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PHASE DIAGRAMS

A map to the state of a substance

Vincent Van Gogh, Starry Night Over the Rhone

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THE PHASE OF A SUBSTANCE DEPENDS ON TWO PROPERTIES OF THE SUBSTANCE:

The Temperature:

the average kinetic energy of the particles of the substance

The Pressure:

the force per unit area acting on the substance

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THE PHASE OF A SUBSTANCE DEPENDS ON TWO PROPERTIES OF THE SUBSTANCE:

The Temperature:

Units – oC, K, and oF

How do you think temperature would affect the phase of a substance in terms of particle speed, spacing, and IMFs?

The Pressure:

Units – atm, psi, and kPa

How do you think pressure would affect the phase of a substance in terms of particle speed, spacing, and IMFs?

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PHASE CHANGES ON PHASE DIAGRAMS

  1. Notice that the scales are not linear.
  2. What happens as pressure stays constant and temperature changes?
  3. What happens as temperature stays constant and pressure changes?
  4. Look at the pressure below A…what is unique there?
  5. What do you think is meant by “triple point”?

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PHASE DIAGRAM FOR CO2 VS. H2O

CO2 Phase Diagram

H2O Phase Diagram

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THE TRIPLE POINT OF WATER DEMONSTRATION

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PHASE DIAGRAM OF H2O

What do you see in the shape of water’s phase diagram that is quite different from the CO2 phase diagram?

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SUPERCRITICAL FLUID OF CO2 DEMONSTRATION