Chapter 9
Liquids and Solids
16.1 Intermolecular Forces
16.2 The Liquid State
16.3 An Introduction to Structures and Types of Solids
16.4 Structure and Bonding in Metals
16.5 Carbon and Silicon: Network Atomic Solids
16.6 Molecular Solids
16.7 Ionic Solids
16.8 Structures of Actual Ionic Solids
16.9 Lattice Defects
16.10 Vapor Pressure and Changes of State
16.11 Phase Diagrams
Intermolecular Forces: Why Condensed Phases Exist
• Intramolecular Forces
– Chemical bonds
• Strong
• Directional
• Short Range (relative)
• Intermolecular Forces
• Weaker than chemical bonds, usually much weaker
• Less directional than covalent bonds
• Longer range than covalent bonds
• Condensed Phases
– Solids and Liquids
– Intermolecular forces: attractions between molecules that are in close
proximity (i.e. in liquids and solids)
The boiling points of the covalent hydrides of elements in
Groups 4A, 5A, 6A, and 7A.
Intermolecular Interactions
(van der Waals forces, non-bonded
interactions)
1.
2.
3.
4.
5.
6.
Are all electrostatic in nature (Coulomb’ Law
rules).
Are not operable for a perfect gas (except for
short range repulsion).
Are the source of molecular adhesion and
cohesion in liquids.
Are the source of molecular adhesion and
cohesion in solids.
Are disrupted during boiling or evaporation.
Are between molecules, not within molecules
Intermolecular Interactions
(van der Waals forces)
1. Charge-Charge (Ion-Ion, example NaCl)
2. Ion-Dipole [example NaCl (aq)]
3. Dipole-Dipole (example acetone, water)
(includes H-bonding)
4. Dipole-Induced Dipole and ion-Induced dipole
[example benzene (aq)]
5. London Dispersive Forces
[fluctuating dipoles, example He (l), N2(l)]
6. Short Range Repulsion (helps prevent black
hole formation)
Types of Non-Bonded (Intermolecular) Attractions
Ion-Dipole Interactions
Types of Non-Bonded (Intermolecular) Attractions
Dipole-Dipole Interactions (1)
Types of Non-Bonded (Intermolecular) Attractions
Dipole-Dipole Interactions (2)
Hydrogen Bonding
(a non-bonding interaction, not really a bond)
a water molecule
Types of Non-Bonded (Intermolecular) Attractions
Ion-Induced Dipole
Argon Atom
Argon Atom
Types of Non-Bonded (Intermolecular) Attractions
London Dispersion
•
transient fluctuations of
electron distributions
Kinetic Theory of Liquids and Solids
• Intermolecular distances
– Solids: 3 X 10 -10 m = 0.3 nm = 3 Å
– Liquids: about 5 X 10 -10 m = 0.5 nm = 5 Å (not for water)
– Gases: about 30 X 10 -10 m = 3.0 nm = 30 Å (depends on pressure)
• Intramolecular distances about 0.15 nm = 1.5 Å
The Liquid State
• Characteristics of the Liquid State
– Low compressibility
– High density, relative to gases
– Surface tension
– Exhibit capillary action
• Cohesive forces
• Adhesive forces
– Viscosity
The Liquid State
• Characteristics of the Liquid State
– Low compressibility
– High density, relative to gases
– Surface tension
– Exhibit capillary action
• Cohesive forces
• Adhesive forces Viscosity describes a liquid’s
– Viscosity
internal resistance to flow
• water has a lower viscosity
• vegetable oil has higher
viscosity.
A molecule in the interior of a liquid is attracted to the
molecules surrounding it, whereas a molecule at the
surface of liquid is attracted only by molecules below it and
on each side of it.
Cohesive forces bind molecules of the same type together
Adhesive forces bind a substance to a surface
• Adhesive Forces and Capillary Action
X
X
X
X
X
X
X
x
Water’s adhesive forces > cohesive forces,
causing a concave meniscus.
An Introduction to Structures and Types of Solids
1. Crystalline Solids
–
–
Highly regular arrangement
“Lattice”: 3D arrangement, with unit cell structures
•
•
•
Simple cubic (Po metal)
Body-centered cubic (Ur metal)
Face-centered cubic (Au metal)
2. Amorphous Solids
–
–
–
Disordered structures
Non-crystalline
E.g., window glass
Three cubic unit cells and the corresponding
lattices.
Examples of three types of crystalline solids.
Atomic Solids
Ionic Solids
Molecular Solids
X-rays scattered from two different
atoms may reinforce (constructive interference) or
cancel (destructive interference) one another.
d = distance between atoms
λ = wavelength
Reflection of X rays
Bragg Equation
n λ = 2 d sin θ