thermodynamics of surfaces and interfaces
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Thermodynamics of Surfaces and Interfaces. What is thermodynamics dealing with?. Thermodynamics is the branch of science that id concerned with the principles of energy transformation in macroscopic system. - PowerPoint PPT PresentationTRANSCRIPT
Thermodynamics of Surfaces and Interfaces
Thermodynamics of Surfaces and InterfacesWhat is thermodynamics dealing with?Thermodynamics is the branch of science that id concerned with the principles of energy transformation in macroscopic system.Macroscopic properties of matter arise from the behavior of a very large number of molecules.Thermodynamics is based upon experiments and observation , summarized and generalized in the laws of thermodynamics.These laws are not derivable from any other principles: they are in fact improvable and therefore can be regarded as assumptions only.
Some DefinitionsIntensive variablesExtensive variables System, isolated, open, closedSurroundingsBoundaryEquilibrium ProcessThermodynamic stateEquilibrium between phases in heterogeneous closed systemWhat does equilibrium mean?A system is in eq if no further spontaneous changes takes place and if the same state can be reached by other directions.A phase?A phase equilibrium is defined when the same species are present in different phases.A heterogeneous closed systems is composed of two or more phases, with each phase is considered as an open system within an overall closed system.Equilibrium between phases in heterogeneous closed systemIf the system initially, is not in an internal eq, then any process should occur in irreversible direction.So, according to first law:
And, combining with Clausius inequality: (for both reversible and irreversible processes)
Equilibrium between phases in heterogeneous closed systemOr finally:
Equilibrium between phases in heterogeneous closed system
Equilibrium between phases in heterogeneous closed system
Equilibrium between phases in heterogeneous closed system
Equilibrium between phases in heterogeneous closed system
Equilibrium between phases in heterogeneous closed system
Equilibrium between phases in heterogeneous closed system
Wettability and Contact AngleReference:
Wettability and contact angle
In the case of a liquid that forms a uniform film (i.e., where = 0), the solid is said to be completely wetted by the liquid, or that the liquid wets the solid.Where a nonzero angle is formed, there exists some controversy as to how to describe the system. If a finite contact angle is formed (> 0), some investigators describe the system as being partially wetted.Others prefer to make a distinction based on the size of the contact angle. For example, a given worker may define as wetting any liquid that produces a contact angle of 30 or less on a solid. Between 30 and 89 the system would be partially wetting, and 90 and above nonwetting. Alternatively, any system with 0