Triple point

Definition

The triple point is the unique set of conditions at which all three phases (solid, liquid, and gas) of a substance coexist in thermodynamic equilibrium. It is specific to each substance and occurs at a precise temperature and pressure.

5 Must Know Facts For Your Next Test

1. The triple point represents the only set of conditions where solid, liquid, and vapor phases can coexist simultaneously.
2. For water, the triple point occurs at exactly 0.01°C and 611.657 pascals.
3. It serves as a standard fixed point in the definition of the Kelvin temperature scale.
4. The concept of a triple point is crucial for understanding phase diagrams and phase transitions.
5. Triple points are used in calibrating thermometers due to their precise and reproducible properties.

Review Questions

• What are the temperature and pressure conditions for the triple point of water?
• Why is the triple point important for defining temperature scales?
• How does the triple point appear on a phase diagram?

Related terms

Phase Diagram: A graphical representation showing the equilibrium between different phases of a substance as a function of temperature and pressure.

Critical Point: The end point of a phase equilibrium curve, beyond which distinct liquid and gas phases do not exist.

Equilibrium: \text{A state where there are no net changes in the quantities of reactants or products; in this context, it refers to phase equilibrium among solid, liquid, and gas phases.}