CHAPTER 14 – LIQUIDS AND SOLIDS
LIQUIDS
Attractive forces hold molecules close together, although molecules can
still roll around
6B-1 (of 32)
Solid
Liquid
Gas
Vibrating
Rolling
Straight-Line
PHASE CHANGES
(1) EVAPORATION
If surface molecules acquire enough kinetic
energy to overcome the attractive forces,
they can escape
With liquid water in a closed container:
(2) CONDENSATION
Vapor molecules collide with the surface of
the liquid, lose energy, and are captured
When these 2 processes are equal, it looks like evaporation has stopped
Really, evaporation and condensation are occurring at equal rates
6B-2
DYNAMIC EQUILIBRIUM – When 2 opposing processes in the same
system proceed at equal rates
Evaporation:
liquid → vapor
Condensation:
vapor → liquid
Equilibrium:
liquid ↔ vapor
EQUILIBRIUM VAPOR PRESSURE – The pressure exerted by a vapor
when it is in equilibrium with its liquid
6B-3
EVP depends on temperature
Temp (ºC)
EVP (torr)
10
9
20
30
6B-4
18
32
BOILING
Atmospheric Pressure
A bubble is full of steam that exerts water’s
EVP
A bubble survives when its EVP equals
atmospheric pressure
When bubbles can reach the top the liquid is
boiling
BOILING POINT – The temperature at which the EVP of the liquid equals
the prevailing atmospheric pressure
6B-5
Temp (ºC)
5
10
20
30
95
100
122
6B-6
EVP (torr)
7
9
18
32
634
760
1557
HEATING CURVES
All pure substances can exist as solid, liquid, or gas
NORMAL MELTING POINT – At 1 atm pressure, the temperature a solid
turns into a liquid (also called the NORMAL FREEZING POINT)
NORMAL BOILING POINT – At 1 atm pressure, the temperature a liquid
turns into a gas
6B-7
HEAT OF FUSION – The heat needed to melt a specific amount of a solid
For ice:
334 J/g
or 6.02 kJ/mol
HEAT OF VAPORIOZATION – The heat needed to boil a specific amount
of a liquid
For water:
6B-8
2,250 J/g or 40.6 kJ/mol
Calculate the heat energy needed to change 10.00 g of ice at 0.0ºC to
steam at 100.0ºC.
Melting:
Liquid:
Boiling:
(334 J/g)(10.00 g)
= 3,340 J
(4.184 J/gCº)(10.00 g)(100.0 Cº) = 4,184 J
(2,250 J/g)(10.00 g)
= 22,500 J
30,024 J = 30,000 J
6B-9
SUBLIMATION – A solid changing directly to a gas
Iodine (I2), Dry Ice (CO2), Mothballs (C10H8)
DEPOSITION – A gas changing directly to a solid
6B-10
SOLIDS
CRYSTALLINE SOLID – A solid with a definite particle arrangement
AMORPHOUS SOLID – A solid with a random particle arrangement
Sand
Crystalline
6B-11
Glass
Amorphous
MELTING POINTS OF SOLIDS
Melting points (and boiling points) depend on the attractive forces
BETWEEN particles (molecules, atoms, or ions)
TYPES OF SOLIDS
(1) Molecular
(A) Nonpolar
(B) Polar
(2) Atomic
(A) Nonmetallic Network
(B) Metallic Network
(3) Ionic
6B-12
(1) MOLECULAR SOLIDS
INTRAMOLECULAR FORCES – Forces
WITHIN a molecule
Covalent bonds
They determine how reactive a molecule is
INTERMOLECULAR FORCES – Forces
BETWEEN molecules
They determine melting points and boiling
points
Intramolecular Forces
Intermolecular Forces
6B-13
There are two types of molecular solids
(A) NONPOLAR MOLECULAR
Made of individual nonpolar molecules
Examples: O2, CO2 (linear)
6B-14
Intermolecular Forces:
LONDON DISPERSION FORCES
(or VAN DER WAALS FORCES) –
The attraction of electrons in one
molecule to the nuclei in a neighboring
molecule due to the synchronizing of
electrons
δ+
δ-
δ+
δ-
LDF’s are weak attractive forces, so nonpolar molecular solids have low
melting points
LDF’s Increase in strength as the number of electrons per molecule increase
6B-15
Although they are composed of atoms, Noble Gases behave as nonpolar
molecular matter
6B-16
(B) POLAR MOLECULAR
