Ohhh - a chemistry pt to the engineer! Actually I've used that as a demo for Middle school students. Put zinc in a flask with HCl, and stick a test tube over the fizzing piece of zinc. Hold the tube inverted and then stick a match in it. It makes a tres cool 'pop' (the tube won't explode as long as it's open on one end). Then diagram the equation on the board. Tends to wake them up and get their attention.
And, of course, our great Dane is correct, the surface area is a critical factor. What you've got is an inbalance between the thermodynamics of the situation (can the Al tab be dissolved) and the kinetics (how long will it take?). A practical analogy of this is to take a glass of water outside and see how long it takes to evaporate. And take an identical glass of water and pour it on the ground (concrete or something that won't absorb water, that'd be cheating). Since the surface area is much greater, the kinetics are changed.
/ end chemistry lesson
It's Amino world without Chemists
And, of course, our great Dane is correct, the surface area is a critical factor. What you've got is an inbalance between the thermodynamics of the situation (can the Al tab be dissolved) and the kinetics (how long will it take?). A practical analogy of this is to take a glass of water outside and see how long it takes to evaporate. And take an identical glass of water and pour it on the ground (concrete or something that won't absorb water, that'd be cheating). Since the surface area is much greater, the kinetics are changed.
/ end chemistry lesson
It's Amino world without Chemists