Title: States of Matter: Liquids and Solids
1States of Matter Liquids and Solids
2Changes of State
Phase Transition Name Solid Liquid Melting/Fus
ion Solid Gas Sublimation Liquid
Solid Freezing Liquid Gas Vaporization Gas
Liquid Condensation Gas Solid Condensation
3Vapor Pressure and ??vap
- The heat involved in vaporizing a liquid is the
enthalpy of vaporization.
?Hvap
log (Pvap) - (1/T) C
2.303R
Pvap is the vapor pressure ?Hvap is the heat of
vaporization C is a constant
4Determining ??vap
- A Plot of the vapor pressure vs. 1/T yields ??vap
Pvap
Ether
H2O
1/T
5Determining ??vap
- A Plot of the vapor pressure vs. 1/T yields ??vap
Pvap
Ether
H2O
1/T
?Hvap
Pvap1
log ( - )
1 T2
1 T1
Pvap2
2.303R
6Heat of Fusion
- The heat necessary to melt one mole of a solid.
- ?Hfus
7A Question of Energy
- What parameters do you need to calculate the
energy necessary to raise the temperature of
water from -20 oC to 120 oC? - g H2O, Cwater, Cice, Csteam, b.p. of water, m.p.
of water, ?Hfus, ?Hvap
8Boiling Point
- The boiling point is the point at which the vapor
pressure equals the pressure exerted on the
liquid. - Pvap Psys
9Vapor Pressure Example
- Chloroform, CHCl3, a volatile liquid, was once
used as an anesthetic but has been replaced by
safer compounds. It boils at 61.7oC and has a
heat of vaporization of 31.4 kJ/mol. What is its
vapor pressure at 25.0oC?
10Vapor Pressure of CHCl3 at 25 oC
- At the normal boiling point, the vapor pressure
of a liquid is 760.0 mmHg. Use the
Clausius-Clapeyron equation to find P2 when P1
760.0 mmHg, T1 334.8 K, and T2 298.1 K.
11Vapor pressure of CHCl3 at 25.0oC?
- P1 760.0 mmHg, T1 334.8 K, T2 298.1 K
??vap 31.4 kJ/mol
??vap
(T2 - T1)
P2
_____
______
___
Log
x
P1
2.303 R
T2T1
12Vapor Pressure of CHCl3 at 25 oC
- P1 760.0 mmHg, T1 334.8 K, T2 298.1 K
??vap 31.4 kJ/mol
??vap
(T2 - T1)
P2
_____
______
___
Log
x
P1
2.303 R
T2T1
31.4 x 103 J/mol
(298.1 - 334.8 K)
________________
_______________
x
(298.1K)(334.8 K)
(2.303)8.31 J/(K.mol)
13Vapor Pressure of CHCl3 at 25 oC
P2
__
Log
-0.6033
P1
log P2 log P1 - 0.6033 log (760.0) - 0.6033
2.27751
P2 antilog (2.27751) 189.4 189 mmHg
14Phase Diagrams
- A plot of temperature vs. pressure has discrete
phase regions.
liquid
Critical Point
solid
P
Triple Point
gas
T
15Intermolecular Forces
- Dipole-Dipole Forces
- Electrostatic interactions between polarized
molecules - Hydrogen Bonding
- Same as Dipole-Dipole, but involve H?-O?-
- London-Dispersion Forces
- Interactions of instantaneous dipoles
- Metallic Bonding
16Two Types of Solids
- Crystals are . . .
- well-defined arrangements of atoms, ions, or
molecules. - Amorphous Solids are . . .
- solids with no long-range molecular order.
17What Is a Unit Cell?
- The smallest repeating unit that contains the
characteristics of the crystal as a whole.
18Crystal Lattice
- The 3-D array of points which represents an
identical environment within the crystal.
193 Kinds of Cubic Unit Cells
- Primitive Cubic
- Body-centered Cubic
- Face-centered Cubic
20Fraction of an Atom at Various Positions in the
Unit Cell
Position
Fraction
Center Face Edge Corner
1 1/2 1/4 1/8
21Example
- Find the density (g/cm3) for ??Fe.
- BCC (Body-centered Cubic)
- a 2.86
- Fe 55.85 g/mole
- N 6.02 x 1023 atoms/mole
A
22Example
- Find the density (g/cm3) for ??Fe.
- Solution
- Volume of Unit Cell (2.86 A )3 x (1 cm/108 A
)3 - 2.34 x 10-23 cm3
23Example
- Find the density (g/cm3) for ??Fe.
