Chapter 12
Intermolecular Forces:
Liquids, Solids, and Phase Changes
12-1
12.1 물리적 상태와 상 변화의
개관
12.2 상 변화의 양적 측면
상 변화에 수반되는 열
상 변화의 평형 성질
상 그림
12.3 분자간 힘의 형태
이온－쌍극자 힘
쌍극자－쌍극자 힘
수소 결합
전하－유발쌍극자 힘
분산력(런던 힘)
12.4 액체의 성질
12-2
표면장력
모세관 현상
점성
12.5 물의 독특한 성질
용매 성질
열 성질
표면 성질
고체 물 및 액체 물의 밀도
12.6 고체 상태: 구조, 성질 및
결합
고체의 구조적 특성
결정성 고체
비결정성 고체
고체의 결합
ATTRACTIVE FORCES
electrostatic in nature
Intramolecular forces
bonding forces
These forces exist within each molecule.
They influence the chemical properties of the substance.
Intermolecular forces nonbonding forces
These forces exist between molecules.
They influence the physical properties of the substance.
12-3
상변화
sublimination
melting
gas
vaporizing
liquid
solid
freezing
12-4
condensing
Table 12.1
A Macroscopic Comparison of Gases, Liquids, and Solids
State
Shape and Volume
Compressibility Ability to Flow
Gas
Conforms to shape and volume
of container
high
high
Liquid
Conforms to shape of container;
volume limited by surface
very low
moderate
Solid
Maintains its own shape and
volume
almost none
almost none
12-5
증발열 및 융해열
12-6
Figure 12.2
12-7
Phase changes and their enthalpy changes.
기체 내 입자들은 멀리 떨어져 무작위하게 움직이고 있고,
액체 내 입자들은 서로 접하고는 있으나 상대적으로 서로 움직이고 있고,
고체 내 입자들은 서로 접하고 경직된 구조에서 위치가 고정되어 있다.
이는 분자간 힘과 운동에너지의 상대적 크기에 기인한다.
물질의 각 상태에 따른 형태, 압축률, 유동성 등 거시적 차이는 분자수준에서 차이가
있기 때문이다.
고체, 액체, 기체로 변하는 과정에서 에너지가 흡수된다.
주어진 조건하에서일어나는 각 상 변화에는 이에 해당하는 엔탈피 변화가 수반된다.
10-8
Figure 12.3
A cooling curve for the conversion of gaseous water to ice.
12-9
Quantitative Aspects of Phase Changes
Within a phase, a change in heat is accompanied by a change in
temperature which is associated with a change in average Ek as
the most probable speed of the molecules changes.
q = (amount)(molar heat capacity)(T)
During a phase change, a change in heat occurs at a constant
temperature, which is associated with a change in Ep, as the
average distance between molecules changes.
q = (amount)(enthalpy of phase change)
12-10
Figure 12.4
12-11
Liquid-gas equilibrium.
Figure 12.5
12-12
액체 내 분자들의 속력분포와 온도
Figure 12.6
Vapor pressure as a function of
temperature and intermolecular forces.
12-13
Figure 12.7
A linear plot of vapor
pressure- temperature
relationship.
The Clausius-Clapeyron Equation
ln P =
-Hvap1 
   C
R
T 
P2
-Hvap 1
1 
ln
=
  
R T2 T 
P1
1
12-14
Using the Clausius-Clapeyron Equation
34.9℃에서 에탄올의 증기압은 115torr이다. 에탄올의 ΔH증발은
40.5kJ/mol이다. 증기압이 760torr인 온도(℃)를 계산하라.
주어진 것들 ΔH증발, P1, P2, T1을 식 12.1에 대입하고 T2에 대해 푼다. 여기서
R 값은 8.31 J/mol·K이므로 T1을 K 단위로 바꾸어 T2를 구한 다음 T2를 다시
℃로 바꾼다.
SOLUTION:
P2
-Hvap  1 1 
ln
=
  
P1
R T2 T1
760 torr
ln
115 torr
=
-40.5 x103 J/mol
8.314 J/mol*K
T2 = 350K = 770C
12-15
34.90C = 308.0K
1
1
T2
308K
Figure 12.8
Phase diagrams(상도표)
CO2
12-16
H 2O
Figure 12.9
Covalent and van der Waals radii.
van der Waal’s distance
bond length
covalent radius
van der Waal’s radius
12-17
Figure 12.10
Periodic trends in covalent and van der Waals radii (in pm).
