Chapter 2 The Structure of Thermodynamics

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Chapter 2The Structure of Thermodynamics

• Notes on
• Thermodynamics in Materials Science
• by
• Robert T. DeHoff
• (McGraw-Hill, 1993).

2
Thermodynamic Systems

• System --- That portion (subset) of the universe
  that is under study.
• Surroundings --- Everything else. Usually, only
  the interaction with the immediate surroundings
  is relevant.

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Classification of Systems

• Unary versus Multicomponent --- How many unique
  chemical species?
• Homogeneous versus Heterogeneous --- How many
  unique phases?
• Closed versus Open --- Is matter exchanged with
  the surroundings?
• Non-reacting versus Reacting --- Can chemical
  reactions occur?
• Otherwise Simple versus Complex --- Are only
  chemical, thermal, or mechanical effects
  involved? Are fields, surfaces, or elastic
  effects involved?

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2.1 Classify the following thermodynamic systems

• A solid bar of copper
• Unary Multicomponent
• Homogeneous Heterogeneous
• Closed Open
• Non-reacting Reacting
• Otherwise simple Complex

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2.1 Classify the following thermodynamic systems

• A glass of ice water
• Unary Multicomponent
• Homogeneous Heterogeneous
• Closed Open
• Non-reacting Reacting
• Otherwise simple Complex

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2.1 Classify the following thermodynamic systems

• An yttria stabilized zirconia furnace tube.
• Unary Multicomponent
• Homogeneous Heterogeneous
• Closed Open
• Non-reacting Reacting
• Otherwise simple Complex

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2.1 Classify the following thermodynamic systems

• A styrofoam coffee cup
• (just the polymer)
• Unary Multicomponent
• Homogeneous Heterogeneous
• Closed Open
• Non-reacting Reacting
• Otherwise simple Complex

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2.1 Classify the following thermodynamic systems

• A styrofoam coffee cup
• (the polymer and enclosed gas)
• Unary Multicomponent
• Homogeneous Heterogeneous
• Closed Open
• Non-reacting Reacting
• Otherwise simple Complex

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2.1 Classify the following thermodynamic systems

• A eutectic alloy turbine blade rotating at 20,000
  rpm
• Unary Multicomponent
• Homogeneous Heterogeneous
• Closed Open
• Non-reacting Reacting
• Otherwise simple Complex

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Thermodynamic Properties

• State Variables --- Values are determined by
  current condition are independent of path.
• Process Variables --- Have meaning only for
  changing systems.
• Intensive Properties --- Have a value at each
  point in a system. May vary from point to point.
  Do not depend on the amount of matter.
• Extensive Properties --- Values apply to the
  whole system. Depend on the amount of matter.

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2.2 Without state functions thermodynamics would
be useless. Discuss this assertion.

• If there no state functions (like T, P, V,
  composition) then the behavior of all aspects of
  matter would depend explicitly on the history of
  the system.
• There would be no variables that, by themselves,
  explicitly describe the current condition of any
  system.
• Even the history experienced by the system could
  not be described in terms of some sequence of its
  properties.

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2.4 Why is heat a process variable?

• Heat is fundamentally a flow of energy. Heat is
  transferred between two systems, or between parts
  of the same system.
• The rearrangement of the distribution of energy
  is accompanied by changes in at least some of the
  properties of the system.
• Such a change is a process

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Thermodynamic Properties

• State Variables --- Values are determined by
  current condition are independent of path.
• Process Variables --- Have meaning only for
  changing systems.
• Intensive Properties --- Have a value at each
  point in a system. May vary from point to point.
  Do not depend on the amount of matter.
• Extensive Properties --- Values apply to the
  whole system. Depend on the amount of matter.

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2.3 Determine which of the following properties
of a thermodynamic system are extensive/intensive

• The mass density.
• M/L3
• Kg/m3

Intensive Extensive
Intensive
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2.3 Determine which of the following properties
of a thermodynamic system are extensive/intensive

• The molar density.
• M/L3
• Moles/m3

Intensive Extensive
Intensive
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2.3 Determine which of the following properties
of a thermodynamic system are extensive/intensive

• The number of gram atoms of alumina in a chunk of
  alumina.
• M
• Moles

Intensive Extensive
Extensive
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2.3 Determine which of the following properties
of a thermodynamic system are extensive/intensive

• The potential energy of the system in a
  gravitational field.
• ML2/t2
• J

Intensive Extensive
Extensive
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2.3 Determine which of the following properties
of a thermodynamic system are extensive/intensive

• The molar concentration of NaCl in a salt
  solution.
• M/L3
• Moles/m3

Intensive Extensive
Intensive
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2.3 Determine which of the following properties
of a thermodynamic system are extensive/intensive

• The heat absorbed by a gas in a cylinder when it
  is compressed.
• M L2/t2
• J

Intensive Extensive
Extensive
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Thermodynamic Relations

• Laws --- 0th, 1st, 2nd, 3rd
• Definitions --- Energy, , Compressibility, ...
• Coefficient Relations --- Z Z(w,x,y,)
• Maxwell Relations ---
• Criteria for Equilibrium --- DS maximum
• Conditions for Equilibrium --- Ta Tb ,...