Is aluminum amphoteric? A picture is worth 1 x 10^3 words

After I read Myra Hauben’s interesting piece in the February 2014 Chem 13 News (page 8), I duplicated the reaction of a paint-free — the paint was sanded off — soda can in 6 mol/L NaOH(aq), side-by-side with the reaction of another can in 6 mol/L HCl(aq). The results are similar — see adjacent photo. The can on the left reacted in acid, the one on the right in base. This attests to the acid and base resistance of the plastic liner, and to the fact that aluminum is amphoteric — it reacts with acids and with bases. The reactions had roughly similar rates. It took approximately one hour. You can see these reactions on the University of Nottingham’s Periodic Table of Videos website.

This demonstration is worth doing in your class — worth much more than 1 x 103 words.

Soda cans corroded to have translucent plastic middles.