Themes > Science > Physics > Thermodynamics > Laws of Thermodynamics Basic Significance > Primarily Condensed Phases > Types of Phase Diagrams

Phase diagrams are a graphical representation of three types of information:
  1. number of phases present
  2. composition of each phase
  3. quantity of each phase
Phase diagrams can be grouped according to how the information is presented; i.e., what types of variables are being graphically represented:

j = intensive variable; P, T, µ (chemical potential), electrical potential, etc.
q = extensive variable; V, S (entropy), ni (number of moles), Q (charge), etc.

    Type 1 Phase Diagram

    j1 vs j 2
    e.g., P vs. T; T vs. µ1

    Type 2 Phase Diagram

    j1 vs. q2/q3 or q2/(q2+q3)
    e.g., T vs. n1/n1+ n2 (where n1/n1+ n2 is X1, mole fraction of component 1)

    Type 3 Phase Diagram

    q1/q3 vs. q2/q3
    e.g., nO /(nCo + nNi ) vs. nNi/(nCo+ nNi ) for NiO-CoO system


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