Red trails are produced as the sodium travels across the dish. Can do lithium and potassium to demonstrate increasing reactivity. Procedure A flask containing a yellow solution of ammonium vanadate is poured into a flask containing zinc amalgam. With shaking, solution turns yellow to green to blue to purple. Vanadium can be reoxidized with cerium sulfate.
Colors project well in petri dishes on an overhead projector.
An analog meter with a 30-cm scale is connected through an amplifier to a pH meter and a glass electrode. The same large meter can be used as a voltmeter for electrochemistry and as a thermometer for thermochemistry demonstrations. The two voltmeter demos offered are potential differences between Zn, Cu and Pb, and using bologna as a salt bridge. Endo- and Exothermic Reactions Procedure Hot and cold packs are passed around the class. Students can note the temperature change.