After a big lecture on resonance today in Chemistry 1A where we learned about how to make fertilizer (Ammonium Nitrate) explode (which was what Timothy McVeigh used in the 1995 Oklahoma City Bombings), how to coat chalkboards with an unstable substance so that professors writing on it will cause small explosions, and how the Sarin nerve gas works, Professor Nathan Lewis was on a roll and had a TA take everyone out for Group 1A elements dropping in water demonstrations! I swear that this doesn’t happen usually. The lectures are usually really formal and direct with no fun and games here.
Well, as you may know, when Group 1A elements (Lithium, Sodium, Potassium, Rubidium, etc.) come in contact with water, they have a large exothemic reaction (meaning that lots of energy is given off) where they bond with an OH- group liberating hydrogen in the process. Example:
2Li+ + 2H20 -> 2LiOH + H2
(H2 is the symbol for hydrogen gas)
The energy given off by that reaction ignites the hydrogen gas causing the “explosion”.
So one of the TAs threw in decent sized chunks of Lithium, Sodium, and Potassium. Unfortunately, they didn’t try any of the other elements:
The effect was actually a lot better than these pictures show it. I only captured the beginning of the reaction. Later on, lots of smoke was generated. This was what I always wanted to do in high school chemistry…