Phase Diagram Quiz

I’ve been dealing with alarmist chemistry flunkies since I started writing, so time to start educating them.

Assume equilibrium.

  1. What is the vapor pressure of water at the surface of a lake at 0C?
  2. What phases of water exist at the surface of a lake at 0C?
  3. What is the vapor pressure of water at the surface of a lake at -20C?
  4. What phases of water exist at the surface of a lake at -20C?
  5. What is the vapor pressure of water at the surface of a lake at 20C?
  6. What phases of water exist at the surface of a lake at 20C?
  7. At what temperature do we find all three phases of water?

About stevengoddard

Just having fun
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25 Responses to Phase Diagram Quiz

  1. Andy WeissDC says:

    Duh! I don’t know teach. Could you gimme a hint?

  2. Grumpy Grampy ;) says:

    Lowes did not have a “Vapor Pressure Gauge” the last time I looked and neither did the co-op so I have no way to test the theory. 😉

  3. PearlandAggie says:

    You don’t really think actual data is going to change their minds, do you?

  4. Scott Scarborough says:

    OK, I’ll try:
    1) ~0.01 atm
    2) Liquid, vapor, and Ice 1
    3) ~ 0.003 atm
    4) Ice 1 and Vapor
    5)~0.02 atm
    6) Liquid and Vapor
    7) ~0 deg C (tripple point)

    but I’m not a Chemist or an alarmist.

  5. suyts says:

    lol, All this to get back to applying the ideal gas law?…… i like it!

  6. AndyW says:

    Everytime I see one of these phase change diagrams I see CO2 snow appear before my eyes and Anthony Watts getting very upset with you Steve!

    Best leave alone me thinks.


  7. Eli Rabett says:

    Which lake? The answers for the big one out in Utah would surprise you, but the answer would not be what you think for most lakes anyhow for similar, but not so extreme reasons. #7 is equally interesting as Eli can find all three phases in a jar of his favorite beverage, just not at equilibrium

    In short, hire yourself a chemisto or a chemista.

  8. Eli Rabett says:

    Now some, not Eli to be sure, would think that anyone who thought that salt water freezes at 0 C was, well, let the bunny be blunt, an idiot, and that thingee out in Utah is, well the Great Salt Lake. Wonder why they call it that.

    Others, perhaps more experienced in the world would realize that all lakes have some ionized salts in them and could extrapolate from that to the thought that while pure water freezes at 0 C, maybe asking at what temperature a lake freezes at might require knowing something about the lake.

    Just saying you know.

    • Everyone understands that, you arrogant moron.

    • Scott says:

      Others, perhaps even more experienced in the real world would realize that it’s not just ionized salts that affect freezing point but neutral solutes too.

      Of course, those people might also be more experienced with this blog and not just trolling, so they’d know that all the topics just brought up have been discussed multiple times here. But if one really wanted to talk about the Great Salt Lake, try to figure out how the lake effect snow from it dominated the freak snows in the Rocky Mountains last winter.

      Now, I still don’t agree that the triple point matters all that much for the sea ice…


  9. Eli Rabett says:

    But Stevie, Eli is so unhappy that you object to his excellent auditing. Up to Engineering Standards too. We even can work in Rankine instead of that Commie Celsius stuff.

    • Did you escape from a mental institution recently?

    • suyts says:

      Eli, you’d probably be better received if you’d quit referring to yourself in the third person. Illeism is often indicative of an extreme narcissistic disorder. You should work on that. Or seek some help with it. Also, as Scott has pointed out, the issues you’ve brought up have already been discussed. Rankine? lol, very nice. Why not Rømer or Réaumur? Why don’t we stick to Kelvin, just for clarity’s sake? BTW Eli, bringing up stuff that is understood but not stated doesn’t reflect well on you or your bunny brigade. Gosh, you mean things are different at different locations? Whodda thunk? Thanks for bringing stuff like that up! Your contribution to the discussion is everything I’ve come to expect from you. Thanks again,


  10. M says:

    No! Look, anywhere along the liquid/vapor phase change line, the point is not that vapor and liquid coexist, but rather that they are at a key point where just a small increase in temperature will cause the liquid portion to boil, or a small decrease in temperature will cause the saturated atmosphere to condense. At 1 atmosphere, this key point is at 100 degrees C – eg, boiling. Yes, at 20 degrees C and 1 atmosphere, there is some water in the gas phase based on vapor pressure – this is _not_ the same as boiling, and therefore the water is _not_ on the liquid/vapor phase change line. In the same way, the triple point can only occur when the liquid is simultaneously at a temperature where it is boiling, freezing, and condensing. That just does not happen for water at 1 atmosphere of pressure. This is nothing to do with alarmism – this is just standard high school chemistry. (and, FYI, I have a graduate degree in chemistry)

    Do you really believe what you say, or are you just trolling? It seems hard to believe the former, and yet…

    • You are totally confused – boiling is a different issue. The vapor pressure of the water is the same at 0C, regardless of what the partial pressure of other gas constituents is. In a closed system it couldn’t boil because the atmospheric pressure would be identical to the vapor pressure.

      Instead of embarrassing yourself, try learning what you are talking about.

  11. Alan Travis says:

    First, the opportunity for discussion of something as ubiquitous and important to every person alive as water is wonderful. I did not learn enough, if I learned anything at all, about the triple point as I studied chemistry. But may I correct you, Steven. Water has four phases, not three.
    The fourth phase exists at high temperatures and high pressure, wherein water behaves both as a gas and as a liquid.

    Now here is a question for everyone. It first occured to me in high school, but I accepted what I was told then. You can’t always do that.

    At what ambient temperature does water freeze?
    Corollary question: At what ambient temperature does ice melt?

  12. Alan Travis says:

    StevenGoddard wrote: In a closed system it couldn’t boil because the atmospheric pressure would be identical to the vapor pressure.

    But isn’t that precisely the case at 760 torr, where the atmospheric pressure is identical to the vapor pressure of water at 100C? Water boils at that exact point, does it not?

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