Learned about sodium in 11th grade Chemistry class. There was a big chunk of sodium in a jar of oil in the Lab store room, and the teacher loved to show it off. This was one of those carbon-copy back East schools, all brick, big arched entryway, 11ft ceilings etc. The had put a single story addition on the back side for a cafeteria, and the Lab windows opened onto the flat roof of the cafeteria. Prof cuts off a pretty good chunk of the sodium, and it had rained the day before and there was a big puddle on the roof below. He tossed the sodium in the puddle (11AM) and KABOOM!!! Vaporized the puddle, rattled all the windows, and all the matronly cafeteria ladies in white ran screaming out the back door. Teacher had to go to the Principal's Office! My gramps was Prez of the School Board, and got ass-chewing calls that night from ALL the ladies- small town, and he knew all their farmer hubbies. He tried really, really hard to not laugh when I told him what happened...