Liquids and Solids
Characteristics of Liquids and
Solids
• What properties allow you to classify a
substance as a solid, liquid, or gas?
Property
Volume
Shape
Relative density
Compressibility
Fluid?
Space between
particles
Diffusion rate
Motion of particles
(amount and type)
Forces between
particles?
Solid
Liquid
Gas
Surface Tension
• Surface tension is
the tendency for
liquid surface to
contract.
• Depends on IMFs
• Compounds that
interfere with the
IMFs and reduce
surface tension are
called surfactants.
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
Figure 12.19
Shape of water or mercury meniscus in glass.
capillarity
stronger
cohesive forces
adhesive forces
H 2O
Hg
Figure 12.4
Liquid-gas equilibrium.
Vapor Pressure
Vapor pressure = the pressure
of the vapor resulting from
evaporation of a liquid (or solid)
above a sample of the liquid (or
solid) in a closed container
What factors affect the vapor
pressure?
Figure 12.6
Vapor pressure as a function of
temperature and intermolecular forces.
Boiling Point
• Temperature at which the vapor
pressure of the liquid = atmospheric
pressure
• Normal boiling point
vpliquid = 760 mmHg
• condensing point = boiling point
What if…?
• You are camping at a high altitude of
10,000 ft where the atmospheric
pressure is 535 mmHg. If you boil an
egg for 10 minutes will it be hard-boiled
just right, overdone, or runny? Explain
your choice.
Subliming Point
• Temperature at which the vapor
pressure of the solid equals atmospheric
pressure
• Depositing point = subliming point
Iodine subliming
Figure 12.12
Dipole moment and boiling point.
Figure 12.13
Hydrogen bonding and boiling point.
Figure 12.16
Molecular shape and boiling point.
fewer points for
dispersion
forces to act
more points for
dispersion
forces to act
Freezing Point
• Temperature at which liquid and solid
are in equilibrium
• Not affected by pressure but does
depend on IMFs and molar mass
• Melting point = freezing point
Figure 12.21
The hexagonal structure of ice.
Figure 12.22
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
portion of a 2-D lattice
Figure 12.27
Diffraction of x-rays by crystal planes.
Table 12.5
Particles
Atomic
Atoms
Molecular Molecules
Characteristics of the Major Types of Crystalline Solids
Interparticle
Forces
Physical
Behavior
Dispersion
Soft, very low mp, poor
thermal & electrical
conductors
Dispersion,
Fairly soft, low to moderate
dipole-dipole, H mp, poor thermal & electrical
bonds
conductors
Examples (mp,0C)
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