Why does lithium turn pink in water?

The Reaction Between Lithium and Water

When you drop a piece of lithium into water, a fascinating chemical reaction takes place right before your eyes. First, any protective oil is wiped away, and the lithium wire is placed directly into the liquid. As soon as it makes contact, the metal begins to react with the water.

During this process, hydrogen gas and eventually steam are safely evolved, causing the reaction to fizz without igniting. Lithium hydroxide is produced as a byproduct, creating a strongly alkaline environment right underneath the moving metal.

If a pH indicator like phenolphthalein is present in the water, the solution immediately turns a striking pink color. This happens because phenolphthalein shifts from colorless to its characteristic basic color whenever the surrounding solution becomes alkaline.