There is also the one where you use a bent wire to score the plastic liner on the inside of the can then put the acid in the can and swirl it around and pour it out. This leaves the can looking perfectly normal but makes it so you can easily rip the can perfectly in two to the amazement of your chemistry students.
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Also how we can have liquids in cardboard boxes. People are very confused by that.
TIL.
Fun fact cigarette filters are a form of plastic too
There is also the one where you use a bent wire to score the plastic liner on the inside of the can then put the acid in the can and swirl it around and pour it out. This leaves the can looking perfectly normal but makes it so you can easily rip the can perfectly in two to the amazement of your chemistry students.