Pure Substances in Single Phases

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. 

Two volume properties of a closed system are defined as follows  

The cubic expansion coefQdent is also called the coefficient of thermal expansion and the expansivity coefficient. Other symbols for the isothermal compressibility are ff and 

These definitions show that a is the fractional volume increase per unit temperaffire increase at constant pressure, and kt is the fractional volume decrease per unit pressure increase at constant temperature. Both quantities are intensive properties. Most substances have positive values of and all substances have positive values of kt, because a pressure increase at constant temperature requires a volume decrease. 

If an amount n of a substance is in a single phase, we can divide the numerator and denominator of the right sides of Eqs. 7.1.1 and 7.1.2 by n to obtain the alternative expres- 

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CHAPTER 7 PURE SUBSTANCES IN SINGLE PHASES 7.1 VOLUME Properties... 

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