A portion of the system whose properties and composition are homogeneous and which is physically distinct from other parts of the system. (Water in liquid or vapor state is single phase. Ice floating on water is an example two phase system).
- Component
The different element or chemical compound which makes up the system.
- Composition
The relative amounts of each component.
-Phase Diagram
Is a graphical representation of the values of the thermodynamic variables when equilibrium is established among the phases of a system.
(phase ----- Component ------ Composition % ? + % ? )
The Gibbs Phase Rule
The geometry of all types of phase diagrams is governed by the Gibbs Phase Rule.
which applies to any system at equilibrium: If a system containing C components and P phases is in equilibrium, the number of degrees of
freedom F is given by
F = C – P + 1
P: number of phase, F: degree of freedom, an intensive variable such as T, P, XA,…,
C: number of component.
Examples to use Gibbs phase rule
- For a binary system (F = C- P + 1)
- Degree of freedom region: 1 is F = 2 - 1 + 1 ? F = 2
-Degree of freedom region: 2 is F = 2- 2 + 1 ? F = 1
-Degree of freedom region: 3 F = 2 -3 + 1 ? F = 0
Example: Using the phase rule, determine the degrees of freedom
1-at point( e).
2- within the field A + B.
3- within the field A + L
phase diagram, which summarizes the effect of temperature and pressure on a substance in a closed container. Every point in this diagram represents a possible combination of temperature and pressure for the system. The diagram is divided into three areas, which represent the solid, liquid, and gaseous states of the substance.
Along AB line:rate at which solid sublimes to form a gas=rate at which gas condenses to form a solid.
Along BC line:rate at which liquid boils to form a gas=rate at which gas condenses to form a liquid.
Along BD line:rate at which solid melts to form a liquid=rate at which liquid freezes to form a solid.
Point B in this phase diagram represents the only combination of temperature and pressure at which a pure substance can exist simultaneously as a solid, a liquid, and a gas. It is therefore called the triple point of the substance, and it represents the only point in the phase diagram in which all three states are in equilibrium. Point C is the critical point of the substance, which is the highest temperature and pressure at which a gas and a liquid can coexist at equilibrium.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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