Alsothegreatestamountofdisorder

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Unformatted text preview: (increase
in
temperature
due
to
the
local
heating).
 
 Note
that
a
ball
at
rest
on
the
ground
 has
its
molecules
moving
in
all
 directions.

For
the
ball
to
lift
itself
in
 the
air,
all
molecules
must
 synchronize
their
motion
in
the
 upward
direction.
Obviously,
this
 never
happens!!
Again,
we
see
that
in
this
particular
case,
the
direction
in
 which
the
process
occurs
spontaneously
is
the
one
that
leads
to
a
dispersal
 of
energy
in
a
more
disordered
fashion.
When
considering
the
direction
of
a
 spontaneous
process,
and
the
notion
of
disorder,
it
is
important
to
 Marand’s
Notes:
Chapter
3
‐
The
Second
Law
of
Thermodynamics
 96
 remember
that
what
matters,
is
not
just
the
system
but
the
system
+
 surroundings.
 
 The
new
thermodynamic
function,
which
is
introduced
to
provide
 information
as
to
the
direction
in
which
a
system
evolves,
is
called
the
 entropy.
Like
the
internal
energy,
the
entropy
is
an
extensive
state
 function,
which
we
will
denote
by
S.
 As
a
system
evolves
from
state
A
to
state
B,
its
entropy
may
change
 by
an
amount
Δ S,
which
can
only
be
calculated
following
a
reversible
path
 from
A
to
B.
In
the
case
where
the
real
process
from
A
to
B
is
not
 reversible,
then
a
reversible
path
has
to
be
imagined
that
leads
from
A
to
B.

 Since
S
is
a
state
function,
the
change
ΔS
=
SB
‐
SA
is
independent
of
the
 path
chosen.

However,
the
key
concept
to
remember
is
that
entropy
 changes
can
only
be
calculated
along
reversible
paths.
 The
definition
of
entropy
is
given
by:
 dS = δqrev ⇒ ΔS = T B δqrev 
 T A...
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This note was uploaded on 01/26/2014 for the course CHEM 3615 taught by Professor Aresker during the Spring '07 term at Virginia Tech.

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