2
Aspects of Thermodynamics
Chemical thermodynamics can provide the food scientist with important
quantitative knowledge. It treats—despite its name—equilibrium situations.
Three components ofthermodynamic equilibriumcan be distinguished: (a)
mechanical, implying that there are no unbalanced forces; (b) thermal, i.e.,
no temperature gradients; and (c) chemical, implying that no chemical
reactions and no net transport of components occur. Thermodynamics may
tell us whether there is equilibrium and, if not, in what direction the change
will be, but nothing about the rate at which any reaction or other change
may occur.
Thermodynamic theory does not involve molecular explanations and
is thus model independent. Nevertheless, and even because of this, it is very
useful because it is rigorous. In other words, it is always correct, provided,
of course, that it is applied in a correct manner. Physical chemists mostly
combine thermodynamic concepts with molecular theories and have thus
developed powerful tools for studying matter.
Some of the theory will be briefly recalled in this chapter, and
applications to foods will be illustrated. It is by no means an attempt to treat
the rudiments of thermodynamics: the reader is advised to study a general
textbook.