6.13

# Summary of Week 6

This final week, you examined at the power of property relations in deriving various property changes upon other parameter changes.

Thermodynamic properties such as temperature, pressure, volume and entropy are related with each other. While some property changes depending on other property changes are kind of clear and can be easily obtained, other relations are not that intuitive. The power of property relations is to convert those non-simple relations into more familiar ones with some mathematical manipulation.

With the help of the property relation, the dependence of entropy on pressure can be expressed with more familiar form: the temperature dependence of volume. Property relations also proved one of the property of ideal gases, that the internal energy and enthalpy depend only on temperature.

Heat capacity does not change with pressure in most cases, however, heat capacity strongly depends on pressure sometimes. Through mathematical manipulation and a property relation, the variation of heat capacity with pressure is estimated.

The entropy change of mixing is equivalent to the change of entropy upon volume expansion of the constituent gases. The property relations effectively applied to derive the entropy change with volume changes, deriving the expressions of entropy of ideal mixing.