Triple Point

The triple point is the specific temperature and pressure at which a substance can coexist in three states simultaneously: solid, liquid, and gas. For example, in water, the triple point occurs at about 0.01°C and 611.7 pascals. At this exact condition, ice, water, and vapor can all exist together in equilibrium, constantly transforming into each other. It’s a fundamental concept in thermodynamics that helps define the precise conditions needed for a substance to change states and is used as a key reference point for temperature calibration.