AP Chem Ch. 13: Bonding & Molecular Structure: Intermolecular Forces, Liquids, & Solids
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goveganplease on July 8, 2011
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39 terms
Math / Symbols | English |
|---|---|
 intermolecular forces | forces between molecules or between ions & molecules |
| ion-dipole attraction | can be evaluated based on the equation for attraction between charges, Force ∝ (n^+e)(n^-e)/d²; from this equation, we can see that attractive forces depend on: 1) the distance between the ion & the dipole: the closer the ion & dipole, the stronger the attraction; 2) charge on the ion: the higher the ion charge, the stronger the attraction; 3) the magnitude of the dipole: the greater the magniture of the dipole, the stronger the attraction |
| solvation energy/enthalpy of hydration | energy associated w/ hydration of ions; cannot be measured directly, but values can be estimated |
| dipole-dipole attractions | attractions between dipoles in molecules |
| hydrogen bonding | cause high boiling points in H₂O, HF, & NH₃; special type of dipole-dipole interaction involving polar H-X bonds |
| dispersion forces; induced dipoles | found in all molecular substances; electronic in nature & arise from attractions involving ____; explain how some nonpolar molecules like iodine (I₂) can form solids @ room temperature or how they can dissolve in water or ethanol |
| biological oxygen demand (BOD) | quantity of oxygen required to oxidize given quantity of organic material; highly polluted water often has high concentration of organic matter & so has high _____ |
| polarization | process of inducing dipole |
| polarizability | degree to which electron cloud of atom (e.g. Ne or Ar) or molecules (e.g. O₂, N₂; or I₂) can be distorted to induce dipole depends on _____; valence electrons of atoms or molecules w/ large, extended electron clouds, such as I₂, can be polarized, or distorted, more readily than the electrons in a much smaller atom or molecule, such as He or H₂, in which the valence electrons are close to the nucleus & more tightly held; in general, for an analogous series of compounds, say the halogens or alkanes, the higher the molar mass the greater the _____ of the molecule |
| evaporation/vaporization | process in which substance in liquid state becomes gas; molecules escape from liquid surface & enter gaseous state |
| molar enthalpy of vaporization | ∆H°(subscript vap); how heat energy required to vaporize sample given; Liquid (vaporization)/(heat energy absorbed by liquid) --> Vapor |
| condensation | a molecule in the gas phase will eventually transfer some of its kinetic energy by colliding slower gaseous molecules & solid objects; if this molecule comes in contact w/ the surface of the liquid again, it can reenter the liquid phase in a process called ____; Vapor (condensation/heat energy released by vapor) --> Liquid |
| dynamic equilibrium | for example, when water is put in a sealed flask and the rate of vaporization equals the rate of condensation; represented using set of double arrows connecting reactant & product or 2 phases of substance |
| equilibrium vapor pressure | pressure exerted by water vapor, often called vapor pressure; measure of tendency of its molecules to escape fom liquid phase & enter vapor phase @ given temp |
| volatility | tendency of molecules to escape from liquid phase & enter vapor phase @ given temp; if the equilibrium vapor pressure is high, then the ____ of the compound will be high |
| Clausius-Clapeyron equation | developed by German physicist R. Clausius (1822 - 1888) & Frenchman B.P.E. Clapeyron (1799 - 1864) in 19th cent; lnP = -(∆H[subscript vap]/RT) + C, where ln P is the natural logarithm of the vapor pressure, T is the Kelvin temperature at which P is measured, ∆H(subscript vap) is the enthalpy of vaporization of the liquid, R is the ideal gas constant, and C is a constant characteristic of the compound in question; provides method of obtaining values for ∆H(subscript vap) |
| normal boiling point | (of a liquid) temperature at which vapor pressure is equal to external pressure when the external pressure is 1 atm; direct relationship between ____, enthalpy of vaporization, & intermolecular forces |
| critical point | the temperature and pressure at which the interface between liquid & vapor disappears |
| critical temperature | T(subscript c); the temperature at which the critical point is reached |
| critical pressure | P(subscript c); the pressure at which the critical point is reached |
| supercritical fluid | substance that exists under critical temperature and critical pressure; like a gas under such a high pressure that its density resembles a liquid's, while its viscosity (ability to flow) remains close to that of a gas |
| surface tension | energy required to break through surface or to disrupt liquid drop & spread material out as film; causes water drops to be spheres and not litte cubes, for example b/c sphere has smaller surface area than any other shape of same volume |