Made of individual polar molecules
Examples: HCl, SO2 (bent)
6B-17
Intermolecular Forces:
London Dispersion Forces, and
DIPOLE-DIPOLE ATTRACTIONS –
The attraction of the positive end of
one polar molecule to the negative
end of another
δδ+
δ+
δ-
D-D Attractions are weak, so polar molecular solids have low melting
points
D-D Attractions are stronger than LDF’s, so polar molecular solids have
higher melting points than nonpolar molecular solids
6B-18
Polar molecules that have a H bonded to either N, O, or F have a third type
of attractive force
HYDROGEN BONDING – An intermolecular attraction between a H in one
molecule and a N, O, or F in a neighboring molecule
Hydrogen
Bonding
Polar molecules that can H-Bond have higher melting points than polar
molecular that cannot
6B-19
H-Bonding:
Causes ice to be less dense than water
by forming an open crystal lattice
produces the folded shapes of proteins
holds together the strands of DNA
molecules
6B-20
(2) ATOMIC SOLIDS
There are two types of atomic solids
(A) NONMETALLIC NETWORK
Made of millions of nonmetal atoms
Examples: Cx (diamond), (SiO2)x (sand)
Attractive forces:
Covalent bonds
6B-21
All atoms are covalently bonded together, so the entire crystal is like one
giant molecule
Covalent Bonds are strong, so nonmetallic networks have high melting
points
6B-22
(B) METALLIC NETWORK
Made of millions of metal atoms
Examples: Fe, Au, bronze (Cu + Sn), brass (Cu + Zn)
Attractive forces:
Metallic Bonds
6B-23
METALLIC BONDS – The attraction between metal nuclei and the valence
electrons of the millions of atoms
Metallic Bonds are strong, so metallic networks have high melting points
6B-24
ALLOY – A solid solution of metals
SUBSTITUTIONAL ALLOY
Brass
6B-25
INTERSTITIAL ALLOY
Steel
(3) IONIC SOLIDS
Made of millions of positive and negative ions
Examples: NaCl, CuSO4
Attractive forces:
Ionic Bonds
6B-26
+
- +
+ - +
-
Ionic Bonds are strong, so ionic substances have high melting points
6B-27
Substance
MP (ºC)
Substance Type
Attractive Forces
H2
O2
Ar
-259
-218
-189
Nonpolar Molecular
“
“
LDF
“
“
HCl
HBr
-114
-89
Polar Molecular
“
LDF, D-D
“
NH3
H2O
-78
0
“
“
LDF, D-D, H-B
“
NaCl
MgF2
801
1266
Ionic
“
Ionic Bonds
“
Fe
W
1535
3410
Metallic Network
“
Metallic Bonds
“
(SiO2)x
Cx
1723
3550
Nonmetallic Network
“
Covalent Bonds
“
6B-28
ELECTRICAL CONDUCTION
ELECTRICIAL CONDUCTION – The movement of charges particles
(electrons or ions) through a material
Conductors:
Metallic networks
Electrons can move throughout the metallic bonds
Nonconductors:
Molecular solids or Nonmetallic networks
Electrons are locked in covalent bonds
Ionic solids
Ions are locked in position as a solid,
BUT melted or dissolved in water, the ions can move and the
ionic material conducts
6B-30
REVIEW FOR TEST
Pressure (mm Hg, torr, atm)
Temperature (ºC, K)
Standard Temperature and Pressure (STP)
Boyle’s Law, Charles’ Law, Avogadro’s Law
Char-Boyled Law
Ideal Gas Law
Partial Pressure
Water Vapor Pressure
Pressure of Gases Collected in Lab
Over Mercury
Over Water
Gas Volumes in Chemical Reactions
6B-31
REVIEW FOR TEST
Dynamic Equilibrium
Melting, Boiling, Sublimation
Heat of Fusion, Heat of Vaporization, Specific Heat Capacity
Heating Curves, Heat Calculations
Crystalline, Amorphous Solids
Intramolecular Forces, Intermolecular Forces
London Dispersion Forces, Dipole-Dipole Interactions, Hydrogen Bonding
Attractive Forces, MP’s, Conductivity of
Molecular Solids (Nonpolar Molecular and Polar Molecular)
Atomic Solids (Nonmetallic Networks and Metallic Networks)
Ionic Solids
Alloys (Substitutional, Interstitial)
6B-32