On a summer day, a clear glass holds water with several ice cubes floating inside. The cubes appear as solid, translucent shapes amid the liquid. They create visible chill lines on the glass exterior and shift position when the glass moves.
This setup stays in a stable state as long as ice remains present and distinct.
The threshold occurs at the exact instant when the final ice cube fully dissolves, with no solid remnant left in the glass.
Before this point, the contents show separate phases: solid ice pieces alongside liquid water. Immediately after, only uniform liquid occupies the glass—no solid forms, no separate cold cores, just a single consistent body of water.
The glass has now crossed the line from a two-phase mix to a single liquid state.