Vapor Pressure

Pressure of vapor in equilibrium with its condensed phase.

Short definition

Pressure of vapor in equilibrium with its condensed phase.

Full explanation

Vapor Pressure in the context of liquids solids phase changes: Pressure of vapor in equilibrium with its condensed phase. In practice this means relating macroscopic observation (mass, pressure, color), particle-level picture (atoms, electrons, ions moving and rearranging), and symbolic representation (formulas, equations, units). For Vapor Pressure, students connect the definition to linked lessons: do not just memorize the phrase — predict what changes when conditions change and check with dimensional analysis.

Notation and units

• Notation: P_vap
• Common units: SI or derived, temperature in kelvins when in gas/energy contexts.
• Symbolic hint: See related formula if applicable.

Example

Example for vapor pressure: In a worked problem where this term appears, substitute measured values with correct units and check that the dimensional result matches the intended quantity. For instance, calculating a vapor pressure often uses the form $n=m/M$ or $c=n/V$ or $PV=nRT$ with $T$ in kelvins — illustrating how vapor pressure leads to a numerically different but dimensionally correct result when units are handled.

Confused with

• Boiling Point — distinction: Vapor Pressure is pressure of vapor in equilibrium with its condensed phase. while Boiling Point has a different defining property. See cross-link in glossary.

Related resources

• Topic: liquids-solids-phase-changes
• Formula library — when a specific equation involves this term it is linked.
• Constants — if a constant is required, it is sourced and versioned (NIST 2022).

Sources

• NIST Physical Constants 2022 (nist-2022, CODATA 2022). Accessed 2026-08-21.

Last reviewed: 2026-08-21 — Review due: 2027-08-21 — Author: Chemistry Fundamentals Editorial Team — Reviewer: Editorial Review Board (transparent placeholder).

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