Consider steam. Plot the 500-K isotherm in P–v space using the NIST online database as your data source. Also plot on the same graph the 500-K isotherm assuming ideal-gas behavior. Start (actually, end) the isotherm at the saturated vapor line. Use a sufficiently large range of pressures that the real isotherm approaches the fictitious ideal-gas isotherm at large specific volumes. Use spreadsheet software for your calculations and plot.