Chapter 10
Liquids and Solids
Intermolecular Forces
Forces between (rather than within) molecules.
 dipole-dipole attraction:
molecules with
dipoles orient themselves so that “+” and “”
ends of the dipoles are close to each other.
 hydrogen bonds: dipole-dipole attraction in
which hydrogen is bound to a highly
electronegative atom (F, O, N).
Figure 10.2. Dipole-Dipole Attractions
Figure 10.3. A Water Molecule
Figure 10.4. The Boiling Points of the Covalent Hydrides of
the Elements in Groups 4A, 5A, 6A, and 7A
London Dispersion Forces
 relatively weak forces that exist among
noble gas atoms and nonpolar molecules.
(Ar, C8H18)
 caused by instantaneous dipole, in which
electron distribution becomes asymmetrical.
 the ease with which electron “cloud” of an
atom can be distorted is called
polarizability.
Figure 10.5. London Dispersion Forces
Types of Solids
• Crystalline Solids: highly regular arrangement
of their components [table salt (NaCl), pyrite
(FeS2)]. Crystalline solid produces the beautiful
characteristic shapes of crystals.
• Amorphous solids: considerable disorder in
their structures (glass). Although glass is a solid,
a great deal of disorder exists in its structure.
Representation of Components in a
Crystalline Solid
Lattice: A 3-dimensional system of points
designating the centers of components (atoms,
ions, or molecules) that make up the substance.
Unit Cell: The smallest repeating unit of the
lattice.
• simple cubic
• body-centered cubic
• face-centered cubic
Figure 10.9. Three Cubic Unit Cells and the Corresponding Lattices
Types of Crystalline Solids
• Ionic Solid: contains ions at the points of the lattice
that describe the structure of the solid (NaCl). When
NaCl dissolves in water, Na+ and Cl- ions are
distributed throughout the resulting solution.
• Molecular Solid:
discrete covalently bonded
molecules at each of its lattice points (sucrose, ice).
Sugar is composed of neutral molecules that are
dispersed throughout the water when the solid
dissolves.
• Atomic Solid: Atoms at the lattice points that describe
the structure of the solid (graphite, diamond,
fullerenes).
Figure 10.12. Examples of Three Types of Crystalline Solids
Metal Alloys
Substances that have a mixture of elements and
metallic properties.
1. Substitutional Alloy: some metal atoms replaced
by others of similar size.
brass = Cu/Zn (one third Cu replaced by Zn)
2. Interstitial Alloy: Interstices (holes) in closest
packed metal structure are occupied by small
atoms.
steel = iron + carbon
3. Both types: Alloy steels contain a mix of
substitutional (carbon) and interstitial (Cr, Mo)
alloys.
Figure 10.21. Two Types of Alloys
Network Solids
Composed of strong directional covalent
bonds that are best viewed as a “giant
molecule”.
•
•
•
brittle
do not conduct heat or electricity
carbon, silicon-based
graphite, diamond, ceramics, glass
Figure 10.22. The Structures of Diamond and Graphite
Figure 10.26. The Structure of Quartz
Figure 10.27. Silicate Anions
Vapor Pressure
is the pressure of the vapor present at
equilibrium.
is determined principally by the size of the
intermolecular forces in the liquid.
increases significantly with temperature.
 Volatile liquids have high vapor pressures.
 Heat of vaporization (Hvap.): The energy
required to vaporize 1 mole of a liquid at a
pressure of 1 atm. Vaporization is an
endothermic process.
Figure 10.38. Behavior of a Liquid in a Closed Container
Figure 10.39. The Rates of Condensation and Evaporation
Melting Point
• Temperature at which the solid and liquid
states have the same vapor pressure under
conditions where the total pressure is 1
atmosphere.
• Molecules break loose from lattice points
and solid changes to liquid. (Temperature is
constant as melting occurs.)
vapor pressure of solid = vapor pressure of
liquid
Boiling Point
• The temperature at which the vapor pressure
of the liquid is exactly 1 atmosphere.
• Constant temperature when added energy is
used to vaporize the liquid.
vapor pressure of liquid = pressure of
surrounding atmosphere
Phase Diagram
• Represents phases of a substance as a function
of temperature and pressure.
• Critical temperature: temperature above which
the vapor can not be liquefied.
• Critical pressure: pressure required to liquefy
AT the critical temperature.
• Critical point: critical temperature and
pressure (for water, Tc = 374°C and 218 atm).
• Triple point: all three states of water are
present.
Figure 10.50. The Phase Diagram for Water