in a water bottle to propel a turkey baster into the air. The baster tube should have a round cross-section in order to effectively fit the bottle opening, and we recommend that the rubber bulb be fastened to the tube with electrical tape.  To perform the demonstration, add about 16 g of baking soda to an empty 500 mL water bottle.  It is not necessary to clear the baking soda powder away from the hole in the bottle  Use the baster to draw up about 40 mL of vinegar.  Quickly place the point of the baster with vinegar into the bottle with baking soda.  The baster tip should seal into the bottle but not fit so tightly that the baster cannot move.  Squeeze the vinegar into the bottle, and, making sure that the bottle and baster are still standing upright, release your grip on the baster bulb.  Within seconds, the carbon dioxide produced by the reaction will propel the baster into the air.

Sorry, some sort of error is turning my pictures sideways!

Seltzer Popper Launches Glow Stick

I discussed in previous blog entries how pressure from chemical production of carbon dioxide can be used as the basis for propulsion. The carbon dioxide can be produced by reaction between acids and carbonate salts. The picture below shows a rocket based on the popular demonstration involving water and AlkaSeltzer® in a 35 mm film canister placed on a chassis made from LEGO® parts. The "fuel" for the popping canister demonstration is approximately half an AlkaSeltzer® tablet, which is placed into a 35 mm film canister (Fuji-brand film canisters seem to work best). Water is added to the canister (to fill it approximately one third to one half full) and then the canister is capped. Ordinarily, in demonstrating these sorts of poppers the canister is placed upright, but in this case the canister is placed upside down and a bit of poster putty is used to hold a glow stick upright on the canister.  The force of the popper explosion is sufficient to launch the glow stick a few feet into the air. ABOVE: The glowing popper rocket assembly. BELOW: Launch of a blue glow stick popper rocket.  The orange glow stick popper rocket has not launched.

Igniting an LED-containing Balloon

I purchased a few LED-light containing balloons last night at Wal-Mart to fill with hydrogen and explode.  The thought is that the LED light would make the balloon out of the ordinary, maybe producing a line like "Hmmm...this balloon seems to have a warning light in it..."  I turned on the light in one of the balloons (it was dimmer than I would have liked) and filled it with hydrogen gas.  Tonight after dark I set it off with a candle on my back porch - still shots from a movie are shown below.

The LED light was tossed a couple feet but otherwise seemed unharmed - I opened it up and put a piece of plastic between the batteries to try to reuse later.  The balloon explosion seemed to have a few more sparks than usual - not sure why.  I'm also not sure what a more intense hydrogen-oxygen explosion would do to the LED and the batteries.

Bad Elements on Notebook Cover

A friend (Brittany Trang) found this notebook cover.  Seems like the goal is to make science somewhat appealing to girls (which is good) but the elements symbols are messed up (which is bad).  It's even sadder to think that it could have been done using boron (B), radium (Ra), indium (In), and yttrium (Y).