12-18
모형
이온
인력의 근원
에너지(kJ/mol)
보기
양이온－음이온
400∼4000
NaCl
150∼1100
H-H
75∼1000
Fe
공유
핵－공유된
전자쌍
금속
양이온－비편재
전자들
12-19
모형
이온
인력의 근원
에너지(kJ/mol)
보기
양이온－음이온
400∼4000
NaCl
150∼1100
H-H
75∼1000
Fe
공유
핵－공유된
전자쌍
금속
양이온－비편재
전자들
12-20
인력의 근원
에너지
(kJ/mol)
이온－쌍
극자
이온전하－쌍극자
전하
40∼600
H－결합
극성결합－H쌍극자
전하 (N, O, F의
높은 전기음성도)
10~40
쌍극자－
쌍극자
쌍극자 전하들
5~25
이온－유
도
쌍극자
이온전하－편극된
전자구름
3~15
힘
모형
쌍극자－
유도
쌍극자
쌍극자 전하－
편극된 전자구름
분산력
(런던 힘)
편극된
전자구름들
12-21
2~10
0.05∼40
보기
Figure 12.11
극성 분자들과 쌍극자－쌍극자 힘.
solid
liquid
12-22
THE HYDROGEN BOND
a dipole-dipole intermolecular force
A hydrogen bond may occur when an H atom in a molecule,
bound to small highly electronegative atom with lone pairs of
electrons, is attracted to the lone pairs in another molecule.
The elements which are so electronegative are N, O, and F.
H
hydrogen bond
acceptor
..
O
..
O
..
..
..
..
F
..
hydrogen bond
donor
hydrogen bond
acceptor
hydrogen bond
acceptor
12-23
H
..
..
N
..
F
..
hydrogen bond
donor
H
..
N
hydrogen bond
donor
Figure 12.12
12-24
쌍극자 모멘트와 끓는점
SAMPLE PROBLEM 12.2
PROBLEM:
Which of the following substances exhibits H bonding? For
those that do, draw two molecules of the substance with the H
bonds between them.
O
C2H6
(a)
PLAN:
(c)
CH3C NH2
(a) C2H6 has no H bonding sites.
H
H C O H
H
H
H O C H
H
12-25
(b) CH3OH
Find molecules in which H is bonded to N, O or F. Draw H
bonds in the format -B:
H-A-.
SOLUTION:
(b)
Drawing Hydrogen Bonds Between Molecules
of a Substance
H
(c)
H
O
H N CH3C CH C
3
N H
O
CH3C N H
H N
CH3C
O
H
H
O
Figure 12.13
12-26
수소 결합과 끓는점
Polarizability and Charged-Induced Dipole Forces
distortion of an electron cloud
•Polarizability increases down a group
size increases and the larger electron clouds are further
from the nucleus
•Polarizability decreases left to right across a period
increasing Zeff shrinks atomic size and holds the electrons
more tightly
•Cations are less polarizable than their parent atom
because they are smaller.
•Anions are more polarizable than their parent atom
because they are larger.
12-27
Figure 12.14
Dispersion forces among nonpolar molecules.
separated
Cl2
molecules
12-28
instantaneous
dipoles
Figure 12.15
Molar mass and boiling point.
12-29
Figure 12.16
Molecular shape and boiling point.
fewer points for
dispersion
forces to act
more points for
dispersion
forces to act
12-30
SAMPLE PROBLEM 12.3
PROBLEM:
Predicting the Type and Relative Strength of
Intermolecular Forces
For each pair of substances, identify the dominant
intermolecular forces in each substance, and select the
substance with the higher boiling point.
(a) MgCl2 or PCl3
(b) CH3NH2 or CH3F
(c) CH3OH or CH3CH2OH
PLAN:
CH3
(d) Hexane (CH3CH2CH2CH2CH2CH3)
CH3CCH2CH3
or 2,2-dimethylbutane
CH3
Use the formula, structure and Table 2.2 (button).
•Bonding forces are stronger than nonbonding(intermolecular) forces.
•Hydrogen bonding is a strong type of dipole-dipole force.
•Dispersion forces are decisive when the difference is molar mass or
molecular shape.
12-31
SAMPLE PROBLEM 12.3
Predicting the Type and Relative Strength of
Intermolecular Forces
continued
SOLUTION:
(a) Mg2+ and Cl- are held together by ionic bonds while PCl3 is covalently
bonded and the molecules are held together by dipole-dipole interactions. Ionic
bonds are stronger than dipole interactions and so MgCl2 has the higher boiling
point.
(b) CH3NH2 and CH3F are both covalent compounds and have bonds which are
polar. The dipole in CH3NH2 can H bond while that in CH3F cannot. Therefore
CH3NH2 has the stronger interactions and the higher boiling point.
(c) Both CH3OH and CH3CH2OH can H bond but CH3CH2OH has more CH for
more dispersion force interaction. Therefore CH3CH2OH has the higher boiling
point.
