tst EN ISO 80000-9

TS EN ISO 80000-9 is a terminology and units standard for quantities used in physical chemistry and molecular physics. It sets out how these quantities should be named, symbolized, and defined, helping reduce ambiguity when the same concept is described differently across textbooks, papers, and technical documents.

A common language for physical chemistry and molecular physics

Physical chemistry deals with the quantitative description of chemical systems, including thermodynamics, equilibrium, solutions, phase behavior, and related properties. Molecular physics focuses on matter at the atomic and molecular scale, where structure, interactions, and motion shape observable behavior. In these fields, quantities may cover topics such as energy, temperature, amount of substance, pressure, concentration, chemical potential, and molecular properties. The value of this standard lies in defining consistent names and symbols for that vocabulary.

What this part contributes

• Provides common names, symbols, and definitions for relevant quantities and units.
• Includes conversion factors where appropriate.
• Aligns physical chemistry and molecular physics terminology with the wider ISO 80000 series.
• Helps reduce interpretation differences caused by inconsistent notation and unit usage.

This document is primarily about standardizing scientific language rather than prescribing a laboratory method or equipment specification. Its practical benefit is in reporting, notation, and technical communication, where precise and consistent symbols make equations and measured values easier to interpret.

Together with the referenced ISO 80000-3, -4, and -5 parts, it forms part of a broader coherent framework for quantities and units in the physical sciences. That makes it easier to read and compare technical information in physical chemistry and molecular physics contexts.