Paul Needham
Stockholm University
‘Water is H 2 O’ is naturally construed as an equivalence. What are the things to which the two predicates ‘is water’ and ‘is H 2 O’ apply? The equivalence presupposes that substance properties are distinguished from phase properties. A substance like water (H 2 O) exhibits various phases (solid, liquid, gas) under appropriate conditions, and a given (say liquid) phase may comprise several substances. What general features distinguish substance from phase properties? I tackle these questions on the basis of an interpretation of a theorem of thermodynamics known as Gibbs' phase rule which systematically relates these two kinds of feature of matter. The interpretation develops the idea that the things substance and phase predicates apply to are quantities of matter which sustain mereological relations and operations and exploits these mereological features in distinguishing the two kinds of property. Gibbs' phase rule is a macroscopic principle applicable for macroscopic intervals of time. Bringing intervals of time into the picture calls for a more detailed consideration of the relation between macroscopic equilibria and the corresponding dynamic equilibria at the microlevel and throws into question the simple idea that quantities can always be regarded as collections of molecules. The account provides some insight into how the continuous, macroscopic conception of matter (‘gunk’) is reconciled with the discrete microscopic conception and illuminates the interpretation of substances present in mixtures
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DOI 10.1093/bjps/axp047
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References found in this work BETA

Parthood and Identity Across Time.Judith Jarvis Thomson - 1983 - Journal of Philosophy 80 (4):201-220.
What is Water?Paul Needham - 2000 - Analysis 60 (1):13-21.

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Citations of this work BETA

Philosophy of Chemistry.Michael Weisberg, Paul Needham & Robin Hendry - 2011 - Stanford Encyclopedia of Philosophy.
Mixtures and Mass Terms.David Nicolas - forthcoming - Dialectica.
Entropy and Chemical Substance.Robin Findlay Hendry - 2010 - Philosophy of Science 77 (5):921-932.

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The Phase Rule and the Notion of Substance.Paul Needham - 2012 - In Henk W. de Regt, Stephan Hartmann & Samir Okasha (eds.), EPSA Philosophy of Science: Amsterdam 2009. Springer. pp. 253-62.


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