The familiar phases of matter are solid, liquid, and gas—which for water amounts to ice, water, and steam. Atoms are arranged differently in each of the phases, with solid ice the most structured and gaseous vapor the most random. When a phase transition converts liquid into gas—as happens when water boils, for example—or solid into liquid—as occurs when ice cubes melt—the material stays the same since all the same atoms and molecules are present.
