Liquids and Solids
Chapter 13
I. Comparison of Solids, Liquids and Gases
Solids
Shape
Molecular
Forces
Density
Compressibility
Fluidity
Rate of
Diffusion
Liquids
Gases
II. Changes of State
gas
deposition
most
energy
evaporation
sublimation
least
energy
condensation
moderate
energy
melting
solid
freezing
liquid
Question: Which phase changes ADD energy, and which
phase changes RELEASE energy?
III. Properties of Liquids
A. Surface Tension - pulling together of a liquids
SURFACE molecules, creating tighter arrangement
B. Vapor Pressure - the gaseous pressure resulting
from the vaporization of SURFACE molecules of
liquid
C. Boiling Point - the temperature at which a liquids
vapor pressure equals the atmospheric pressure
D. Viscosity – resistance to flow
Note: 1) Vaporization occurs at the SURFACE of liquids
2) Boiling occurs WITHIN, as well as the surface of a liquid
3) Boiling Point temperatures can be raised or lowered by a
corresponding change to the atmospheric pressure
Surface Tension
pulling together of a liquids SURFACE molecules, creating
tighter arrangement
Dipole-Dipole Interaction
Hydrogen Bonding
IV. Water and It’s Properties
A. Intermolecular hydrogen bonding is responsible
for the high boiling point of water:
O
H
H
note: the H-bondings
are additional bonds -weaker than covalent
bonds -- that must be
broken before boiling
can occur
O
H
H
O
H
O
H
H
H
B. When water freezes, the water molecules arrange
themselves into hexagonal patterns:
H
notes:
H
HO
1) the wider spacing between
HO
O
H
H
O
2) water is most dense at 4
oC… warmer and colder than
this causes expansion
H
O
H
OH
H
H
molecules causes ice to be
LESS DENSE than liquid water
H
3) the volume of the
hexagonal spaces in ice is
equal to the volume of ice that
is above the water line when
floating
C. Energy requirements for phase changes of water:
1) water requires 1 calorie (4.184 joules) to heat 1 gram
of water 1 oC.
2) ice requires 80 calories per gram (6.02 kJ/mol)to melt
without any temperature change
3) water requires 540 calories per gram (40.8 kJ/mol) to
boil without any temperature change
Ex: How many calories are required to melt 50 grams of
ice, heat it to 100 oC, then boil it?
V. Phase Diagrams
A. Conveniently shows the relationship between
temperature, pressure and the physical state of a
substance.
B. Water has the only phase diagram with a negative
slope to the solid/liquid boundary
1) as pressure increases on ice, it liquifies
2) higher pressures cause smaller volumes …
3) … for water, liquid has smaller volume than solid
C. Triple Point – when all 3 phases coexist
D. Critical Point – 1) temp at which gas can no longer
become liquid no matter what the pressure is
2) pressure required to produce liquefaction at the
critical temperature
Phase Diagram for Water
Phase Diagram for CO2
VI. Types of Solids
A. Crystalline Solids 1) ionic crystals - metal + nonmetal
ex: NaCl; Fe2O3
2) Covalent Network - covalently bonded atoms
or molecules forming a large crystal
ex: C (diamond); SiO2 (sand)
3) Metallic - metal atoms sharing valence eex: Fe; Cu;
4) Covalent Molecular - intermolecular forces
between covalent solids
ex: ice; frozen gases (dry ice), S8, P4, I2
B. Amorphous Solids - non regularly shaped solids
ex: plastics; glass