Problem reading thermodynamic tables

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SUMMARY

The discussion centers on the behavior of substances in thermodynamic equilibrium, specifically regarding the relationship between pressure and saturation pressure at a given temperature. When pressure is less than the saturation pressure, the substance exists as overheated vapor, while exceeding the saturation pressure results in a compressed liquid. The equilibrium state allows for both phases to coexist, but altering pressure through volume changes leads to phase transitions, ultimately resulting in either complete vaporization or condensation depending on the direction of pressure change.

PREREQUISITES
  • Understanding of thermodynamic principles
  • Familiarity with phase equilibrium concepts
  • Knowledge of saturation pressure and its significance
  • Basic grasp of vapor-liquid interactions
NEXT STEPS
  • Study the Clausius-Clapeyron equation for phase transitions
  • Learn about the properties of saturated and superheated steam
  • Explore the use of thermodynamic tables for various substances
  • Investigate the implications of pressure-volume work in thermodynamic systems
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Students and professionals in thermodynamics, chemical engineering, and mechanical engineering who seek to deepen their understanding of phase behavior and thermodynamic properties of substances.

Sly37
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Hi!
I have trouble understanding this:
Given Temperature:
If pressure < saturation pressure => Overheated Vapor
If pressure > saturation pressure =>Compressed Liquid


Why does this happen??

Thanks in advance!
 
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At a given temperature, you can have both pure vapor and pure liquid present together in equilibrium if the pressure is equal to the equilibrium vapor pressure at that temperature. If you try to increase the pressure by reducing the volume of a fixed amount of liquid and vapor, you won't be able to do it. You will just cause some of the vapor to condense and form more liquid. However, eventually, you will cause all the vapor to condense. After that you will be able to increase the pressure, since only liquid will be remaining.

If you try to decrease the pressure by increasing the volume of a fixed amount of liquid and vapor, you won't be able to do ti. You will just cause some of the liquid to evaporate and form more vapor. However, eventually, youwill cause all the liquid to evaporate. After that, you will be able to reduce the pressure, since only vapor will be remaining. This will be referred to as superheated vapor.
 

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