1. Liquids & Solids

2. Vocab you need to know: Intramolecular forces Intermolecular forces
dipole-dipole forces
ion-dipole forces
london dispersion forces
hydrogen bonding
Viscosity
Surface tension
Cohesive forces
Adhesive forces
Heating curve
Heat of fusion
Heat of vaporization
Critical temperature
Critical pressure
Vapor pressure
Boiling point
solids (molecular, covalent-network, ionic, and metallic)

3. Intramolecular Bonding
“Within” the molecule.
Molecules are formed by sharing electrons between the atoms.
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4. Solids & Liquids Caused by intermolecular forces (IMF)
Higher IMFs lead to higher melting points of solids and higher boiling points of liquids
IMFs in order of decreasing strength:
Hydrogen bonding (strongest) (broken bone)
Ion-dipole forces (tore ACL)
dipole-dipole forces (sprained ankle)
London dispersion forces (weakest) (paper cut)

5. Hydrogen Bonding really strong type of dipole-dipole force
exists only when hydrogen is bonded to F, O, or N (H-NOF)
accounts for water’s really high boiling point (compared to other molecular compounds) and the fact that water expands when it freezes and its high surface tension

6. Hydrogen Bonding
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7. Dipole Forces Ion-dipole forces exist btwn ions and polar molecule
enables some salts (ions) to dissolve in water (polar)
Dipole-dipole forces exist btwn separate polar molecules
dipole of one molecule attracts the dipole of another molecule

8. Dipole-Dipole Forces
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9. London Dispersion Forces
caused by induced (temporary) dipoles
exist for ALL atoms and molecules, but is only observable in non-polar molecules
atoms with higher amounts of electrons are more easily polarized and thus have stronger LD forces

10. London Dispersion Forces
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11. What type(s) of intermolecular forces exist between each of the following molecules?
HBr
HBr is a polar molecule: dipole-dipole forces. There are also dispersion forces between HBr molecules.
CH4
CH4 is nonpolar: dispersion forces. S O
SO2
SO2 is a polar molecule: dipole-dipole forces. There are also dispersion forces between SO2 molecules.
11.2

12. Concept Check
Which molecule is capable of forming stronger intermolecular forces?
N2 H2O
Explain.
H2O has the stronger intermolecular forces because it exhibits hydrogen bonding, whereas N2 only exhibits London dispersion forces.
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13. Liquid Properties
Viscosity – resistance to flow, increases with molar mass
Surface tension – caused by imbalance of IMFs at the surface of a liquid
Cohesive forces – bond to itself (like water molecules to themselves)
Adhesive forces – bond to something else (like water to glass tubing), causes a meniscus

14. attracted to each other
Properties of Liquids
Cohesion is the intermolecular attraction between like molecules
Adhesion is an attraction between unlike molecules
Adhesion
attracted to glass
Cohesion
attracted to each other
11.3

15. Melting and Boiling Points
In general, the stronger the intermolecular forces, the higher the melting and boiling points.
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16. The Boiling Points of the Covalent Hydrides of the Elements in Groups 4A, 5A, 6A, and 7A
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17. Phase Changes heating curves (we did one in earlier this semester)
heats of fusion (solid liquid) and vaporization (liquid gas) are the flat parts of a heating curve
nonpolar substances tend of have low critical temps and polar substances tend to have high critical temps (because of difference in IMFs)

18. Vapor Pressure
measure of how many molecules are in the gas phase vs. liquid/solid phase in a closed system
higher vapor pressures correspond to lower molar masses and weak IMFs
Increasing temp increases vapor pressure
the temperature when atmospheric pressure equals vapor pressure is the boiling point of a liquid (normal bp is temp at which vapor pressure equals 1 atm)

19. Changes of State 19 Copyright © Cengage Learning. All rights reserved

20. Heating Curve for Water
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21. A convenient way of representing the phases of a substance as a function of temperature and pressure:
Triple point
Critical point
critical temperature (Tc) - temperature above which the gas cannot be made to liquefy, no matter how great the applied pressure.
critical pressure (Pc) - minimum pressure that must be applied to bring about liquefaction at the critical temperature.
Phase equilibrium lines
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22. Phase Diagram

23. Concept Check
As intermolecular forces increase, what happens to each of the following? Why?
Boiling point
Viscosity
Surface tension
Enthalpy of fusion (solid to liquid)
Freezing point
Vapor pressure
Heat of vaporization (liquid to gas)
Boiling point increases
Viscosity increases
Surface tension increases
Enthalpy of fusion increases
Freezing point increases
Vapor pressure decreases
Heat of vaporization increases
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24. Types of Crystalline Solids
Ionic Solids – ions at the points of the lattice that describes the structure of the solid. Ion-ion is strong than all IM forces
Atomic Solids – atoms at the lattice points that describe the structure of the solid. Stronger than IM forces but generally weaker than ion-ion
Molecular Solids – discrete covalently bonded molecules at each of its lattice points. Held together with only IM forces
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25. Classification of Solids
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26. Network Solids
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27. Cross Section of a Metallic Crystal
Types of Crystals
Metallic Crystals – Typically weaker than covalent, but can be in the low end of covalent
Lattice points occupied by metal atoms
Held together by metallic bonds
Soft to hard, low to high melting point
Good conductors of heat and electricity
Cross Section of a Metallic Crystal
nucleus &
inner shell e-
mobile “sea”
of e-
11.6