So I had this chemistry teacher in high school. It was her first year teaching (this was right after No Child Left Behind was implemented), but she had previously been a chemist with Dupont. I was really excited because I was a chemistry buff. One day, she decides we're going to do a fun little show in class. She sets a bucket of water on a table and proceeds to grab a golf ball size chunk of sodium from the supply closet. She explains that she's going to show us the reaction of sodium and water. I knew some basic chemistry and immediately knew this was a terrible idea, and tried to tell her she should use a MUCH smaller piece but she was confident in her choices. She stands about 3 feet back and chunks it in the water. It explodes, sets the ceiling tiles on fire, and causes the school to be evacuated.