Chapter 12

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Chapter 12
2012-07-01 15:47:55

Gen Chem II
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  1. intermolecular forces
    forces between independent particles
  2. polar molecule
    one in which one portion of the molecule is more negatively charged than another part of the same molecule; it's net charge is 0, but its assymetrical charge distribution causes it to interact with nearby ions or other polar species
  3. polarizability
    the tendency of a nonpolar molecule to become an induced dipole; the more weakly held electrons are, the MORE polarizable the particle is
  4. heavy items tend to be ____ polarizable
    more; atomic mass/number increases because there are more electrons, and if there are more electrons there is more shielding
  5. mass and BP vary:
    conversly; as mass increases so does polarizability and therefore so does BP; it becomes more difficult to seperate particles
  6. as temperature increases, average kinetic energy ___________ as well
    increases; faster moving partices can overcome attractions more easily
  7. condensation; opposite of _______
    the process by which a gas changes into a liquid; it's the opposite of vaporization
  8. vaporization; opposite of __________
    the process by which a liquid changes into a gas; it's the opposite of condensation
  9. freezing; opposite of _________
    the process by which a liquid changes into a solid; opposite of melting/fusion
  10. melting/fusion; opposite of _________
    the process by which a solid 'melts' into a liquid; opposite of freezing
  11. heat of vaporization (ΔHvap)
    the amount of energy required to transform a given quantity of a substance from a liquid into a gas at a given pressure
  12. heat of fusion (ΔHfus)
    the amount of energy required to transform a given quantity of a substance from a liquid into a solid at a given pressure
  13. sublimination
    when a solid becomes a gas without first transforming into a liquid; opposite of deposition; ΔHsubl = the sum of the heats of fusion and vaporization
  14. deposition
    when a gas becomes a solid without first becoming a liquid; opposite of sublimination
  15. molar heat capacity (C)
    the amount of heat required to change a substance's temperature by a given amount (measured in J/K, joules per Kelvin)
  16. exothermic reaction
    a chemical reaction that releases energy in the form of light or heat; gas → liquid → solid (a solid's particles are closer together/don't move as much B/C there's been a lot of heat released/that phase doesn't require a lot of 'heat'/energy to exist)
  17. endothermic reaction
    a chemical reaction in which a system absorbs energy from the surroundings in the form of heat; solid → liquid → gas (for any substance to transform into a gas, it needs to absorb a lot of heat [think of it like the temperature increases] because gaseous molecules move FAST and are very energetic)
  18. the higher the temperature, the ______ the vapor pressure
  19. the weaker the intermolecular forces are, the ______ the vapor pressure
  20. vapor pressure
    is an indication of a liquid's evaporation rate; it relates to the tendency of particles to escape from the liquid, so if vapor pressure is high, the substance will vaporize more easily and quicker
  21. Kelvin to Celcius
    • Celcius = ___K - 273.15
    • Kelvin = ___C + 273.15
  22. C-C equation
    • can find vapor pressure if given temperature, or temperature if given vapor pressure!
    • ln(P2/P1) = -ΔHvap/R (1/T2 - 1/T1)
    • aka natural log of the 2nd pressure divided by the first set equal to REVERSE SIGN of the heat of vaporization divided by gas constant multiplied by temp. 2 minus temp. 1)
  23. boiling point
    the temperature at which the vapor pressure equals the external pressure (usually that of the atmosphere)
  24. surface tension
    the energy required to increase the surface atrea by a unit amount [J/m2]; property of the surface of a liquid that allows it to resist an external force
  25. the stronger the forces are between the particles of a liquid, the _______ the surface tension
    greater (higher); ex. mercury has a a very high surface tension because of Metallic bonding
  26. viscosity
    a liquid's resistance to flow; stronger forces result in higher viscocity (so it's proportional to forces; weaker forces result in weaker viscocity)
  27. viscocity _________ with heating
    DECREASES; so as temperature increases, liquids flow more (have lower viscocity)
  28. go back and read page
  29. lattice
    consists of all points with identical surroundings
  30. unit cell
    the smallest portion of the crystal, that if repeated in all three directions, gives the crystal
  31. coordination number
    the coordination number of a central atom in crystal is the number of its nearest neighbours
  32. simple cubic unit cell
    • coordination # is 6; the number of atoms per unit cell = 1, P.E. = 52%, a=2r
  33. body-centered cubic unit cell
    • coordination # is 8; the number of atoms per unit cell = 2, P.E. = 68%, a=4r/√3
  34. face-centered cubic
    • coordination # is 12; the number of atoms per unit cell = 4, P.E.=74%, a=√8(r)
  35. for particles of equal size, the higher the coordination number of the crystal is, the _______ the number of particles in any given volume
  36. atomic mass
    mass of 1 atom/atomic mass unit
  37. packing efficiency
    the percentage of total volume occupied by the spheres (atoms) in a given space themselves; so a high percentage means they're packaged efficienty/close together
  38. hexagonal closest packing
    (which is based on the hexagonal cell unit) is when the third layer of spheres lies directly ABOVE the 1st (a) layer, resulting in an abab... pattern; PE = 74%
  39. cubic closest packing
    is when the third layer of spheres lies directly above the SPACES in the 1st (a) layer, resulting in an abcabc... pattern (based on face-centered cubic unit cell); PE = 74%
  41. atomic solid
    individual atoms held together by dispersion forces; only examples are when noble gasses occur when noble gases are cooled to really low temperatures and lock themselves in place using very weak London dispersion forces (don't occur in “real world” b/c you need temperatures that are too low to see them)
  42. Molecular solids
    occur when covalent molecules are held together by intermolecular forces; intermolecular forces between the molecules are strong enough to keep the molecules locked into place; typically, these solids (ex. ice) have a lower melting/boiling points than metallic, network atomic, or ionic solids, b/c intermolecular forces are much weaker than those of the bonds in the other compounds
  43. Ionic solids
    very stable solids in which anions & cations stick together via “electrostatic attraction” (opposite charges like to stick together); they require lots of energy to pull apart
  44. Metallic solids
    solids in which the positively charged nuclei are held together by a bunch of valence electrons; these electrons are referred to as “delocalized” b/c they travel throughout the solid; this causes atoms in solid to move around along with their electrons; around with them (“electron sea theory” describes positive metal nuclei as floating around in an ocean of negative electrons that hold them together); metald do this kind of bonding
  45. Network covalent solids
    big crystals in which all of the atoms are stuck together using covalent bonds; b/c atoms are stuck in place these solids usually have properties very similar to ionic compounds (high melting and boiling point, hard, brittle, etc); the exception is that they don’t conduct electricity if melted; ex: gemstones
  46. amorphous solids
    have no particular crystal structure; particles are 'stuck' all over with no regular bonding pattern; some are soft and rubbery (ex: plastic & rubber) because they consist of long tangled molecules bound by intermolecular forces; others called glassy solids are more like network atomic solids because they consist of atoms stuck together in an irregular fashion using covalent bonds