# Glossary of Thermodynamic Terms

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I
 Primary Word Secondary Word Definition Tutorial Page Link
 ideal critical molar volume The molar volume at of a pure substance predicted by the Ideal Gas EOS at the critical temperature and pressure of that substance.  [ L/mol ] 2E8 ideal gas A gas that obeys the ideal-gas equation of state. All real gases approach ideality at low pressures and high temperatures.  For most gases, less than 1% error is incurred by treating them as ideal gases as long as the molar volume is greater than 20 L/mole.  Diatomic gases and most noble gases can be treated as ideal gases as long as their molar volume exceeds 5 L/mole. 2D2 ideal gas boundary work 4A18  ,  19 ideal gas enthalpy 3A7, 3B17 - 22, ideal gas enthalpy change 3D6 - 13 ideal gas heat capacity 3C3  ,  5 - 7  ,  10 - 12 ideal gas internal energy 3A3, 3B17 - 22, ideal gas property change 3D5 ideal gas enthalpy 7E3 ideal gas entropy function 7D13 - 14, 7E1 - 4, ideal gas EOS The simplest EOS :  PV=nRT.  It is accurate to within 1% when the molar volume of a gas exceeds 20 L/mole.  It can be used accurately for diatomic gases and most noble gases as long as the molar volume exceeds 5 L/mole 2E2 - 5, 4A18, 6F8 ideal gas equation of state applicability 2E4 ideal gas internal energy 7E3 ideal gas property table 7D13 - 14, 7E3  ,  4, ideal gas thermometer 6F7 ideal process 6A7 ideal reduced molar volume The ratio of the molar volume of a substance to the ideal critical molar volume of the same substance. 2E9 immiscible Two components that are not soluble with each other in a liquid phase.  A familiar example is a mixture of water and oil. 2A6 immiscible liquids Two liquids that are not soluble with each other in a liquid phase.  A familiar example is a mixture of water and oil. 2A6 incompressible liquid The volume of an incompressible liquid does not change when the pressure changes.  As a result, the density, specific volume and molar volume of an incompressible liquid are not functions of pressure. 3A4 incompressible liquid heat capacity 3D14 - 17 incompressible liquid internal energy 3A4 incompressible liquid property change 3D14 - 17 incompressible substance The volume of an incompressible substance does not change when the pressure changes.  As a result, the density, specific volume and molar volume of an incompressible substance are not functions of pressure. 3A4 inexact differential The differentials of path functions, such as heat and work, are inexact differentials.  They are represented using a "squiggly-d" as a prefix. 4A7 - 8  ,  12, 4B10, 7A2 injection work 5B6 intensive property Properties of a system that are independent of the size of the system.  This means that if you could magically divide the system into two equal subsystems and then measure the value of the property in one of the subsystems, the value that you measured would be the same as the value of that property in the original system.  Temperature, pressure, molar volume and molar enthalpy are examples of intensive properties. 3C4, 3D1, 7B3 internal combustion 9E2  ,  3 Internal energy Is related to the molecular structure and the degree of molecular activity and is defined as the sum of all the microscopic forms of energy of a system (kinetic and potential energies of the molecules). 1A4, 3C2, 4B2  ,  3 internal energy ideal gas 3A4 internally reversible 6D9 interpolation double 2C20  ,  21 interpolation linear 2C6 - 12 irreversibility friction 6D5 irreversibility heat engine 7A6 irreversibility heat pump 7A6 irreversibility heat transfer Is related to the molecular structure and the degree of molecular activity and is defined as the sum of all the microscopic forms of energy of a system (kinetic and potential energies of the molecules). 6D4 irreversibility mixing 6D7 irreversibility rapid compression 6D6 irreversibility rapid expansion 6D6 irreversibility refrigerator 7A6 irreversibility sources of 6D 3 -7 irreversible process 6D2 isentropic efficiency 8C1 - 19, 8D1, isentropic efficiency compressor 8C9 isentropic efficiency nozzle 8C7  ,  8 isentropic efficiency turbine 8C3 - 6 isentropic process 7E1 - 7 isentropic process ideal gas, constant heat capacity ratio 7E5  ,  6 isentropic process logarithmic TS diagram 7E9 isentropic process semi-logarithmic PV diagram 7E9 isobar A curve on a Phase Diagram that is a collection of points or states that all exist at the same pressure. 2B5 isobar TS diagram 7B9 isobaric process A process during which the pressure remains constant. 1D3, 4E1 - 3, isobaric process logarithmic TS diagram 7E10 isobaric process semi-logarithmic PV diagram 7E10 isochor TS diagram 7B9 isochoric process A process during which the volume of the system remains constant. 1D3, 4E1 - 2  ,  5, isochoric process logarithmic TS diagram 7E12 isochoric process semi-logarithmic PV diagram 7E12 isotherm A curve on a Phase Diagram that is a collection of points or states that all exist at the same temperature. 2B6, 2F5, isothermal compression 8C12 isothermal efficiency 8C15  ,  16 isothermal process A process during which the temperature remains constant. 1D3, 4A17 - 18, 6F9  ,  12 isothermal process logarithmic TS diagram 7E11 isothermal process semi-logarithmic PV diagram 7E11