Abstract
We present here general properties of thermodynamic processes where the pressure of an ideal gas has a linear dependence with its volume. We call these thermodynamic processes as “straight-line processes”. By integrating the function of gas pressure with its volume it was possible to write an expression of the work done by the gas in the straight-line processes in terms of the initial state of the gas and the rates of pressurization and expansion of the transformation. By applying the First Law of Thermodynamics and using the relation between the temperature and the internal energy of an ideal gas we obtain the general expressions of the internal energy variation and of the heat absorbed by an ideal gas after going through an straight-line process. The molar heat capacity associated with straight-line processes, as well as the entropy variation of the gases which suffer these transformations, could be written in terms of the expansion and pressurizing rates. The properties of the isobaric and isovolumetric processes can be identified as special cases of straight-line processes and recovered from the expressions obtained by considering the value of unity for the pressurizing and expansion rates respectively.
Keywords:
p-V diagrams; molar heat capacity; entropy; reversible processes
