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First Law of Thermodynamics Terms

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*All page numbers are from Atkins, The Elements of Physical Chemistry, Second Edition
Term Page #* Definition/Explanation
adiabatic system 36 A system that is thermally isolated from its surroundings.
bomb calorimeter 46 A device used to accurately measure deltaU.
bond enthalpy 59 The molar enthalpy change accompanying the dissociation of a chemical bond.
calorimeter constant 46 The ratio of supplied heat to temperature change.
Classical thermodynamics 35 Thermodynamics developed during the nineteenth century that does not use the ideas of atoms and molecules.
closed system 36 A system that can exchange heat but not matter with its surroundings.
combustion 63 The reaction of a compound with oxygen.
condensation 54 The transition of a gas to a liquid. The reverse of vaporization.
conservation of energy 36 Energy cannot be created or destroyed.
constant-pressure heat capacity 48 The heat capacity for a system that is free to expand.
constant-volume heat capacity 48 The heat capacity for a system that cannot expand.
dissociation 59 The breaking of a chemical bond.
electron gain 58 The reverse of ionization, the gain of an electron on an atom (or ion).
electron gain enthalpy 58 The molar enthalpy change accompanying the addition of an electron to an atom (or ion).
endothermic 37 A process that absorbs heat from the surroundings.
endothermic compounds 67 They lie at a higher enthalpy than their component elements and have a positive standard enthalpy of formations.
energy 35 A property of matter that is the capacity to do work.
enthalpy 50 The enthalpy of a system, H, is defined as deltaH=q.
enthalpy of fusion 54 The enthalpy per mole of molecules that accompanies fusion.
enthalpy of ionization 56 The molar enthaply change accompanying the removal of an electron from a gas-phase atom (or ion).
enthalpy of sublimation 55 The molar enthalpy change accompanying sublimation.
enthalpy of vaporization 52 The heat that must be supplied at constant pressure per mole of molecules that a vaporized.
exothermic 37 A process that releases heat into the surroundings.
exothermic compounds 67 They lie at a lower enthalpy than their component elements and have a negative standard enthalpy of formations.
expansion work 39 Work done when a system expands against an opposing pressure.
first ionization enthalpy 56 The molar enthaply change accompanying the removal of an electron from a gas-phase atom.
First Law of thermodynamics 45 The internal energy of an isolated system is constant.
freezing 54 The transition of a liquid to a solid. The reverse of fusion.
fusion 54 The transition from solid to liquid, also called melting. The reverse process is freezing.
heat 37 The transfer of energy as a result of a temperature difference between the system and the surroundings.
heat capacity 47 The constant of proportionality between q and deltaT.
Hess's law 64 The standard enthalpy of a reaction is the sum of the standard enthalpies of the reactions into which the overall reaction may be divided.
internal energy 42 A method of keeping track of the energy of a system.
isolated system 36 A system that can neither exchange heat or matter with its surroundings.
Kirchoff's law 70 the relation between reaction enthalpies given by the equation:
deltarH0'=deltarH+deltarCpdeltaT
mean bond enthalpy 60 The average of a series of bond enthalpies for different compounds.
molar heat capacity 47 The heat capacity divided by the amount of substance.
open system 36 A system that can exchange matter with its surroundings.
reference state 66 The most stable state of an element under the prevailing conditions.
reversible 40 A change that can be reversed by an infinitesimal change in a parameter.
second ionization enthalpy 57 The molar enthaply change accompanying the removal of a second electron from a gas-phase or ion.
specific enthalpy 63 The heat released divided by the mass of the compound.
specific heat capacity 47 The heat capacity divided by the mass of the sample.
standard enthalpy of combustion 63 The standard change in enthalpy per mole of combustible substance.
standard enthalpy of formation 66 The standard enthalpy (per mole of substance) of a for its formation from its elements in their reference states.
standard reaction enthalpy 68 The difference between the standard enthalpies of formation of the reactants and the products, with each term weighted by the stoichiometric number in the chemical equation.
standard state 62 The state of a pure substance at exactly 1 bar.
state function 45 A physical property that depends only on the current state of the system and is independent of the path by which the state was reached.
statistical thermodynamics 35 The theory connecting bulk and atomic thermodynamic properties.
sublimation 55 The direct conversion of a solid to a vapor. The reverse process of vapor deposition.
surroundings 36 Everything outside of the system; this is where we make out observations.
system 36 The part of the world that we have interest in.
thermochemical equation 53 An equation that show the enthaply change that accompanies the conversion of an amount of reactant equal to its stoichiometric coefficient in the accompanying chemical equation.
thermochemistry 62 The study of the heat required or absorbed by chemical reactions.
thermodynamics 35 The study of the transformation of energy.
vapor deposition 55 The direct conversion of a vapor to a solid. The reverse process of sublimation.
work 37 A transfer if energy that can be used to change the height of a weight somewhere in the surroundings.
*All page numbers are from Atkins, The Elements of Physical Chemistry, Second Edition


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