Intermolecular Forces and Liquids and Solids
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Transcript of Intermolecular Forces and Liquids and Solids
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Intermolecular Forces and
Liquids and Solids
Chapter 11
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A phase is a ___________ part of the system in contact with other parts of the system but separated from them by a well-defined boundary.
2 Phases
__________ phase - ice
__________ - water
11.1
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Intermolecular Forces
11.2
I_____________ forces are attractive forces ________molecules.
I_____________ hold atoms ____________ in a molecule.
Intermolecular vs Intramolecular
• 41 kJ to vaporize 1 mole of water (inter)
• 930 kJ to break all O-H bonds in 1 mole of water (intra)
Generally, ____molecular forces are much weaker than ____molecular forces.
“Measure” of intermolecular force
boiling point
melting point
Hvap
Hfus
Hsub
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Types of Intermolecular Forces1. __________ (strongest)
11.2
The _________ is a special dipole-dipole interaction between the hydrogen atom in a polar N-H, O-H, or F-H bond and an electronegative O, N, or F atom. IT IS NOT A BOND.
A H…B A H…Aor
A & B are N, O, or F
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Hydrogen Bond
11.2
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Types of Intermolecular Forces
2. Ion-Dipole Forces
Attractive forces between an ion and a polar molecule
11.2
Ion-Dipole Interaction
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11.2
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Types of Intermolecular Forces
3. Dipole-Dipole Forces
Attractive forces between polar molecules
Orientation of Polar Molecules in a Solid
11.2
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Types of Intermolecular Forces4. Dispersion Forces – van der Walls forces/London forces (weakest)
Attractive forces that arise as a result of temporary dipoles induced in atoms or molecules
11.2
ion-induced dipole interaction
dipole-induced dipole interaction
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Intermolecular Forces4. Dispersion Forces Continued
11.2
Polarizability is the ease with which the electron distribution in the atom or molecule can be distorted.
Polarizability increases with:
• greater number of electrons
• more diffuse electron cloud
Dispersion forces usually increase with molar mass.
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SO
O
What type(s) of intermolecular forces exist between each of the following molecules?
HBrHBr is a polar molecule: dipole-dipole forces. There are also dispersion forces between HBr molecules.
CH4
CH4 is nonpolar: dispersion forces.
SO2
SO2 is a polar molecule: dipole-dipole forces. There are also dispersion forces between SO2 molecules.
11.2
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Properties of Liquids
Surface tension is the amount of energy required to stretch or increase the surface of a liquid by a unit area.
Strong intermolecular
forces
High surface tension
11.3
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Properties of Liquids
Cohesion is the intermolecular attraction between like molecules
11.3
Adhesion is an attraction between unlike molecules
Adhesion
Cohesion
attracted to glass
attracted to each other
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Properties of Liquids
Viscosity is a measure of a fluid’s resistance to flow.
11.3
Strong intermolecular
forces
High viscosity
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Eva
pora
tion
GreatestOrder
LeastOrder
11.8C
onde
nsat
ion
T2 > T1
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The ________________ is the vapor pressure measured when a dynamic equilibrium exists between condensation and evaporation
H2O (l) H2O (g)
Rate ofcondensation
Rate ofevaporation=
Dynamic Equilibrium
11.8
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Molar heat of vaporization (Hvap) is the energy required to vaporize 1 mole of a liquid.
ln P = -Hvap
RT+ C
Clausius-Clapeyron EquationP = (equilibrium) vapor pressure
T = temperature (K)
R = gas constant (8.314 J/K•mol)
11.8
C = constant (depends on P & T)
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The boiling point is the temperature at which the (equilibrium) vapor pressure of a liquid is equal to the external pressure.
The normal boiling point is the temperature at which a liquid boils when the external pressure is 1 atm.
11.8
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The __________________ (Tc) is the temperature above which the gas cannot be made to liquefy, no matter how great the applied pressure.
The ____________ (Pc) is the minimum pressure that must be applied to bring about liquefaction at the critical temperature.
11.8
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Mel
ting
11.8F
reez
ing
H2O (s) H2O (l)
The melting point of a solid or the freezing point of a liquid is the temperature at which the solid and liquid phases coexist in equilibrium
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Molar heat of fusion (Hfus) is the energy required to melt 1 mole of a solid substance.
11.8
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11.8
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Sub
limat
ion
11.8
Dep
ositi
on
H2O (s) H2O (g)
Molar heat of sublimation (Hsub) is the energy required to sublime 1 mole of a solid.
( Hess’s Law)
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A phase diagram summarizes the conditions at which a substance exists as a solid, liquid, or gas.
The triple point is where all 3 phases meet.
Phase Diagram of Water
11.9
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11.9
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Where’s Waldo?Can you find…
The Triple Point?
Critical pressure?
Critical temperature?
Where fusion occurs?
Where vaporization occurs?
Melting point (at 1 atm)?
Boiling point(at 6 atm)?
Carbon Dioxide
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11.9