In the phase transitions among the solid, liquid, and gaseous forms of water, we see a profound demonstration of how properties at the molecular scale dictate the behavior of the bulk material. As ice is heated beyond its melting point, new avenues for molecular motion become open to the energy being added. Upon entering the gas phase, the water molecules can explore new territory, unavailable to the liquid or solid. These transformations can be seen as a shifting balance between the forces that bind the molecules and the thermal energy that excites these motions--a window through thermodynamics on the intricate mechanisms that drive chemistry.