Phase Diagrams

Diagram

Phase Diagrams.png

Info

  • Triple point: the temperature and pressure at which all three phases of the substance can co-exist in thermodynamic equilibrium
  • Normal boiling point: temperature at which the vapour pressure is equal to
  • Critical point: from this temperature point forward, no matter what pressure we apply, we cannot liquify the gas

Example

Identify whether each of the following statements is true or false:

  1. A one-component phase diagram has a single triple point where solid, liquid and vapour phases co-exist.
    • T
  2. A one-component phase diagram has a single critical point above which the liquid phase does not exist.
    • T
  3. A liquid will boil (i.e. the vapour pressure above the liquid equals the total pressure) at a single temperature.
    • F
  4. At a given pressure, above the triple point pressure, the solid phase melts at a single temperature.
    • T
  5. At a given temperature (between the triple point and the critical temperature) vapour will begin to condense to liquid at a single pressure.
    • T

Polymorphism

Definition

Polymorphism is the existence of a solid in more than one state

Phase Diagram for Water

Diagram

Phase Diagrams_0.png

Observations:

Example

Phase Diagrams_1.png

Identify whether each statement is A) TRUE or B) FALSE:

  1. There is a single triple point at which three phases are in equilibrium.
    • F
  2. Mercury(II) iodide has a normal boiling point.
    • T
  3. At temperatures below , mercury(II) iodide does not melt.
    • T
  4. The vapour pressure of mercury(II) iodide at any given temperature could be determined from this phase diagram, if the axis were drawn to scale.
    • T
  5. As pressure increases the sublimation temperature of mercury(II) iodide increases.
    • T