Properties of Saturated Water Question 3

[atotiace]

This is my first post on this site. I had a question about saturated water properties. If you know the temperature of water and you are looking at a table of properties. What does it mean if your pressure is above the saturation pressure. Does that mean it is super heated vapor or incompressible liquid? I never could get a grasp on that.

 

[Latexman]

Sub-cooled liquid.

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

 

[chicopee]

It also means that the water is compressed above its saturation pressure in that liquid region.

 

[25362]

Looking at a phase diagram one can see that even at 27^oC (~300 K) liquid water can be transformed into a solid (type 6 ice) at a pressure of 10⁹ Pa.

 

[25362]

In addition, from the same diagram, one sees that vapor at 400 K, can be condensed at ~10⁶ Pa, and the liquid can be solidified, at the same temperature, at a pressure of 10¹⁰ Pa, to type VII ice.

 

[atotiace]

Thanks everyone for all the quick responses. That makes sense when I think about it. Now how can I tell if a substance is a mixture looking at the same chart. Let's say my given information is a known T and p. My p is below my saturation p does that mean it a mixture? If not, how can I tell based on those two properties whether or not I'm dealing with a mixture if I'm just looking at a table of information.

 

[25362]

If I'm not mistaken your term "mixture" refers to the presence of more than one stable phase.

The lines on a P/T phase diagram represent equilibrium between coexisiting phases. As long as you stay on the lines, by changing T and P as needed, the phases will continue appearing.

Assuming these lines are neither vertical nor horizontal, changing only one parameter, may move the system away from equilibrium into a single phase zone.

I suggest to have a look at the phase rule (in wikipedia or any general chemistry text).

 

[BernardRhodes]

Late to the party but anyway:

Further to atotiace's post on 7 October:

If the pressure is below the saturation pressure then the substance is superheated vapour.

Only when the pressure corresponds exactly to the saturation temperature is it possible for there to be a mixture of liquid and vapour.