The secret of the Cola can: what is it hiding?
What secret is an ordinary aluminum soda can hiding?
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;
- drain cleaner;
- wooden rod;
- glass container.
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!
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