(d) Hexane and 2,2-dimethylbutane are both nonpolar with only dispersion
forces to hold the molecules together. Hexane has the larger surface area,
thereby the greater dispersion forces and the higher boiling point.
12-32
Figure 12.17
Summary diagram for analyzing the intermolecular forces in a sample.
INTERACTING PARTICLES
(atoms, molecules, ions)
ions present
ions only
IONIC BONDING
(Section 9.2)
ions not present
polar molecules only
DIPOLE-DIPOLE
FORCES
ion + polar molecule
ION-DIPOLE FORCES
nonpolar
molecules only
DISPERSION
FORCES only
H bonded to
N, O, or F
HYDROGEN
BONDING
polar + nonpolar
molecules
DIPOLEINDUCED DIPOLE
FORCES
DISPERSION FORCES ALSO PRESENT
12-33
Figure 12.18
The molecular basis of surface tension.
hydrogen bonding
occurs across the surface
and below the surface
the net vector
for attractive
forces is downward
hydrogen bonding
occurs in three
dimensions
12-34
Table 12.3
표면장력과 입자들 간의 힘
Surface Tension
Substance
Formula
(J/m2) at 200C
diethyl ether
CH3CH2OCH2CH3
1.7x10-2
dipole-dipole; dispersion
ethanol
CH3CH2OH
2.3x10-2
H bonding
butanol
CH3CH2CH2CH2OH
2.5x10-2
H bonding; dispersion
H2O
7.3x10-2
H bonding
Hg
48x10-2
metallic bonding
water
mercury
12-35
Major Force(s)
Figure 12.19
Shape of water or mercury meniscus in glass.
capillarity
stronger
cohesive forces
adhesive forces
H 2O
12-36
Hg
Table 12.4 Viscosity of Water (물의 점성도)
viscosity - resistance to flow
Temperature(0C)
Viscosity
(N*s/m2)*
20
1.00x10-3
40
0.65x10-3
60
0.47x10-3
80
0.35x10-3
*The units of viscosity are newton-seconds per square meter.
12-37
Figure 12.20
The H-bonding ability of the water molecule.
hydrogen bond donor
hydrogen bond acceptor
12-38
The Unique Nature of Water
•great solvent properties due to polarity and
hydrogen bonding ability
•exceptional high specific heat capacity
•high surface tension and capillarity
•density differences of liquid and solid states
12-39
Figure 12.21
12-40
The hexagonal structure of ice.
Figure 12.22
12-41
The striking beauty of crystalline solids.
Figure 12.23
The crystal lattice and the unit cell.
lattice point
unit
cell
unit
cell
portion of a 3-D lattice
12-42
portion of a 2-D lattice
Figure 12.24 (1 of 3)
The three cubic unit cells.
단순입방
1/8 atom at
8 corners
Atoms/unit cell = 1/8 * 8 = 1
배위수 = 6
12-43
Figure 12.24 (2 of 3)
The three cubic unit cells.
체심입방
1/8 atom at
8 corners
1 atom at
center
Atoms/unit cell = (1/8*8) + 1 = 2
배위수= 8
12-44
Figure 12.24 (3 of 3)
The three cubic unit cells.
면심입방
1/8 atom at
8 corners
1/2 atom at
6 faces
배위수 = 12
12-45
Atoms/unit cell = (1/8*8)+(1/2*6) = 4
Figure 12.26
Packing of spheres.
simple cubic
(52% packing efficiency)
body-centered cubic
(68% packing efficiency)
12-46
Figure 12.26 (continued)
layer a
layer b
hexagonal
closest
packing
layer a
cubic closest
packing
layer c
closest packing of first
and second layers
abab… (74%)
hexagonal
unit cell
12-47
expanded
side views
abcabc… (74%)
face-centered
unit cell
SAMPLE PROBLEM 12.4 Determining Atomic Radius from Crystal Structure
PROBLEM:
PLAN:
Barium is the largest nonradioactive alkaline earth metal. It has
a body-centered cubic unit cell and a density of 3.62 g/cm3.
What is the atomic radius of barium?
(Volume of a sphere: V = 4/3pr3)
We can use the density and molar mass to find the volume of 1 mol of
Ba. Since 68%(for a body-centered cubic) of the unit cell contains
atomic material, dividing by Avogadro’s number will give us the volume
of one atom of Ba. Using the volume of a sphere, the radius can be
calculated.
density of Ba (g/cm3)
radius of a Ba atom
reciprocal divided by M
volume of 1 mol Ba metal
V = 4/3pr3
volume of 1 Ba atom
multiply by packing efficiency
volume of 1 mol Ba atoms
12-48
divide by Avogadro’s number
SAMPLE PROBLEM 12.4 Determining Atomic Radius from Crystal Structure
continued
SOLUTION:
Volume of Ba metal =
37.9 cm3/mol Ba
26 cm3
mol Ba atoms
r3
x
3.62 g
x 0.68
x
137.3 g Ba
mol Ba
= 37.9 cm3/mol Ba
= 26 cm3/mol Ba atoms
mol Ba atoms
6.022x1023 atoms
= 4.3x10-23 cm3/atom
-23
3
3V
3(4.3x10
cm
) = 2.2 x 10-8cm
r =3
3
4p
4 x 3.14
= 3V/4p

12-49
1 cm3
Figure 12.27
Diffraction of x-rays by crystal planes.
