Ionization of Alkali Metals

Materials

3 Crystalizing Dishes with glass cover plates

Bottle of DI water

Lithium, Sodium and Potassium Metals

Plastic Forceps

Bottle of Soap Solution

Bottle of Phenolphthalein

Gloves and Goggles

Procedure

Place a recrystallizing dish on an overhead projector.  Pour water in the dish and add a squirt of phenolphthalein and a squirt of soapy water so the metals do not stick to the glass, and swirl until mixed.  Using tweezers, place a small piece of Lithium metal in the dish and cover with the glass plate. The Lithium will react slowly with the water turning the nearby water pink.

Repeat in another petri dish with Sodium and a third time with Potassium to show how reactivity of alkali metals increase down the periodic table.  The Sodium metal will skim over the surfce of the water leaving a pink trail. The Potassium will burn quickly, and can pop and jump around. Make sure to use the glass plate with the potassium since it can jump around quite a bit. Dim the lights to show potassium aflame on the water's surface.

Reactions

Li (s) --> Li⁺ (aq) + e^-

Na (s) --> Na⁺ (aq) + e^-

K (s) --> K⁺ (aq) + e^-

2. Water is reduced:

2H₂O (l) + 2e^- -> H₂ (g) + 2OH^- (aq)

Waste Management

The solutions can be neutralized and poured down the sink.