- Solution
Volume of Unit Cell (2.86 )3 x (1 cm/108
)3 2.34 x 10-23 cm3 mass/unit cell
55.85g/mole x 2 atoms 6.02 x
1023 atoms/mole 1.86 x 10-22 g
A
A
24Example
- Find the density (g/cm3) for ??Fe.
- Solution
Volume of Unit Cell (2.86 )3 x (1 cm/108
)3 2.34 x 10-23 cm3 mass/unit cell
55.85g/mole x 2 atoms 6.02 x
1023 atoms/mole 1.86 x 10-22 g Density
Mass/Volume 7.93 g/cm3
A
A
25Atomic Mass of Iron
- Metallic iron has a body-centered cubic lattice
with all atoms at lattice points and a unit cell
whose edge length is 2.866 A. The density of
iron is 7.87 g/cm3. What is the mass of an iron
atom? Compare this value with the value you
obtain from the molar mass.
26Atomic Mass of Iron
- Calculate the volume of the unit cell, change
density to g/m3, and then convert volume to mass,
using density - Volume (2.866 x 10-10m3) 2.354 x 20-29m3
27Atomic Mass of Iron
- Calculate the volume of the unit cell, change
density to g/m3, and then convert volume to mass,
using density - Volume (2.866 x 10-10m3) 2.354 x 20-29m3
3
7.87 g
102cm
x
7.87 x 106 g/m3
cm3
m
28Atomic Mass of Iron
- Calculate the volume of the unit cell, change
density to g/m3, and then convert volume to mass,
using density - Volume (2.866 x 10-10m3) 2.354 x 20-29m3
3
7.87 g
102cm
x
7.87 x 106 g/m3
cm3
m
Mass of one cell
(7.87 x 106 g/m3) x (2.354 x 10-29 m 3)
1.8526 x 10-22 g
29Atomic Mass of Iron
- Because Fe is a body-centered cubic cell, there
are two Fe atoms in the cell, and . .
. Mass of one Fe atom (1.8526 x 10-22g)
x 2 9.263 x 10-23 g
30Atomic Mass of Iron
- Because Fe is a body-centered cubic cell, there
are two Fe atoms in the cell, and . .
. Mass of one Fe atom (1.8526 x 10-22g)
x 2 9.263 x 10-23 g
Using the molar mass to calculate the mass of
one Fe atom, you find the agreement is good
55.85 g Fe
1 mol Fe
x
1 mol Fe
6.022 x 1023 Fe atoms
9.274 x 10-23 g/Fe atom
31Close Packing of Spheres
- Ions and molecules can be viewed as spheres.
- Efficient packing maximizes attractive forces.
322 Types of Closest Packing
- Hexagonal Closest Packed (HCP)
- ABAB
- Hexagonal
- Cubic Closest Packed (CCP)
- ABCABC
- Face-centered Cubic
33Coordination Number (CN)
- The number of particles immediately surrounding
a particle in the crystal structure. - CN Number of nearest numbers
34Lattice Defects
- Disorder During Packing
- Point Defects
- Missing particles form Schottky defects
- May still maintain electrostatic neutrality
- Frenkel Defects
- Particles in the wrong position
35A Question of Distance
- How can we rationalize the different distances in
each of the following cases?
Solid Atomic Distance Molecule Distance
P4 S8 Cl2
2.20 2.06 1.99
3.8 3.7 3.6
36Molecular Solids
- Intermolecular Forces
- Dispersion forces, dipole-dipole forces,
H-bonding - Properties
- Soft, low melting point, poor thermal and
electrical conductivity - Examples
- H2O, CO2
37Covalent/Network Solids
- Covalent bonds
- Properties
- Very hard, very high melting point, poor thermal
and electrical conductivity - Examples
- C(diamond), SiO2(quartz)
38Ionic Solids
- Electrostatic attractions
- Highly dependent on the charge of the ions
- Properties
- Hard brittle, high melting point, poor thermal
and electrical conductivity - Examples
- NaCl, CaCO3
39X-ray Diffraction
- X-rays will be diffracted by an array of atoms in
an ordered solid. The diffraction is due to
scattering of X-rays by the atoms.
40X-ray Diffraction
- X-rays will be diffracted by an array of atoms in
an ordered solid. The diffraction is due to
scattering of X-rays by the atoms.
Bragg Equation
n? 2dsin?