Definitions Flashcards
Define equilibrium
A state of system where no net force or heat flow exists.
Define enthalphy
The total heat content of a system - a combination of microscopic internal energy and macroscopic flow work
Define property
A value that can be used to define an equilibrium.
What is a thermodynamic temperature scale?
A scale of temperature measurement that is independent of any substance’s thermometric properties, and which has an absolute zero.
What is the Clausius statement of the Second Law?
“It is impossible to construct a machine which in itself will cause thermal energy to pass from a cold reservoir to a hot reservoir”
Define polytropic process
A process for which it is viable to relate pressure and volume as pVⁿ = constant, where n is a given constant for a particular process
Define cyclic process
A process that always returns to the same equilibrium over the course of its operation
Define reversible process
A process that can be reversed without leaving any trace on its surroundings
What is the state postulate?
Equilibrium is specified if two independent intensive properties of the system are know
Define closed system (control mass)
A system of fixed mass which allows only energy transfers at its boundary i.e. which does not allow mass transfer at its boundary
Define open system (control volume)
A fixed region of space, for which both matter and energy may cross its boundary
Define intensive property
A property that is independent of the amount of matter within the system
Define extensive property
A property that is dependent upon the quantity of matter within the system
Define adiabatic
Involves no heat transfer
Define process
A system’s change from one equilibrium state to another
Define path
The series of states that a system passes through over the course of a process
Define quasi-equilibrium process
A process that is sufficiently slow such that the system undergoing it is able to adjust without any part of said system having any property different from another part within the system
Define isothermal
Constant temperature
Define isobaric
Constant pressure
Define isochoric/isometric
Constant volume
Define isentropic
Constant entropy
Define a steady-flow process
A process during which fluid flows through a control volume steadily
What is the Zeroth Law?
If two bodies are in thermal equilibrium with a third body, then they are also in thermal equilibrium with each other
What is heat?
The form of energy that is transferred between two systems as a consequence of a temperature difference
What is heat flow?
Transfer of thermal energy
What is the First Law?
Energy can be neither created nor destroyed, it can merely change form
What is the Kelvin-Planck statement of the Second Law?
It is impossible for any device that operates on a cycle to exchange heat with a single reservoir and produce a net amount of work
Define system
A quantity of matter or region of space selected for analysis
What is the Carnot efficiency?
The maximum efficiency a heat engine operating between two thermal reservoirs can have
Define internal energy
The sum of all forms of microscopic energy - a property of state that follows from the first corollary of the first law
Define entropy
A property of state that indicates a system’s degree of organisation and irreversibility (if that system is thermally isolated)
