Points outside the vapor dome

You mentioned in office hours how the curve outside the vapor dome should be non-linear (line 2 --> 8 and 7-->1). But despite using as many points as we could (by inputting S values in the appropriate range in the program) we still get curves that appear to be very linear. How do we proceed?

Depending on which isobar you are at, it's not necessarily going to be a very pronounced curve, but it definitely shouldn't be exactly a straight line either. If you are using the thermodynamic software correctly then it shouldn't lead you astray...you can always look up examples in a textbook or online if you are curious exactly how much of a curvature there should be to the isobars (it might not be as much as you are thinking there should be).