12-50
Figure 12.28
Formation of an x-ray diffraction pattern of the
protein hemoglobin.
12-51
Figure 12.29
Cubic closest packing for
frozen argon.
12-52
Figure 12.30
Cubic closest packing
of frozen methane.
Table 12.5
Particles
Atomic
Atoms
Molecular Molecules
Characteristics of the Major Types of Crystalline Solids
Interparticle
Forces
Dispersion
Dispersion,
dipole-dipole,
H bonds
Physical
Behavior
Examples (mp,0C)
Soft, very low mp, poor
thermal & electrical
conductors
Fairly soft, low to moderate
mp, poor thermal &
electrical conductors
Group 8A(18)
[Ne-249 to Rn-71]
Nonpolar - O2[-219],
C4H10[-138], Cl2
[-101], C6H14[-95]
Polar - SO2[-73],
CHCl3[-64], HNO3[42], H2O[0.0]
Ionic
Positive & Ion-ion
negative ions attraction
Hard & brittle, high mp,
good thermal & electrical
conductors when molten
NaCl [801]
CaF2 [1423]
MgO [2852]
Metallic
Atoms
Metallic bond
Soft to hard, low to very
high mp, excellent thermal
and electrical conductors,
malleable and ductile
Na [97.8]
Zn [420]
Fe [1535]
Network
Atoms
Covalent bond Very hard, very high mp,
usually poor thermal and
electrical conductors
12-53
Figure 12.31
The sodium chloride structure.
expanded view
12-54
space-filling
Figure 12.32
cubic closest packing
12-55
Crystal structures of metals.
hexagonal closest packing
12-56
Figure 12.33
12-57
Crystalline and amorphous silicon dioxide.
Figure 12.35
12-58
The band of molecular orbitals in lithium metal.
Figure 12.36
Electrical conductivity in a conductor, semiconductor, and insulator.
conductor
insulator
semiconductor
12-59
Figure 12.37
The levitating power of a superconducting oxide.
rare earth magnet
superconducting ceramic disk
liquid nitrogen
12-60
결정성 고체 내 입자들은 반복되는 단위세포들로 이루어진 구조를 형성하는 점들에
놓여 있다. 입방계 단위세포들의 세 가지 유형으로는 단순, 체심, 면심이 있다. 가장
효 율 적 인 쌓임 배 열 은 입 방 조 밀쌓 임 및 육 방 조 밀쌓 임 이다 . 결 정 구 조 내
결합길이와 결합각은 X선 회절해석으로 결정할 수 있다. 원자 고체들은 조밀쌓임
구조를 가지며 원자들은 아주 약한 분산력으로 붙들려 있다. 분자 고체 내 분자들은
흔히 입방 조밀쌓임 구조의 격자점에 있다. 이들의 분자간힘 (분산력,
쌍극자－쌍극자 힘, 수소 결합) 및 물리적 성질들은 광범위하게 변한다. 이온
고체들은 한 가지 이온들로 이루어진 입방 조밀쌓임 구조에 생긴 구멍들을 다른
이온들이 메워 생성된다. 이 고체들의 녹는점과 경도가 높고, 전기 전도도가 낮은
것은 이온들 간의 인력이 세기 때문이다. 대부분의 금속들은 조밀쌓임 구조를
가진다. 그물구조 공유고체의 원자들은 시료 전체에 걸쳐 공유결합되어 있다.
비정형 고체들은 입자들 간에 규칙성이 거의 없다. 전자 바다 모형에 따르면 금속은
고도로 비편재화된 원자가 전자들로 이루어진 전자“바다”에 잠겨 있는 양이온들
로 되어 있다. 이 전자들은 시료 내 모든 원자들에게 공유된다. 띠 이론에 따르면
고체 내 원자들은 서로 결합하여 분자궤도함수들의 연속체, 즉 띠를 형성한다.
금속은 전자들이 이 에너지 연속체의 채워져 있는 영역(원자가띠)에서 비어있는
영역(전도띠)로 자유롭게 이동할 수 있기 때문에 전기를 통한다. 절연체에서는 이 두
영역들 간의 에너지 간격이 넓고, 반도체에서는 간격이 좁다.
10-61