enthalpy: meaning, definition, pronunciation and examples
C2Highly technical, scientific, academic.
Quick answer
What does “enthalpy” mean?
A thermodynamic property of a system equal to the sum of its internal energy and the product of its pressure and volume (H = U + pV).
Audio
Pronunciation
Definition
Meaning and Definition
A thermodynamic property of a system equal to the sum of its internal energy and the product of its pressure and volume (H = U + pV).
In thermodynamics, enthalpy is a measure of the total heat content of a system. In a broader scientific context, it represents the maximum amount of non-expansion work that can be extracted from a closed system, or the energy transferred as heat during a constant-pressure process.
Dialectal Variation
British vs American Usage
Differences
No significant differences in usage, definition, or pronunciation between British and American English. Spelling is identical.
Connotations
None beyond its precise scientific meaning.
Frequency
Equally rare and specialised in both dialects, confined to technical fields.
Grammar
How to Use “enthalpy” in a Sentence
the enthalpy of [noun phrase] (e.g., the enthalpy of vaporisation)an enthalpy change for [noun phrase] (e.g., an enthalpy change for the reaction)[adjective] enthalpy (e.g., standard enthalpy)Vocabulary
Collocations
Examples
Examples of “enthalpy” in a Sentence
verb
British English
- [No verb form exists.]
American English
- [No verb form exists.]
adverb
British English
- [No standard adverb form. 'Enthalpically' is theoretically possible but extremely rare.]
American English
- [No standard adverb form.]
adjective
British English
- The enthalpic contribution was significant.
- We performed an enthalpic analysis.
American English
- The enthalpic contribution was significant.
- We ran an enthalpic analysis.
Usage
Meaning in Context
Business
Virtually never used.
Academic
Used extensively in thermodynamics, physical chemistry, chemical engineering, and physics lectures, textbooks, and research papers.
Everyday
Never used in everyday conversation.
Technical
The primary context. Used in scientific research, engineering design, process simulation, and technical reports to quantify energy changes.
Vocabulary
Synonyms of “enthalpy”
Vocabulary
Antonyms of “enthalpy”
Watch out
Common Mistakes When Using “enthalpy”
- Confusing enthalpy with entropy. (Enthalpy = heat/energy; Entropy = disorder/randomness).
- Pronouncing it as /enˈθælpi/ in contexts where /ˈɛnθəlpi/ is standard.
- Using it outside of a thermodynamic or energy-related context.
- Forgetting it is a state function independent of the path taken.
FAQ
Frequently Asked Questions
No. Enthalpy (H) is a property of a system. The change in enthalpy (ΔH) under constant pressure is equal to the heat (q) transferred.
Yes. The enthalpy change (ΔH) can be negative (exothermic process, releases heat) or positive (endothermic process, absorbs heat). The absolute enthalpy (H) is usually not negative relative to a defined zero.
Enthalpy is measured in energy units, most commonly joules (J) or kilojoules (kJ) in the SI system. Older texts may use calories (cal) or kilocalories (kcal).
Because many real-world processes (e.g., chemical reactions in open containers, steam turbines) occur at constant atmospheric pressure. The change in enthalpy (ΔH) directly gives the heat transferred under these common conditions.
A thermodynamic property of a system equal to the sum of its internal energy and the product of its pressure and volume (H = U + pV).
Enthalpy is usually highly technical, scientific, academic. in register.
Enthalpy: in British English it is pronounced /ˈɛnθəlpi/, and in American English it is pronounced /ˈɛnθəlpi/ or /ɛnˈθælpi/. Tap the audio buttons above to hear it.
Phrases
Idioms & Phrases
- “[None. The term is strictly technical.]”
Learning
Memory Aids
Mnemonic
Think of ENTHALPY as the ENergy THAt is ALways PotentiallY available in a system at constant pressure (from the Greek 'enthalpein', meaning 'to warm in').
Conceptual Metaphor
Often conceptualised as a 'heat bank account' or 'energy reservoir' of a system.
Practice
Quiz
What does a positive change in enthalpy (ΔH > 0) typically indicate about a chemical reaction?