States of matter & Phase Equilibria

1. Khalid T Maaroof
MSc. Pharmaceutical sciences
School of pharmacy – Pharmaceutics department
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Online access: bit.ly/physicalpharmacy
Phase equilibria
Physical Pharmacy
10/31/2015

2. What was equilibrium?
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3. 3

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5. Phase rule
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 Coexistence of phases can only occur over a limited
range.
 phase rule is a relationship for determining the least
number of intensive variables that can be changed
without changing the equilibrium state of the system.
 P is the number of phases present
 F is termed the number of degrees of freedom
 C in represents the number of components in the system
What is intensive variable???

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 The number of degrees of freedom: is the least
number of intensive variables that must be
fixed/known to describe the system completely.
 Examples of intensive variables are: temperature,
pressure, concentration….

7. Systems Containing One Component
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8. This is the phase diagram for a typical pure substance.
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9. at higher pressure, the melting temperature would be
higher because the line between the solid and liquid
areas slopes slightly forward.
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10. Increasing pressure at constant temperature
changes liquid to solid and vice versa
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11. The same explanation for liquid vapour
boundary
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12. The point labelled as C in the phase diagrams is critical
temperature.
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 Note the process of
sublimation as shown on
the graph; below the point
T.
 Point T is called triple
point.
 Where all three lines meet,
you must have a unique
combination of temperature
and pressure where all
three phases are in

13. Normal melting and boiling points
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14. The phase diagram for water
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 In the case of water, the
melting point gets lower at
higher pressures. Why?

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16. Imagine lowering the pressure on liquid
water along the line in the diagram below.
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17. Systems Containing more than one
Component
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18. CONDENSED SYSTEMS
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 a maximum of three degrees of freedom is possible in
a two-component system.
 More components more degrees of freedom
 In two component one phase system (maximum no of
variables) F = 2 – 1 + 2 = 3
 E.g. temperature, pressure, and concentration
 we frequently choose to disregard the vapor phase
and work under normal conditions of 1 atm pressure.
 Now we can use planar figures instead of three
dimensional (this will be easier)
 condensed systems: When we only consider solid
and liquid phases

19. Two-Component Systems Containing Liquid
Phases
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The maximum
temperature at which
the two-phase region
exists is termed the
critical solution or
(upper consolute
temperature).

20. Upper and lower consulate temperatures
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21. Two-Component Systems Containing Solid
and Liquid Phases: Eutectic Mixtures
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 two components are completely miscible in the liquid
state and completely immiscible as solids,

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23. Eutectic composition
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 “contact melting”: lowest melting temperature over
a composition range.
 eutectic composition is the composition of two or
more compounds that exhibits a melting temperature
lower than that of any other mixture of the
compounds
 The primary criterion for eutectic formation is the
mutual solubility of the components in the liquid or
melt phase.
 Lidocaine and prilocaine, two local anesthetic
agents, form a 1:1 mixture having a eutectic
temperature of 18◦C

24. Phase Equilibria in Three-Component Systems
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 In systems containing three components but only one
phase.
 four degrees of freedom are temperature, pressure,
and the concentrations of two of the three
components.
 Only two concentration terms are required because the
sum of these subtracted from the total will give the
concentration of the third component.
 Temperature and pressure are considered to be

25. 25
Triangular
Diagram

26. Ternary Systems with One Pair of Partially Miscible
Liquids
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e.g. Water and
benzene + alchohol
• Alchohol provide
solvation
• binodal curve

27. Alterations of the binodal curves with
changes in temperature.
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28. Ternary Systems with Two Pairs of Partially
Miscible Liquids
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29. Ternary Systems with Three Pairs of Partially
Miscible Liquids
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F=0 Why???

30. Questions !
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