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Key Terms

PhysicsKey Terms

Boltzmann constant
constant with the value k = 1.38×10−23 J/K, which is used in the ideal gas law
cyclical process
process in which a system is brought back to its original state at the end of every cycle
measurement of a system's disorder and how much energy is not available to do work in a system
first law of thermodynamics
states that the change in internal energy of a system equals the net energy transfer by heat into the system minus the net work done by the system
heat engine
machine that uses energy transfer by heat to do work
heat pump
machine that generates the heat transfer of energy from cold to hot
ideal gas law
physical law that relates the pressure and volume of a gas to the number of gas molecules or atoms, or number of moles of gas, and the absolute temperature of the gas
internal energy
sum of the kinetic and potential energies of a system’s constituent particles (atoms or molecules)
force per unit area perpendicular to the force, over which the force acts
second law of thermodynamics
states that the total entropy of a system either increases or remains constant in any spontaneous process; it never decreases
thermal efficiency
ratio of useful energy output to the energy input
thermal equilibrium
condition in which heat no longer transfers energy between two objects that are in contact; the two objects have the same temperature
zeroth law of thermodynamics
states that if two objects are in thermal equilibrium, and a third object is in thermal equilibrium with one of those objects, it is also in thermal equilibrium with the other object
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