# Chapter 7: Pure Substances in Single Phases

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$$\newcommand{\C}{_{\text{C}}} % subscript C$$
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$$\newcommand{\mB}{_{\text{m},\text{B}}} % subscript m,B (m=molar)$$
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$$\newcommand{\el}{\subs{el}} % electrical$$
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This chapter applies concepts introduced in earlier chapters to the simplest kind of system, one consisting of a pure substance or a single component in a single phase. The system has three independent variables if it is open, and two if it is closed. Relations among various properties of a single phase are derived, including temperature, pressure, and volume. The important concepts of standard states and chemical potential are introduced.