Reactive Alkali Metals

Alternate titles:

Reactive Metals

To demonstrate reactivity of alkali metals in contact with water.

Any alkali metal reacting with water is extremely exothermic, and care must be taken when performing this demonstration with mass of metal and water reacted.
Wear approved safety goggles and gloves.

Minimize the amount of air exposure of metals by preparing this only a few minutes prior to the start of the demo. Water molecules in the air might start the reaction.
Pour a bit of mineral oil into the petri dish.
Clean tweezers and knife with DI H₂O, dry well, then dip in mineral oil to prevent any contaminants from starting a reaction.
Use the oiled knife to cut small pieces of the requested metal and place them on the oiled petri dish.

Fill beaker(s) with DI H₂O and place a sheet of filter paper on top of the water so that it floats.
Carefully drop the metal pieces onto the filter paper.
1. The purpose of the filter paper is to slow down the reaction by slowing down the hydration of the metal molecules and the removal of the coating of mineral oil.
2. This slow reaction will also allow the metals to burn their respective colors, similar to flame tests.
The reaction of pure alkali metals with water makes their respective hydroxides.
1. Demonstrate this by adding phenolphthalein.

After the reactions are complete, test the pH of the remaining solution. If the pH is greater than 8, neutralize it with sodium bicarbonate before pouring down the drain.
Any unused metals go back into their storage container under mineral oil in the appropriate storage cabinet.

This demo adapted from the demo library of the Chemistry department at the University of Illinois at Urbana-Champaign.