Key Terms
- Carnot cycle
- cycle that consists of two isotherms at the temperatures of two reservoirs and two adiabatic processes connecting the isotherms
- Carnot engine
- Carnot heat engine, refrigerator, or heat pump that operates on a Carnot cycle
- Carnot principle
- principle governing the efficiency or performance of a heat device operating on a Carnot cycle: any reversible heat device working between two reservoirs must have the same efficiency or performance coefficient, greater than that of an irreversible heat device operating between the same two reservoirs
- Clausius statement of the second law of thermodynamics
- heat never flows spontaneously from a colder object to a hotter object
- coefficient of performance
- measure of effectiveness of a refrigerator or heat pump
- cold reservoir
- sink of heat used by a heat engine
- disorder
- measure of order in a system; the greater the disorder is, the higher the entropy
- efficiency (e)
- output work from the engine over the input heat to the engine from the hot reservoir
- entropy
- state function of the system that changes when heat is transferred between the system and the environment
- entropy statement of the second law of thermodynamics
- entropy of a closed system or the entire universe never decreases
- heat engine
- device that converts heat into work
- heat pump
- device that delivers heat to a hot reservoir
- hot reservoir
- source of heat used by a heat engine
- irreversibility
- phenomenon associated with a natural process
- irreversible process
- process in which neither the system nor its environment can be restored to their original states at the same time
- isentropic
- reversible adiabatic process where the process is frictionless and no heat is transferred
- Kelvin statement of the second law of thermodynamics
- it is impossible to convert the heat from a single source into work without any other effect
- perfect engine
- engine that can convert heat into work with efficiency
- perfect refrigerator (heat pump)
- refrigerator (heat pump) that can remove (dump) heat without any input of work
- refrigerator
- device that removes heat from a cold reservoir
- reversible process
- process in which both the system and the external environment theoretically can be returned to their original states
- third law of thermodynamics
- absolute zero temperature cannot be reached through any finite number of cooling steps