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Homework chapter 9:
15, 19, 21, 25, 27, 29,31. 33. 35, 39. 51, 53
61, 63
Remember:
Hour exam Wed Nov 9
1
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High standard of living =
high consumption of energy per person
3
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Chapters 9 and 10: Thermodynamics
Thermodynamics: the conversion of energy amongst its various forms
(mechanical, chemical, electrical, etc.) and the relation
of these conversions to macroscopic variables (i.e.
temperature, pressure, and volume) .
Sadi Carnot
Josiah W. Gibbs
17961832
18391903
“Reflections on the motive power of heat,” 1824
5
Thermochemistry:
study of the energy evolved or absorbed in chemical
reactions and in physical transformations, such as
melting or boiling.
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View Full Document Internal energy of any system
Internal energy (E ): sum of the kinetic and potential energies of all the
“particles” in the system.
Change of Internal Energy during a process:
∆
E = q
+
w
gg
y
g
p
q
∆
E = Final energy of system after process, minus initial energy of system before
process.
Alternative Form of First Law of Thermodynamics
=
hange
ternal
nergy
∆
E = change
in
internal energy
q = heat
[+
if heat flows into system
, – if heat flows out of system
w = work
(+ if surroundings do work on system
, – if system does work on
urroundings)
surroundings)
6
Thermodynamic calculations on ideal gases
he simplest
nd most important system
onsider is a monatomic ideal gas
The simplest and most important system to consider is a monatomic ideal gas
Ideal gases obey the relation PV = nRT
And for one mole E = (KE)
vg mole
= (3/2)RT where
(KE)
vg mole
= average translational
avg, mole
avg, mole
energy of 1 mol of gas at a given T (in K)
note:
ideal gas E is not a function of container volume V or pressure P, as ideal gas law
ignores interactions between molecules
Thus, the only way to change KE of an ideal gas is to change T
nd the energy (heat) required to change KE f 1 mol of gas by T is:
ad
teeeg
y
(e
a
t
)e
que
dtocag
e
oo
o
g
a
s
b
y
s
Energy (heat) required = (3/2)R
∆
T
Molar Heat Capacity
the energy (heat) required to raise
the temperature of 1 mole by 1 K
7
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View Full Document Process involving change of temperature
eating a gas: Energy and Enthalpy
Heating a gas: Energy and Enthalpy
KE = (3/2)RT (per mole)
Æ
for a monatomic gas, KE = E
For an ideal gas, to change KE, temperature must be increased
E = (3/2)RT (per mole)
= (3/2)R
(per mole)
ust a substitution;
∆
E
(3/2)R
∆
T (per mole)
C
v
=(3/2)R
For a monatomic ideal gas,
Just a subst tut o ;
Not a comment
suggesting the
process need be at
onstant volume
∆
E = C
v
∆
T
or
C
v
(rather than C
P
) appears in the expression
constant volume
∆
E = nC
v
∆
T (n moles)
for
∆
E because, at constant V, all of the input
energy goes into increasing E (i.e. no PV work)
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This note was uploaded on 11/03/2011 for the course MATH 1090 taught by Professor Greenwood during the Spring '08 term at MIT.
 Spring '08
 greenwood
 Calculus

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