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Unformatted text preview: E‘H’r____M_ (MAL MM 14 P
ﬂ—Fﬁl MM —Nb.zq CHAPTER 11. v
INTERMOLECULAR FORCES, LIQUIDS AND SOLIDS. (Preparing us for materials chemistry)
When intermolecular forces are large enough,
temperatures low enough, or pressures high enough
(provided T is below the critical temperature) liquids
form in preference to gases. The density, in moles/1 of
the typical liquid is of order 1000-2000 times greater
than that of an ambient pressure gas. The volume of a liquid changes with temperature in a manner quite distinct from that of a gas i.e.
Charles' law is completely wrong in the rate of expansion that it would predict. However liquids do
expand linearly V = const x T, and we use this property to measure temperature (mercury thread
thermometer) Gases turn into liquids through a process of "condensation", like dewdrops. Inversely liquids turn
into gases by (slow) evaporation, or (fast) boiling. Intermolecular forces. (a) Van der Waals forces (London Dispersion forces, or
uctuatin di ole forces
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“(C-0'; ..5 $3 0 IV (b) Dipole- -dipole forces (Permanent dipoles) O 09 q- .. 4. a.“ Cult. 0M 0?
H F" " H F A F
cf 6 N cc.
H’o- " o on o ‘ . ‘ ‘ ‘
(d) ion-dipole forces "K Q““*"""S '- l-t ro‘l-I
H 6“ +lv+ "uhﬁ‘ LEM—o H 'F «‘4
H3 * J. tumu- 1h»;
(e) ion-ion forces (e. g. liquid NaCl, currently “ionic liquids” what are these?) TM > ? 0 0 o. L— (g) covalent bonding forces (liquid silicon) M‘H
that moo K , c. git-not K Relative strengths. . .see Fig. 11—? The larger strength the more endothermic is
the bOiliIlg pI'OCCSS. Boilingaliquid metalisn’teasy! ...
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- Fall '08