A3. Additive Quantities

Appendix A3 315

A3 Additive Quantities¶

Quantities in thermodynamics can be classified into the following categories:

• A quantity is additive or extensive if its value depends on the size of the system. For example, if an object is split into two parts, its mass and volume (additive quantities) are also split. The additive quantities used in this book are $E, H, m, S, U$, and $V$ (see the list of symbols on page 328).

• A quantity is non-additive or intensive if its value does not depend on the size of the system. For example, if an object is split into two parts, its temperature remains unchanged. Specific (or mass-related) quantities are all non-additive. The non-additive quantities used in this book are $C, c, e, h, p, s, T, u, v, x, z, \gamma$, and $\rho$ (see the list of symbols on page 328).

• Some quantities are neither additive nor non-additive; so is, for example, the area of the surface surrounding a system.