[IamIan]

Originally Posted by t vago

That's right.

Ok ... maybe it's just me being a bit thick or slow on the uptake ... but that seems like a VERY bold claim to me ... so here is the information ... show me your stuff ... you have a container of water and air at 80C what if any is the expansion ratio for the steam if any? ... Because you claim that this temperature information is the only information you need ... I can do anything else I can think of and not have to tell you any bit of the rest of the context details ... and no matter what I do it should have no influence at all on the expansion ratio ... as if there can only ever be one specific expansion ratio for one temperature.

So go ahead ... give me your one specific expansion ratio for this temperature ... the one specific expansion ratio that will hold the same for any and all other context details.

My prediction ... you'll back away from your very bold claim above in some way ... but maybe I'm wrong ... you tell me.

Originally Posted by t vago

1. You're quibbling about the ideal gas law. While it is true that no gas perfectly behaves as an ideal gas, the ideal gas law is sufficient for most gases. Not saturated steam, and not for steam in various regions of temperature and pressure.

I don't think I'm quibbling about the ideal gas law ... it shows the relationship clearly ... but the point I was making you've already agreed to ... different volume containers will have different pressures for the same 0.96g of liquid water +0.04g of steam ... if you prefer to come to agreement of that same point from some other direction ... I don't see much significance in what path you took to get there.

potato 'pohtahto' kind of thing to me.

Originally Posted by t vago

2. You're flat-out wrong about using "since no gas exactly follows the ideal gas law, we can still treat steam as an ideal gas."

While your wording would seem to infer that you are quoting me here ... I don't recall ever writing this ... and it doesn't read like something I would write... I don't ever recall writing this which you seem to here be claiming is a quote from me.

So do me a favor ... remind me of which post of mine you got this quote from... maybe that will jog my memory or something.

Originally Posted by t vago

The red area shows where you can treat steam as an ideal gas. Note that for most of the saturation line between steam and liquid, there is no red.

I think I have a different point of view about the ideal gas law , than it seems to me that you do ...the ideal gas law is not the sum total of all influences ... it describes how ideal gasses would react ... the ideal gas law does not include all other factors of real world substances ... it does not include for example that at some temperature and pressure gasoline will auto-ignite , and that reaction will have significant effects on temperatures and pressures ... it also won't tell you what the flame speed of the reaction will be , or what the specific heats of the materials will be, or if they are exothermic or endothermic , etc... it isn't that the ideal gas law doesn't work for systems that have gasoline in the them ... it is not a universal theory of everything ... if the specific substances you have behave in certain ways some of that is not part of what the ideal gas law describes.

I'm sure if someone made a plot of gasoline and air at different temperatures and pressures ... like that graph of yours for water and steam at different temperatures and pressures ... that there would also be significant parts of the graph that also deviate greatly from what just the ideal gas law would predict without any other considerations of the substances.

Which is what I see that graph of yours showing ... to me , it is showing that if you only looked at the ideal gas law and ignored the other behaviors of the substances involved , you would at some temperatures and pressures get very different results than what just the ideal gas law alone would predict... and to me ... that is completely expected to me ... and in no way invalidates the principles of the ideal gas law itself ... it is not a theory of everything ... and I don't expect it to be.