The hydrogen-air explosion in a Pringles can is by now "an old favourite".
Set up for collection of hydrogen
For those of us who don't have access to a hydrogen cylinder, the most convenient way to produce the gas is by the reaction between zinc and concentrated hydrochloric acid.
The problem is: how to fill the Pringles can with hydrogen and be sure that there is no air left — otherwise the demonstration may be very brief and possibly painful!
A simple solution is to take a length of glass tubing (about 25 cm long, internal diameter at least 4 mm) to which are affixed rubber stoppers at each end. One stopper fits the neck of the reaction flask, while a party balloon is fitted over the other one (above, not to scale).
The balloon is inflated until its volume is a little over that of the Pringles box. The neck of the balloon is pinched closed and the tube with the balloon detached from the flask. The balloon and tube are inverted, the tube is inserted into the Pringles box and the hydrogen released.
Using balloon to fill up Pringles® can
Because the tube reaches to the very end of the box, the hydrogen completely displaces the air.
What I find particularly handy about this setup is that if either the acid or the zinc needs "topping up", this can be done very simply by pinching the balloon closed, removing the tube from the flask, adding whatever is needed and replacing the tube, with no loss of hydrogen.
Extra tips:
- Pure zinc hardly reacts; add a little CuSO4(aq) to the flask.
- Dilute the conc. HCl with a little water to slow down the reaction.
- Remember to fire polish the ends of the tubing.
- Insert the tubing using a cork-borer. Flinn Scientific has both written and video instructions.1
Editor’s note: For those unfamiliar with this demonstration, you can watch Bob Becker perform this demo in a three-minute video2 posted on Flinn Scientific YouTube Channel, “Pringles Can Rocket in a Morning of Chemistry 2013”. It is fun to watch Bob present. He attributes this demo to “Irwin Talesnick, workshop presenter extraordinaire” from Canada. (We, Canadians always appreciate a shout-out.)
In the video description, Flinn includes a short explanation of the Pringles Rocket: “An empty Pringles potato chip can is filled with hydrogen gas and ignited. The hydrogen burns with a yellow flame for about one minute. As the air mixes with the hydrogen the flame will become smaller and smaller. Just before the mixture explodes a slight whistling can be heard. When the mixture explodes the plastic lid on the bottom will fly off and the can will shoot about 10 feet in the air.”
Flinn also states that this demo is intended for and should only be performed by certified science instructors in a safe laboratory/classroom setting. Flinn has posted a full write-up of this demonstration.3
References
- www.flinnsci.ca/how-to-insert-glass-tubing-into-a-rubber-stopper/vht0003/ and demonstrated here:
- Pringles Rocket, Flinn Scientific, Inc. ChemFax www.flinnsci.com/api/library/Download/f5274c2a1f2c4a0ab86c8f99d16dcd15
