There are a couple of household chemicals that you can mix together to produce a very unstable purple-yellow powder. Unstable because when this powder is disturbed, it produces a loud bang as it very quickly turns into a purple-yellow gas. (I wont specify details here, but I’m sure you can find out what those chemicals are on Google - the clue is ‘purple-yellow!).
Anyway, back when I was at school, a friend of mine found out about this very exciting formula and we decided to try it out. Taking over an empty classroom we mixed the two chemicals together on a sheet of paper and, sure enough, a purple-yellow powder formed. We weren’t entirely sure what to do next ... we wanted to enjoy a nice, loud purple-yellow bang but neither of us were too keen to be the one to set it off. Eventually, we found a long broom and, from a good distance, prodded the paper. Nothing happened. We prodded it a few more times, but still no bang. We’d been deceived, we thought - of course nothing as great as a readily available, exploding purple-yellow powder could really exist. We left the classroom with heavy hearts as another friend entered, early for his next class.
There was a very loud bang. The friend came running out of the classroom, disorientated from his temporary deafness, his face stained a very satisfying purple-yellow color. His face stayed that way for several days.
When people came to investigate the bang, our friend was kind enough not to turn us in and the incriminating piece of paper was easily disposed of.