Thermodynamics Final Flashcards
System
A quantity of matter or a region in space chosen for study
Surroundings
The mass or region outside the system
Boundary
The real or imaginary surface that separates the system from its surroundings. Can be fixed or movable.
Closed System (Control Mass)
A fixed amount of mass, and no mass can cross its boundary. Energy in the form of heat or work can cross. Volume doesn’t have to be fixed.
Open System (Control Volume)
A properly selected region in space, both mass and energy can cross its boundary. Fixed volume.
Control Surface
The boundaries of a control volume. It can be real or imaginary.
Property
Any characteristics of a system such as P, T, V, and m.
Intensive Properties
Those that are independent of the mass of a system, such as pressure, temperature, and density.
Extensive Properties
Those whose values depend on the size - or extent - of the system.
Specific Properties
Extensive properties per unit mass
Specific Gravity
The ratio of the density of a substance to the density of some standard substance at a specified temperature (usually water at 4 degrees C) NO UNIT
Specific Weight
The weight of a unit volume of a substance, HAS UNITS
Equilibrium
A state of balance
Thermal equilibrium
Same temperature throughout the entire system
Mechanical Equilibrium
No change in pressure at any point of the system with time
Phase Equilibrium
When the mass of each phase reaches an equilibrium level and stays there
Chemical Equilibrium
No chemical reactions occur
State Postulate
The state of a simple compressible system is completely specified by two independent, intensive properties.
Process
Any change that a system undergoes from one equilibrium state to another
Path
The series of states through which a system passes during a process
Cv
Specific heat at constant volume
Cp
Specific heat at constant pressure
Kelvin Planck
It is impossible for any device that operates on a cycle to receive heat from a single reservoir and produce a net amount of work
Clausius
It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to a higher temperature body. A refrigerator cannot operate unless its compressor is driven by an external power source, such as an electric motor.
