01039 IUPAC Gold Book - chemical substance 10.1351/goldbook.C01039 C01039 current 1 Matter of constant composition best characterized by the entities (molecules, formula units, atoms) it is composed of. Physical properties such as density, refractive index, electric conductivity, melting point etc. characterize the chemical substance. electric conductivity https://goldbook.iupac.org//terms/view/E01926 melting https://goldbook.iupac.org//terms/view/M03821 refractive index https://goldbook.iupac.org//terms/view/R05240 Physical Chemistry Division, unpublished https://goldbook.iupac.org/terms/view/C01039/html https://goldbook.iupac.org/terms/view/C01039/json https://goldbook.iupac.org/terms/view/C01039/plain Citation: 'chemical substance' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.C01039 The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using. 2026-05-08T22:26:43+00:00