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An RC Car That Runs On Soda Can Rings
polyp2000 writes with an Engadget excerpt to inspire instant toy envy: "A pair of Spanish engineers have recently unveiled the dAlH2Orean (see what they did there?), a R/C car that runs on aluminum. Dropping a few soda can tabs into a tank of sodium hydroxide produces enough hydrogen to power the little speedster for 40 minutes — at almost 20mph."
Hehe, this gives me the opportunity to pass along an old favorite to a much younger generation. We were doing this around the time that today's college students were being born. The best part is that you can still get all the pieces for this (unlike many stories 20 years before my youth, which centered around things like large gunpowder fireworks and F-size model rocket engines).
If you were to take a square of aluminum foil, fold it diagonally in half to create a crease, fill the crease with lye (available as Red Devil drain cleaner, among others), and the roll the whole thing up like a... uh... hand-rolled cigarette, and then to fill a (preferably small, 500 mL or less) bottle with a fair amount of water, into which you then place the Drano Reefer before quickly (but firmly) closing the cap and throwing it far, far away, you'd get the Drano Reefer bomb.
The hydrogen comes from the water; the NaOH is merely a catalyst preventing the 2Al + 6H2O -> 2Al(OH)3 + 3H2 reaction from getting stopped by aluminum oxide films, etc. Done right, the gas pressure will rupture the bottle, while the hydrogen produced will add to any flame. For obvious reasons, not recommended for glass bottles.
For an encore, take a metal can (soup, tomato, soda, whatever) and add roughly 1:1 ratio by volume of brake fluid and pool chlorinator (the "shock treatment" is preferred for its high free chlorine content). Adding fluid to chlorinator produces a delayed reaction; adding chlorinator to fluid produces a much faster reaction. Work with the proportions to produce the desired effect - if done properly, you can reliably produce any effect from smoke-only to rapid bonfire. Once you're comfortable with that, you can start working with paper or styrofoam cups to produce a self-immolating container.