Response to a Change in T, P, or

In this and the next section we consider how properties in closed systems respond to changes in measurable state functions. Each such response is given by a partial derivative, and we are particularly interested in how conceptual respond to changes in measurables because several of those derivatives are measurable, even though the conceptuals themselves are not. 

We can consider any property (a state function) to be expressible as some function of temperature and pressure. 

Here F could be any of the extensive properties V, U, FI, S, A, or G. Then the total differential of F gives rise to two partial derivatives. 

With these four kinds of partial derivatives and many dependent properties to consider, a huge number of partial derivatives can be formed. Fortunately, only a few have simple and useful forms we are not interested here in the complicated or rarely used ones. We judge the importance of derivatives based on whether the dependent, independent, and held-fixed variables are conceptuals or measurables. Our classification scheme is summarized in Table 3.1. 

In this section we present those class 1 and class 11 derivatives that show how properties respond to changes in temperature. First, we consider the effects of temperature changes on two measurables— pressure and volume then we describe the effects on internal energy, enthalpy, and entropy and finally, we present the effects on Gibbs and Helmholtz energies. 

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