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Phase change related to: intermolecular forces + KE
Chemical behavior in diff phases - samePhysical behavior in diff phases - diffWHY????? Due to strength of inter- forces
PE depends on (Coulomb’s) *charges of particles; dist bet
**KEspeed absol. T
FORCESIntra-F: w/i the molecule
Inter-F: bet molecules
POINTSmost all liquids @ room temp are molecules
Intra-F give rise to covalent bonding influence 1) molecular shape 2) bond E’s 3) chem behavior
Ch.8attraction of gases deviates Ideal Gas Law
PHYSICAL PROPERTIES OF LIQUIDS - SOLIDS
Due to inter-F
show table 11.1 pg 444
Characteristic Properties of G - L - S understood in terms of …. 1) E of motion (KE) of 2) particles (atoms, molecules, ions) of 3) g-l-s statescompared to E of inter-F bet particle
GASE of attraction bet particles <<< KEave
>allows gas to expand
LIQUIDS >Inter-F liquid > in gases >hold particles together >denser, less compressible than gases >partilces move among others, allows “pouring”
SOLIDS >Inter-F >>> gases/liquids >“lock”particles in rigid form* E & motion >little free space >Crystalline: orderly structured arrangement
Free Space: gas > liquid > solid
condensed phase
Then how canyou state?
heating or cooling; KE
show fig 11.2 pg 445show how the molecules are arrangedamong themselves in diff phases
N2O (decr temp) room: gas -88.5oC: melts, liq -90.8oC: solid
Bonding Ionic --- Covalent --- Metallic
Forces vary for diff subst Inter-F < Ionic < Covalent
E to vaporize liqE to evaporate liq E to melt solid
INTERMOLECULAR FORCES
< E break covalent bond
show fig 11.3 pg 446431 kJ required to break H - Cl bond16 kJ required to separate 2 HCl molecules
Notice: as states, molecules remain intact
show fig 11.2 pg 445
Forces Influence
1) BP weak inter-F, lowers2) MP stronger inter-F, raises
Van der Waals Forces >bet neutral molecules
Viscosityresistancce to flow, inter- attraction slow liq movement incr T -- decr viscosity stronger inter- > higher viscdepends on: T & shape of molecule larger molecules higher visc long shape higher visc than small round shape (thnk of contact)
3 Types Intermolecular Forcesbet neutral molecules1) Dipole-Dipole*2) London Dispersion*3) Hydrogen BondingSolutionsIon-Dipole *Van der Waals Forces
electrostaticmuch weaker than covalent/ionic
+ -+ -
Involves cations - anionsIon attracted to polar moleculeex. NaCl in H2O
attraction incr as 1) ion charge incr 2) dipole moment incr
ION - DIPOLE
Na+1
OH
H OH H
O
H H
OH
H
OH H
O
H H
O
H H O H
H
Cl-1
O
H H
similar to ion, but bet neutral charge polar molecules;+/- ends of polar molecule attract
D-D < I-D
DIPOLE - DIPOLE
+ -
+ -+ - + -
+ -
diff molecules of approx = size & mass: attraction incr w/ incr polarity, BP incr
Polar vs Non higher bp
More E to overcomeforces -- higher bp
show fig 11.7 pg 448
Which subst has the strongest dipole-dipole attraction?
fig. 11.8 pg.449
>only force bet NP molecules - no dipole moment
>molecules w/ NO permanent polarity caused by momentary movement of e- charge in atoms are present bet all particles
DISPERSION (LONDON) FORCES
Then how can anonpolar gas, N2,
be liquified?
Must be sometype of attraction!
NONPOLARoverall: equal distr of e- charge - polarity cancels (average)
actual: e- movement at any moment causes e- density to be conen at one end creating instantaneous dipole.Not permanent will change
Ar ........
Ar........ Ar ....
....+
+-
-
special Dip-Dip when H bonded to small size, high EN atom w/ unbonded e- pairplays imprt role in biological sys
Criteriamolecule 1: H bonded to O, N, or Fmolecule 2: unbonded e- on O, N, or F
result: H on molecule 1 interact w/ unbonded e- on molecule 2
H2O - H2O NH3 - CH2FCl
H - BONDINGH - BONDING
O
H H
O
H H..
..
....
ClF C H H
......
......
H N H H
..
HF - HBr CH3CH(OH)CH3 - CH3CH(OH)CH3
H - BONDINGH - BONDING
..H--F .... H--Br
..
..
..? CH3 CH CH3
O-H
.... CH3 CH CH3
O-H
....
CH3Br -- CH3F
CH3CH2CH2OH -- CH3CH2OCH3
C2H6 -- C3H8
dipole - dipole
H-bondingdipole-dipole
London
CH3Br
CH3CH2CH2OH
C3H8
Type molecular bondingType molecular bonding higher b.p.higher b.p.
NH3 -- PH3
NaBr -- PBr3
H2O -- HBr
PH3, dipole-dipole forces weaker, as stronger H-bonding w/ NH3
PBr3, dipole-dipole forces, as NaBr stronger ionic bonding
HBr dipole-dipole forces weaker than H-bonding in water
Which has a lower boiling pt in each pairWhich has a lower boiling pt in each pair
PROPERTIES OF LIQUIDS
Surface Tension@ surface molecules attracted only downward (no molecules above), so need KKE to break thru surface stronger forces > surface tension
Capillarityliq rises in small space against pull of gravity; forces acting bet cohesive (w/i liq) & adhesive forces
Viscosityresistancce to flow, inter- attraction slow liq movement incr T -- decr viscosity stronger inter- > higher viscdepends on: T & shape of molecule larger molecules higher visc long shape higher visc than small round shape (thnk of contact)
GAS - no attraction (far apart); random; highly compress; flow/diffuse ezly
LIQUID - some attraction (contact); random; not compress; flow/diffuse slower
SOLID - strongest attraction (fixed position); not compress; flow/diffuse not
Phase Changes
gas -------> liq condensation (exo)(endo) vaporization <-------
Shows changes that occur when add/remove heat @ const T
fig 11.22, pg 440
TE
MP
Heat Flow Out removed ---------->
GAS
GAS-LIQ
LIQUID
LIQ-SOLID
SOLID
Hovap
Hofus
GAS: q = m*Cgas*T GAS-LIQ: const T & EKE
ave speed is same at given T decr ave EPE but not EKE
H2O (g) & H2O (l) same EKE
liq EPE < gas EPE
@ same T; heat released = moles * (-vap)
q = n*(-Hovap)
results in largest amt of heat released WHY??? decr PE due from condensing dist. bet molecules
LIQUIDLIQUID q = m*Cliq*T * loss of heat results in decr T decr molecular speed, this decr EKE LIQ-SOLID * inter- attraction > motion of molecules * loss EPE form crystalline solid * const T & EKE
2 pts @ const Pw/i phase: q is T (EKE)depends on: amt subst (n), C for phase, T during phase : q (@T)(EPE), dist bet molecules changes
LIQ-GAS EQUILIBRA
@ const T
open closed
vaporize condense
Weaker bonds = higher vp,lower bp Keep in Mind: when a sys at equil is distr,will react in way to counteract said disturbto regain a state at a new equilib
gas liq
onvaporizati
oncondensati
Sys reaches pt of dynamic balance@ equilibria & vp const
Solids decr vp < liq
Solids: high vp
SOLID - GAS EQUILIBRA: Sublimation
gas solid sublime
Phase Diagrams???
SUMMARY CH. 11
Clausius-Claperyron
EQUILIBRA
gas -------> liq condensation (exo)(endo) vaporization <-------