physical chemistry chapter 1-4 vocab

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physical state
a substance's physical condition; is defined by its physical properties
mechanical equilibrium
the condition of equality of pressure on either side of a shared movable wall
equation of state
an equation that interrelates the variables that define the state of a substance
limiting law
Boyle's and Charles's Laws are examples of this. a law that is strictly true only in a certain limit, in this case p → 0
a line in a graph that corresponds to a single temperature
a line in a graph that corresponds to a single pressure
a line in a graph that corresponds to a single volume
perfect gas
a gas that obeys the perfect gas law under all conditions
dalton’s law
states that the pressure exerted by a mixture of (perfect) gases is the sum of the pressures that each one would exert if it occupied the container alone
kinetic model
for a gas, considers only the contribution to the energy from the kinetic energies of the molecules
root-mean-square speed
Important results from the model include expressions for the pressure and this. speed V of the molecules of an ideal gas is given by the expression, v=sqrt(3RTM)
Maxwell–Boltzmann distribution of speeds
gives the fraction of molecules that have speeds in a specified range
collision frequency
the average number of collisions made by a molecule in an interval divided by the length of the interval
mean free path
the average distance a molecule travels between collisions
compression factor
The extent of deviations from perfect behaviour is summarized by introducing this. it is a measure of how much the thermodynamic properties of a real gas deviate from those expected of an ideal gas
virial equation
an empirical extension of the perfect gas equation that summarizes the behaviour of real gases over a range of conditions
critical behaviour
The isotherms of a real gas introduce this concept. the physics of critical points.
critical temperature
A gas can be liquefied by pressure alone only if its temperature is at or below this point
van der Waals equation
a model equation of state for a real gas expressed in terms of two parameters, one representing molecular attractions and the other representing molecular repulsions. captures the general features of the behaviour of real gases, including their critical behaviour
reduced variables
The properties of real gases are coordinated by expressing their equations of state in terms of these
the process of achieving motion against an opposing force
the capacity to do work
exothermic process
a process that releases energy as heat
endothermic process
a process in which energy is acquired as heat
the process of transferring energy as a result of a temperature difference
work, heat
In molecular terms, _______ is the transfer of energy that makes use of organized motion of atoms in the surroundings and _______ is the transfer of energy that makes use of their disorderly motion
internal energy
the total energy of a system; is a state function. increases as the temperature is raised
equipartition theorem
can be used to estimate the contribution to the internal energy of each classically behaving mode of motion
First Law
states that the internal energy of an isolated system is constant
free expansion
expansion against zero pressure. does no work.
reversible change
a change that can be reversed by an infinitesimal change in a variable
reversible expansion
To achieve this, the external pressure is matched at every stage to the pressure of the system
energy transferred as heat, internal energy
The _______ at constant volume is equal to the change in _______ of the system
the measurement of heat transactions
energy transferred as heat at constant pressure is equal to the change in this of a system
heat capacity at constant pressure
equal to the slope of enthalpy with temperature
standard enthalpy of transition
equal to the energy transferred as heat at constant pressure in the transition under standard conditions
standard state
the pure form at 1 bar of a substance at a specified temperature
thermochemical equation
a chemical equation and its associated change in enthalpy
Hess’s law
states that the standard reaction enthalpy is the sum of the values for the individual reactions into which the overall reaction may be divided
standard enthalpies of formation
these are defined in terms of the reference states of elements
reference state
most stable state at the specified temperature and 1 bar for an element
standard reaction enthalpy
the difference of the standard enthalpies of formation of products and reactants
Kirchhoff’s law
the temperature dependence of a reaction enthalpy is expressed by this
internal pressure
the variation of internal energy with volume at constant temperature
Joule’s experiment
showed that the internal pressure of a perfect gas is zero
temperature, volume
the change in internal energy may be expressed in terms of changes in _______ and _______
Joule–Thomson effect
the change in temperature of a gas when it undergoes isenthalpic expansion
a signpost of spontaneous change: the entropy of the universe increases in a spontaneous process
entropy, reversible
A change in _______ is defined in terms of _______ heat transactions
Boltzmann formula
defines entropy in terms of the number of ways that the molecules can be arranged amongst the energy states, subject to the arrangements having the same overall energy
Carnot cycle
used to prove that entropy is a state function
This of a heat engine is the basis of the definition of the thermodynamic temperature scale and one realization of such a scale, the Kelvin scale
Clausius inequality
used to show that the entropy of an isolated system increases in a spontaneous change and therefore that its definition is consistent with the Second Law
spontaneous, equilibrium
_______ processes are irreversible processes; processes accompanied by no change in entropy are at _______
entropy, isothermally
the _______ of a perfect gas increases when it expands _______
enthalpy of transition
the change in entropy of a substance accompanying a change of state at its transition temperature is calculated from its _______
heat capacity
the increase in entropy when a substance is heated is calculated from its _______
Nernst heat theorem
states that the entropy change accompanying any physical or chemical transformation approaches zero as the temperature approaches zero: ΔS → 0 as T → 0 provided all the substances involved are perfectly ordered
third Law of thermodynamics
states that the entropy of all perfect crystalline substances is zero at T = 0
residual entropy
the entropy arising from disorder that persists at T = 0 for a solid
third-law entropies
entropies based on S(0) = 0
standard entropies of ions in solution
based on setting S^⦵(H+, aq) = 0 at all temperatures
standard reaction entropy
ΔrS^⦵ the difference between the molar entropies of the pure, separated products and the pure, separated reactants, all substances being in their standard states
criteria for spontaneous change
The Clausius inequality implies a number of _______ under a variety of conditions which may be expressed in terms of the properties of the system alone; they are summarized by introducing the Helmholtz and Gibbs energies
spontaneous process
is accompanied by a decrease in the Helmholtz energy at constant temperature and volume. is accompanied by a decrease in the Gibbs energy at constant temperature and pressure
maximum work
The change in the Helmholtz energy, obtainable from a system at constant temperature
maximum non-expansion work
The change in the Gibbs energy, obtainable from a system at constant temperature and pressure
standard Gibbs energies of formation
used to calculate the standard Gibbs energies of reactions
fundamental equation
a combination of the First and Second Laws, is an expression for the change in internal energy that accompanies changes in the volume and entropy of a system
Maxwell relations
a series of relations between partial derivatives of thermodynamic properties based on criteria for changes in the properties being exact differentials
thermodynamic equation of state
The Maxwell relations are used to derive the _______ to determine how the internal energy of a substance varies with volume.
temperature, pressure
The Gibbs energy of a substance decreases with _______ and increases with _______
Gibbs–Helmholtz equation
the variation of Gibbs energy with temperature is related to the enthalpy through this.
solids, liquids, gases
The Gibbs energies of _______ and _______ are almost independent of pressure; those of _______ vary linearly with the logarithm of the pressure
a form of matter that is uniform throughout in chemical composition and physical state
phase transition
the spontaneous conversion of one phase into another
the thermodynamic analysis of phases is based on the fact that at _______, the chemical potential of a substance is the same throughout a sample
phase diagram
indicates the values of the pressure and temperature at which a particular phase is most stable, or is in equilibrium with other phases
phase rule
relates the number of variables that may be changed while the phases of a system remain in mutual equilibrium
The chemical potential of a substance _______ with increasing temperature in proportion to its molar entropy
The chemical potential of a substance _______ with increasing pressure in proportion to its molar volume
The vapour pressure of a condensed phase _______ when pressure is applied
Clapeyron equation
an exact expression for the slope of a phase boundary
Clausius–Clapeyron equation
an approximate expression for the boundary between a condensed phase and its vapour