| capillary action | closely related to surface tension; when a small-diameter glass tube is placed in water, the water rises in the tube, just as water rises in a piece of paper in water; because there are polar Si-O bonds on the surface of the glass, polar molecules are attracted by adhesive forces between the 2 different substance; these forces are strong enough that they can compete with the cohesive forces between the water molecules themselves; thus, some water molecules can adhere to walls, & others are attracted to these & build a "bridge" back into the liquid; the surface tension of the water (from cohesive forces) is great enough to pull the liquid up the tube, so the water level rises in the tube; the rise will continue until the various attractive forces - adhesion between water & glass, cohesion between water molecules - are balanced by the force of gravity on the water column; these forces lead to the characteristic concave, or downward-curving, meniscus that you see for water in a drinking glass or in a lab test tube |
| viscosity | resistance of liquids to flow |
| unit cell | (for a crystalline solid) the smallest repeating unit that has all of the symmetry characteristic of the way atoms, ions, or molecules are arranged |
| ionic solids | positive & negative ions; no discrete molecules; ionic forces holding units together; attractions among charges on positive & negative ions; hard; brittle; high melting point; poor electric conductivity as solid, good as liquid; often water-soluble |
| metallic | i.e.: iron, silver, sopper, other metals & alloys; metal atoms (or positive metal ions surrounded by electron sea); metallic forces holding units together; electrostatic attraction among metal ions & electrons; malleable; ductile; good electric conductivity in solid & liquid; good heat conductivity; wide range of hardness & melting points |
| molecular | molecules held together by covalent bonds; forces holding units together: dispersion forces, dipole-dipole forces, hydrogen bonds; low to moderate melting points & boiling points; soft; poor electric conductivity in solid & liquid |
| network | graphite, diamond, quartz, feldspars, mica, elemental silicon is a _____ solid w/ a diamond-like structure & silicon dioxide, SiO₂ is also a ____ solid atoms held in an infinite one-, two-, or three-dimensional network; forces holding units together: covalent; directional electron-pair bonds; wide range of hardness & melting points (3-D bonding >2-D bonding > 1-D bonding b/c great deal of energy must be provided to break covalent bonds in lattice); poor electric conductivity, w/ some exceptions |
| amorphous (glassy) | glass, polyethylene, nylon; covalently bonded networks w/ no long-range regularity ∴ not possible to identify unit cell in the solid phase; like liquids, but forces of attraction are strong enough that movement of molecules is restricted; forces holding units together: covalent; directional electron-pair bonds; noncrystalline; wide temperature range for melting; poor electric conductivity, w/ some exceptions |
| lattice points | corners of cube or other geometric object that constitutes unit cell; the ____ defining each unit cell in simple solids represent identical environments for the ions in an ionic solid, metal atoms in a metallic solid, or molecules in a molecular solid |
| crystal lattice | defined by lattice points; nature uses 7, 3-D unit cells; these differ from one another in that their sides have different relative lengths & their edges meet @ different angles & one of these lattices is differentiated from others by being hexagonal |
| cubic unit cell | simplest of 7 crystal lattices; cell w/ edges of equal length that meet @ 90 degree angles |
| primitive or simple cubic/ body-center cubic/face-centered | sc/bcc/fcc; all 3 have 8 identical atoms or ions @ corners of cubic unit cell; bcc & fcc fragments differ from sc because have additional particles, of same type as those @ corners, @ other locations; bcc structure is called "body centered" b/c has additional particles @ center or "body" of cube; fcc arrangement called "face-centered" b/c has, in center of each of 6 faces of cube, a particle of the same type as the corner atoms; metals may assume any of these structures - alkali metals, for example, are bcc, whereas nickel, copper, & aluminum are fcc |
| octahedral holes | in NaCl, each Na⁺ ion is surrounded by 6 Cl⁻ ions; an octahedral geometry is assumed by the ions surrounding an Na⁺ ion so the Na⁺ ions are said to be ______ |
| silicates | compounds composed of silicon & oxygen; sand, quartz, talc, & mica, major constituent of rocks such as granite |
| enthalpy of fusion | energy required to melt, or the energy required to cause the lattice to collapse; heat energy absorbed on melting = enthalpy of fusion = ∆H(subscript fusion) *(kJ/mol) Heat energy evolved on freezing = Enthalpy of crystallization = -∆H(subscript fusion) (kJ/mol) |
| phase diagram | used to illustrate relationship between phases of matter & pressure & temperature; lines identify conditions under which 2 phases exist @ equilibrium (all points that don't fall on lines in figure represent conditions under which 1 state exists) |
| triple point | characterized by conditions under which all 3 phases can coexist in equilibrium; for water, the triple point is at P = 4.58 mm Hg & T = 0.01 degrees C |
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