Chapter 3 Flashcards
A spontaneous change occurs
___________ continuous input of
energy into the system from
outside
without
A nonspontaneous process
requires_________ input of
energy
constant
Spontaneous in one direction
means ____________ in
opposite direction
non-spontaneous
_______________ processes involve ordered motion becoming
random and localized energy becoming dispersed
Spontaneous (Non-spontaneous processes involve the reverse)
Thus, dispersal of matter and energy tends to be
______________ while the concentration of matter
and energy tends to be non-spontaneous
spontaneous
Second Law of Thermodynamics
Heat does not flow spontaneously
from a cool body to a hotter body
The Second Law can be expressed in terms of a new state function, _____________
entropy
The entropy of an isolated system __________ in the course of a spontaneous change: ΞStot > 0
increases
Thermodynamically irreversible changes always have ______________
ΞStot > 0
define entropy in thermodynamics
according to the what equation?
ππ = πππππ£/T & βπ = Χ¬π
π πππππ£/T
In some processes, ΞSsys is negative (energy or matter is getting concentrated, not dispersing) but can still be spontaneous if _______________
spontaneously if ΞSsur is sufficiently positive that ΞStot > 0
What are some examples of spontaneous processes where ΞSsys is positive?
Gas expanding
β Water evaporating
What are some examples of spontaneous processes where ΞSsys is negative?
-Water condensing on a cold glass
β Water freezing from a liquid to a solid in the freeze
So, πππππ£/π is essentially the _______________ value for the change in entropy for a process; it could be more
minimum
units of entropy are
what?
J/K
Entropy is an ____________ property, so amount of entropy depends on system size
extensive
What is the equation used for entropy and the surrounding?
βππ π’π = ππ π’π/ T sur
we generally assume that the
surroundings are held at a __________ temperature and either constant volume or constant pressure
constant
what is βππ π’π for an adiabatic
process?
βππ π’π = 0
In statistical mechanics, entropy is defined via the Boltzmann equation as what?
π = π ln π² & π = π ln Ξ© (where π² or Ξ© represent the number of microstates possessed by a state with a given internal energy. k is
the Boltzmann constant: k = 1.380649Γ10β23 Jβ
Kβ)
microstate
snapshot of a state at the molecular level
A microstate is described by the individual positions and ________________ of every atom
velocities
There are generally huge numbers of ____________ microstates β microstates with the same values of the macroscopic variables P, V, T, and n
equivalent
Less constrained systems (like gases) have ________ equivalent microstates
more
More constrained systems (like solids) have _______ equivalent microstates
fewer
An analogy to states and microstates using _______
dice (The state is the sum of the values on the dice
β The microstate is the specific set of values rolled)
The Carnot Cycle involves ______ steps and is an idealized representation of an engine that produces work from heat
4
To calculate the entropy change associated with a given process (expansion, phase transition,
heating, etc.), find a _________ path between initial and final state.
reversible
Equation for Isothermal expansion of an ideal gas (of the system)
βπ = ππ
ln ππ/Vi (If process is reversible, βππ π¦π = ββππ π’π
β In that case, βππ‘ππ‘= βππ π¦π + βππ π’π=0)
(However, if expansion is against a fixed pressure,
βππ‘ππ‘β 0
β Specifically, if it is free expansion (against a vacuum),
βππ π’π= 0, so βππ‘ππ‘ = ππ
ln π)
In physical chemistry, a change in physical state (solidβliquid; liquidβgas) is usually called a
________________
phase transition
To analyze a phase transition, we limit ourselves to consider the process at the normal _________________
transition temperature, Ttr (At this temperature, the 2 phases are in equilibrium
β Thus, the process is reversible in either direction)
If π = βπ‘ππ π» is the heat involved in the phase transition, we can easily find ΞS with what equation?
βπ‘ππ π = βπ‘ππ π»/ Ttrs
However, in exothermic processes, because βπ‘ππ π <0, βππ π’π must be ____________
positive
For endothermic processes, heat is entering the system, so _______
βπ‘ππ π > 0
Heat leaving the surroundings means ____________
βππ π’π< 0
If both system and surroundings are at Ttrs, they
are in equilibrium and βππ π’π= _______
-βπ‘ππ π
Nernst Heat Theorem
The entropy change accompanying any physical or chemical transformation approaches zero as
the temperature approaches 0: ΞSβ0 as Tβ0 provided all the substances involved are perfectly
ordered
Third law of entropy
The entropy of all perfect crystalline substances is zero at T=0 K
The entropy of a pure substance in its standard state is called its __________ βThird-Lawβ entropy
or just its standard entropy
standard
Generally, reactions that result in a net increase in gas will have ___________ βπππ, while reactions that result in a net decrease in gas will have negative βπππ
positive
With ___________ equation, we now have expressions for conditions for spontaneous processes that only
include properties of the system
Helmholtz
The change in Helmholtz energy is equal to the ___________ work that can accompany a process at
constant temperature
maximum
If a reaction has ΞG < 0, it is ____________
spontaneous
If a reaction has ΞG > 0, the __________ reaction is spontaneous
reverse
A system at equilibrium has ΞG = ?
Zero
