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Ideal gas
…has no volume and no mutual attraction.
Sometimes called a point mass.
Therefore a balloon inflates not because of the volume but because of the motion of the particles.
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2. 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.
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4. 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)
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5. Intermolecular Forces
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6. 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.
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7. London Dispersion Forces
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8. 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.
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9. Some Properties of a Liquid
Surface Tension: The resistance to an increase in its surface area (polar molecules).
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10. Some Properties of a Liquid
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11. Some Properties of a Liquid
Surface Tension: The resistance to an increase in its surface area (polar molecules).
Capillary Action: Spontaneous rising of a liquid in a narrow tube.
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12. Some Properties of a Liquid
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13. Some Properties of a Liquid
Surface Tension: The resistance to an increase in its surface area (polar molecules).
Capillary Action: Spontaneous rising of a liquid in a narrow tube.
Viscosity: Resistance to flow (molecules with large intermolecular forces).
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Types of Solids
Crystalline Solids: highly regular arrangement of their components [table salt (NaCl), pyrite (FeS2)].
Amorphous solids: considerable disorder in their structures (glass).
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15. 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.
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16. Representation of Components in a Crystalline Solid
Unit Cell: The smallest repeating unit of the lattice.
simple cubic
body-centered cubic
face-centered cubic
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17. Representation of Components in a Crystalline Solid
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Bragg Equation
Used for analysis of crystal structures.
n = 2d sin 
d = distance between atoms
n = an integer
 = wavelength of the x-rays
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19. Types of Crystalline Solids
Ionic Solid: contains ions at the points of the lattice that describe the structure of the solid (NaCl).
Molecular Solid: discrete covalently bonded molecules at each of its lattice points (sucrose, ice).
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20. Types of Crystalline Solids
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21. Types of Crystalline Solids
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Packing in Metals
Model: Packing uniform, hard spheres to best use available space. This is called closest packing. Each atom has 12 nearest neighbors.
hexagonal closest packed (“aba”)
cubic closest packed (“abc”)
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23. Bonding Models for Metals
Electron Sea Model: A regular array of metals in a “sea” of electrons.
Band (Molecular Orbital) Model: Electrons assumed to travel around metal crystal in MOs formed from valence atomic orbitals of metal atoms.
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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
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25. Metal Alloys (continued)
2. Interstitial Alloy: Interstices (holes) in closest packed metal structure are occupied by small atoms.
steel = iron + carbon
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26. Metal Alloys (continued)
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27. Metal Alloys (continued)
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.
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Network Solids
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29. 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
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Network Solids
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Semiconductors
A substance in which some electrons can cross the band gap.
Conductivity is enhanced by doping with group 3a or group 5a elements.
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33. 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.
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Vapor Pressure
The more electrons a substance has the more polarizable it is, and the greater are the dispersion forces.
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Vapor Pressure
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36. Melting Point
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
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Boiling Point
Constant temperature when added energy is used to vaporize the liquid.
vapor pressure of liquid = pressure of
surrounding atmosphere
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Phase Diagram
Represents phases 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).
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Phase Diagram
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Phase Diagram
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