Figure by MIT OCW.
160
150
140
120
110
100
90
80
70
60
50
40
30
20
20
10
0
Figure by MIT OCW.
40
50
60
o
Temperature ( C)
70
80
0
Cp (kcal mole-1 K-1)
Enthalpy (kcal mole-1)
130
Liquid
v
1.25
1.15
solid
1.05
~α solid
50
T (0C)
100
150
The specific volume v (cm3 g-1) of polyethylene versus temperature T. The thermal expansion
coefficient α is proportional to the slope dv/dT. At low temperature, polyethylene is a hard
crystalline plastic material. On melting at around 130 oC, the specific volume v increases sharply
and α is large.
Figure by MIT OCW.
O
τ = 1010yrs
103sec
10-12sec
Volume
Glass Transition
2
(
Gas
CHa _ C _ O
|
CH2CH _
)
n
id
qu
Li
Glass
Crystal
1
Tg
Tf
Tb
Temperature
The two general cooling paths by which an assembly of atoms can condense into the solid state. Route 1
is the path to the crystalline state; Route 2 is the rapid-quench path to the amorphous solid state.
Figure by MIT OCW.
6
α
o
4
2
α
0
0
h
0.
02
h
V
0.84
10
Specific Volume (cm3/gram)
0.85
(cm3/gram K)
POLYVINYLACETATE
1
Tg
0.83
260
T
300
Tg
(oK)
340
Volume-versus-temperature cooling curves for an organic material in the neighborhood
of the glass transition. V(T) is shown for two greatly different cooling rates, as is the coefficient
of thermal expansion α(T) is shown for the fast-cooling curve (0.02 hr). The break in V(T), and
the corresponding step in α(T), signal the occurrence of the liquid glass transition.
Figure by MIT OCW.
V/Vo
1.00
o
120 C
o
90 C
o
60 C
0.95
~(-κ)
0.90
0
400
800
p (bars)
1200
The relative volume V/Vo of hexadecane decreases with applied pressure
p (Vo is the volume of the material extrapolated to zero pressure). Compressibility
increases with temperature. Source: RA Orwoll and PJ Flory, J Am Chem Soc
89(1967), 6814-6822.
Figure by MIT OCW.
α (K-1)
1.6 x 10-3
0.8 x 10-3
CH3-CH2-CH2-CH2-CH3
0
O
H
H
0
50
T (oC)
100
Thermal expansion coefficients α measured at atmospheric pressure
of water (
), benzene (
), n-pentane (
), and
diethylether (
).
κ (Pa-1)
Figure by MIT OCW.
2.4 x 10-9
1.4 x 10-9
0.4 x 10-9
0
50
100
T (oC)
Compressibilities κ measured at atmospheric pressure for water
(
), benzene (
), n-pentane (
), and
diethylether (
).
Figure by MIT OCW.
Molar specific heat, J/
40
1
2
mol . K
35
35
30
Cp
25
Cv
25
3R
20
15
NaCl
10
Cp, Cv, J/mol .K
30
3R
Cv
20
15
Copper
10
5
5
0
Cp
0
200
400
600
Temperature, K
800
1000
Temperature variation of Cp and Cv of 12 mol of NaCl.
0
0
200
400
600
800
1000
1200
Temperature, K
Temperature variation of Cp and Cv of copper.