The secret of the Cola can: what is it hiding?

What secret is an ordinary aluminum soda can hiding?

Safe­ty pre­cau­tions

Wear pro­tec­tive gloves, glass­es, and a mask. Work in a well-ven­ti­lat­ed area. Per­form this ex­per­i­ment un­der adult su­per­vi­sion only!

Reagents and equip­ment

  • soft drink in an alu­minum can;
  • sand­pa­per;
  • beaker;
  • drain clean­er;
  • wood­en rod;
  • glass con­tain­er.

Step-by-step in­struc­tions

Buff the top lay­er of paint off of an alu­minum can. Open the can and use a wood­en rod to sus­pend it in a suit­ably-sized beaker. Add some drain clean­er (usu­al­ly a 10% sodi­um or potas­si­um hy­drox­ide so­lu­tion). Ob­serve a tu­mul­tuous re­ac­tion and re­lease of gas. Wait two hours. Take the can out of the liq­uid. It would seem that the alu­minum has com­plete­ly dis­solved, but the drink hasn't leaked out!

Process de­scrip­tion

This or­di­nary alu­minum can is con­ceal­ing a de­vi­ous se­cret – it is cov­ered with a pro­tec­tive lay­er not only on the out­side, but on the in­side as well! When we re­move its paint coat­ing, we ex­pose the alu­minum, which eas­i­ly re­acts with a drain clean­er that con­tains an al­ka­line com­po­nent. But even when the alu­minum has dis­solved com­plete­ly, the drink will not leak out. There is a sec­ond ma­te­ri­al in­side the can – a lay­er of plas­tic that keeps the drink it­self from in­ter­act­ing with the alu­minum.

2Al + 2NaOH + 6H₂O = 2Na[Al(OH)₄] + 3H₂