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Triple Point

Triple point: where solid, liquid, gas coexist; water: 273.16K, 611.7Pa
Quick Reference
Formula / NotationTriple point: where solid, liquid, gas coexist; water: 273.16K, 611.7Pa
Also Known AsTriple point temperature, three-phase equilibrium point

What is Triple Point?

The unique combination of temperature and pressure at which all three phases (solid, liquid, and gas) of a substance coexist in equilibrium. The triple point of water (273.16 K, 611.73 Pa) is a fundamental reference point for the Kelvin temperature scale.

Formula & Notation

Triple point: where solid, liquid, gas coexist; water: 273.16K, 611.7Pa

Other Names / Synonyms: Triple point temperature, three-phase equilibrium point

Properties & Characteristics

The triple point is the unique combination of temperature and pressure at which all three phases (solid, liquid, and gas) of a pure substance exist simultaneously in thermodynamic equilibrium. It is a fixed, reproducible point used as a thermometric reference. For water, the triple point is at 273.16 K (0.01°C) and 611.7 Pa. The triple point lies at the intersection of the solid-liquid, liquid-gas, and solid-gas equilibrium curves on a phase diagram.

Uses & Applications

The triple point of water was previously used to define the Kelvin temperature scale. Triple point cells are used as primary temperature standards in national metrology institutes. Triple point data helps determine phase boundaries and construct phase diagrams for industrial applications.

Safety Information

Triple point is a physical property concept with no direct safety hazard. However, controlling conditions near triple points is important in processes that require specific phase states.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Triple Point
Formula Triple point: where solid, liquid, gas coexist; water: 273.16K, 611.7Pa
Synonyms Triple point temperature, three-phase equilibrium point

Frequently Asked Questions

The unique combination of temperature and pressure at which all three phases (solid, liquid, and gas) of a substance coexist in equilibrium. The triple point of water (273.16 K, 611.73 Pa) is a fundamental reference point for the Kelvin temperature scale.

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