vapor pressure
Low frequency (C1-C2). Specialized term.Technical / Scientific
Definition
Meaning
The pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system.
A measure of a substance's tendency to evaporate; higher vapor pressure indicates a greater tendency to become gaseous. In broader contexts, it can describe pressure in a volatile or unstable situation.
Linguistics
Semantic Notes
Primarily a fixed compound noun in chemistry and physics. The spelling 'vapour pressure' is standard in UK English. Conceptually central to understanding boiling points, distillation, and volatility.
Dialectal Variation
British vs American Usage
Differences
Spelling: 'vapour pressure' (UK) vs. 'vapor pressure' (US). Pronunciation of 'vapor/vapour' differs accordingly.
Connotations
None; purely technical.
Frequency
Equally common within the respective scientific registers of each variety.
Vocabulary
Collocations
Grammar
Valency Patterns
The vapor pressure of [SUBSTANCE] is [VALUE].[SUBSTANCE] has a high/low vapor pressure.Vapor pressure increases with temperature.Vocabulary
Synonyms
Strong
Neutral
Weak
Vocabulary
Antonyms
Phrases
Idioms & Phrases
- “[no idioms]”
Usage
Context Usage
Business
Rare. Possibly in specific industries like petrochemicals or pharmaceuticals when discussing product properties or safety.
Academic
Standard term in chemistry, physics, chemical engineering, materials science, and meteorology textbooks and research.
Everyday
Extremely rare. May appear in simplified explanations of weather (humidity) or cooking (pressure cookers).
Technical
The primary context. Used in lab reports, engineering specifications, safety data sheets (SDS), and process design.
Examples
By Part of Speech
verb
British English
- The liquid will vapourise, thus affecting the pressure in the system.
American English
- The solvent will vaporize, thus increasing the pressure.
adverb
British English
- The system behaved vapour-pressure-dependently.
American English
- It is a vapor-pressure-controlled process.
adjective
British English
- The vapour-pressure reading was critical.
American English
- The vapor-pressure data was recorded.
Examples
By CEFR Level
- Water boils when its vapor pressure equals the air pressure.
- Different liquids have different vapor pressures at room temperature.
- We calculated the vapor pressure of ethanol using the Clausius-Clapeyron equation.
- The abnormally high vapor pressure of the novel solvent necessitated a redesign of the containment vessel to prevent fugitive emissions.
Learning
Memory Aids
Mnemonic
Imagine steam (VAPOR) pushing up on the lid of a boiling kettle. The FORCE of that push is the VAPOR PRESSURE. More heat, more push.
Conceptual Metaphor
ESCAPE FORCE: The vapor pressure is the 'force' with which molecules try to escape the liquid. A STRUGGLE FOR FREEDOM between cohesive forces and kinetic energy.
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Do not translate as 'парное давление' (incorrect).
- Correct term is 'давление пара' (davleniye para).
- Beware of confusing 'pressure' with 'давление' (correct) and 'vapor' with 'пар' (correct), but keep the word order as in English for the compound term.
Common Mistakes
- Misspelling 'vapor/vapour'.
- Confusing it with atmospheric or gas pressure in an open system.
- Using 'vapour pressure' as a countable plural (*vapour pressures of water* is possible, but *a vapour pressure* is standard).
- Incorrect preposition: 'vapor pressure on temperature' instead of 'vapor pressure *of* a substance *at* a temperature'.
Practice
Quiz
What does a high vapor pressure at room temperature indicate about a substance?
FAQ
Frequently Asked Questions
No. Vapor pressure is the pressure exerted by a substance's own vapor in equilibrium. Atmospheric pressure is the pressure exerted by the air in the atmosphere.
No, in a closed system at equilibrium, vapor pressure depends only on temperature and the identity of the substance, not on the volume of liquid present.
They are inversely related. A substance with a high vapor pressure at a given temperature will have a low boiling point, as it more readily forms vapor.
It's crucial for understanding distillation, predicting weather (humidity), designing chemical processes, and assessing safety hazards (volatility of fuels).