Black Snake Demonstration Idea
Another fun activity to do as a demonstration in class (although not at home) (also it may require a fume hood) is to take a Coke can and put it in concentrated sulfuric acid. This acid dissolves the aluminum can fairly rapidly (and creates a lot of heat and smoke in the process). Interestingly, though, it does not dissolve the plastic liner, which is the only thing that remains after the acid digestion has been completed. This is interesting because the soda itself is usually acidic, and the fact that there is a plastic liner is what prevents the acid in the soda can from slowly dissolving the aluminum. This also works best if you scratch or sand the paint off a little, which provides more direct contact between the acid and the soda can. Also, not all kinds of soda cans work. Some kinds of soda cans are made of steel, and that is much more resistant to the acid degradation than aluminum is.
While we are on the topic of sulfuric acid, it turns out that if you mix sulfuric acid with table sugar, it undergoes a highly exothermic (heat-generating) reaction to form a large black “snake.” This is because the acid causes the water to escape from the sugar, and leaves behind a brittle network of carbon that resembles charcoal.
Read more about soda cans and sulfuric acid here: https://www.stevespanglerscience.com/lab/experiments/soda-can-corrosion/
And more about sulfuric acid and sugar “snakes” here:
Safety note: Concentrated sulfuric acid is dangerous. Do not use this unless you have proper safety equipment, lots of ventilation, and you are a trained scientific professional.