rreve Revers
b
i
le/l rs i b le
TODAY'S LECTLIRE:
"Spontaneity, Entropy
and Free Energy"
B
Processes
Reversible Process: a system is changed in
such a way that the system AND surroundings
are restored to their original state by exactly
reversing the change
(Chapter 10)
TEST CASE: Isothermal Expansion and Compression
1) Expansion and Compression
of
an Ideal Gas
of an Ideal
Isothermal: temperature of system and surroundings
Gas
remain constant at all times
2) Reversible and Irreversible Processes
Heat reseNoir
r)
Since:
LE:
q
+x:0
=@
4) Calculating AS for Physical Processes
mss
P..,.",= force
areQ
"One-Step" Expansion and
Gompression
:llExpansion)
,t | ----\
Ej Zfr*'*il
\r-A
lWorkl
I Step
W
-->
-ir,
Net nork
@
=
Pa+
UJ
guml
Net heat flow =
-li)
= - ?t \tlr+V,
,ein
-v,6ltV1
- \()T ltE\ llRslBLII
t>
1/=
1L
Steps
area under graph (pink)
=
=
Reduce P"*,: P, -+ P,14
Work
- -}.l1Ptvl
lr,lt
=
vt
M, wf -+ Mrl4
Reduce pressure in 2 steps
2\
4/,
6 Steps
Compressionz P1l4 -+ P1 and 4V, -+
-
j Pu,",,"rocnrassinpan
\aea ofpiston
Extra work done
4Vt
v'- -P,,,LV = - (erc( vJ. -v D -- -lt+,,-v,>
=1
:
1
: PLV:
11 volume
l-step Expansion followed by l-step Compression
v' = - P".,,LL'
.Vs
Expalsion,
ra-)1
2)
Acceleratlon due to gravity
Reduce mass:
Nt
Expansion: P, -+ Prl4 and Vt
\/
Multiple-Step Expansion Work
--:----v G
\i,n,
l)
constdt T)
=AE:0
Entropy and Work
,- -)
(+
lr,l
Expansion work is
pathway-dependent
Work is not a state function
Even more
) hV1
V,'4
ead, sV =
-- >-YgYrV
L z/t
XA
ffi/
{#M
6
workdone
lwul=\r,ur,
t=l
J
:t&L/tffiWz7l)
lr,lr....]r,1r l.,l
W
Infinite steps
Infinite small steps in external
pressure between P, and Prl4
-)
-)
maximum area
maximum work
(done to surroundings)
tv)=o 9 -
--v0
->'tPrv1 C lw't dea'sedS
+