A few years ago, we launched a weather balloon during our summer science camp. The balloon reached an altitude of 30 km (100,000 ft)! Among other things, this project ended up being a great way to teach campers about the gas laws and how atmospheric pressure decreases with altitude.
The “Elephant Toothpaste” experiment is a very popular, albeit messy chemistry demonstration. To carry out this experiment, place a 250 mL graduated cylinder on something that you wouldn’t mind getting messy.
Last year I came across a link on Twitter regarding an art installation by Roger Hiorns in England titled “Seizure.” Some of you may have seen it too – a condemned flat in London was essentially sealed off and filled with more than 75,000 L of supersaturated copper sulfate solution.