1. Intermolecular Forces, Liquids, and Solids
Chapter 11/12

2. Warmup: Phase Changes
What is the vocabulary used with phase changes?
What happens in a phase change at the particle level?

3. Intermolecular Forces vs. Intramolecular Forces

5. Intermolecular Forces
The stronger the attractive forces in a liquid, the higher the boiling point
The stronger the attractive forces in a solid, the higher the melting point

6. Intermolecular Forces
Dipole-Dipole Force, London Dispersion forces, and hydrogen bonding forces
A fourth force is an Ion-Dipole Force
All four forces are electrostatic and tend to be less than 15% as strong as an ionic or covalent bond

7. Ion-Dipole Forces
exist between the ion and the partial charge on the end of a polar molecule
important in solutions

8. Dipole-Dipole Forces
Neutral polar molecules attract to each other when the positive end of one molecule is near the negative end of another
Strength depends on polarity
Weaker than ion-dipole forces

9. London Dispersion Forces
the motion of electrons in an atom or molecule can create an instantaneous dipole moment

10. London Dispersion Forces
Strength of force is based on polarizability
Polarizability increases with increasing molecular weight and complexity of shape
LDF’s exist between all molecules, polar and nonpolar

11. Which of these substances has greater London dispersion attractions?
Sample Exercise 11.1 Comparing Intermolecular Forces
The dipole moments of acetonitrile, CH3CN, and methyl iodide, CH3I, are 3.9 D and 1.62 D, respectively.
Which of these substances has greater dipole–dipole attractions among its molecules?
Which of these substances has greater London dispersion attractions?
The boiling points of CH3CN and CH3I are K and K, respectively. Which substance has the greater overall attractive forces?

12. Of Br2, Ne, HCl, HBr, and N2, which is likely to have
Sample Exercise 11.1 Comparing Intermolecular Forces
Of Br2, Ne, HCl, HBr, and N2, which is likely to have
(a) the largest london dispersion forces,
(b) the largest dipole–dipole forces?

13. Hydrogen Bonding Considered a unique dipole-dipole interaction
Force between the H atom in a polar bond (H-F, H-O, or H-N) and an unshared electron pair on a nearby electronegative ion or atom(usually N,F, or O)
Stronger than dipole-dipole or dispersion forces

14. Hydrogen Bonding

15. Sample Exercise 11.2 Identifying Substances that Can Form Hydrogen Bonds
In which of the following substances is hydrogen bonding likely to play an important role in determining physical properties: CH4, H2NNH2, CH3F, H2S,CH2Cl2, H2O2, CH3COCH3, PH3 ?

16. Identify the attractive forces between the following:

17. Comparing Intermolecular Forces

18. Sample Exercise 11.3 Predicting the Types and Relative Strengths of Intermolecular Attractions
List the substances H2, CO, HF, and Ne in order of increasing boiling points.
Identify IMF’s present in the following substances and order their bp: CH3CH3, CH3OH, and CH3CH2OH.

19. Properties of Liquids Viscosity is the resistance of a liquid to flow
Stronger IMF, higher viscosity

20. Properties of Liquids
Surface tension is the energy required to increase the surface area of a liquid by a unit amount.
A force is pulling molecules from the surface inward.
Stronger IMF’s, stronger surface tension.

21. Phase Changes

22. accompanied by a change in energy of the system
Phase Changes
accompanied by a change in energy of the system

23. Heating Curves
Graph of the temperature of the system versus the amount of heat added.

25. Vapor pressure
Pressure exerted by a vapor in equilibrium with the liquid phase
A liquid boils when its vapor pressure equals the external pressure acting on the surface of the liquid

26. Phase Diagrams
graphical way to summarize the conditions under which equilibrium exists between different states of matter

27. General Phase Diagram
Includes three important curves which represent temperatures and pressures where the various phases can co-exist

28. General Phase Diagram
The line from A to B is the vapor pressure curve.
It represents the equilibrium between the liquid and gas phase.
The normal bp is found at 1 atm on this curve

29. General Phase Diagram Point B is where the critical P and T are found
Beyond the critical point the liquid and gas phase are indistinguishable

30. General Phase Diagram
The line AD represents the equilibrium between the solid and liquid
The mp and fp are identical, and differ only in direction
The normal mp is at 1 atm

31. General Phase Diagram
Line AC represents the equilibrium between solid and gas
Point A is the Triple Point, where the three phases intersect and are at equilibrium

32. Phase Diagram – special cases
The mp of water decreases with increasing pressure because the liquid form is more compact than the solid form.
There is no normal mp in CO2. At 1 atm pressure, the substance will sublime

33. Sample Exercise 11.6 Interpreting a Phase diagram
Describe any changes in the phases present when H2O is
kept at 0 °C while the pressure is increased from that at point 1
to that at point 5
(b) kept at 1.00 atm while the temperature is increased from
that at point 6 to that at point 9

34. Structures of Solids Crystalline Solids
Atoms, ions, or molecules are ordered in a well-defined three-dimensional arrangements; they have flat surfaces or faces and regular shapes
Quartz and diamond are crystalline solids

35. Structures of Solids Amorphous Solids
Solids in which particles have no orderly structure; lack faces and shape
Rubber and glass are amorphous solids

36. Structures of Solids

37. Bonding in Solids - Molecular Solids
Atoms or molecules (nonmetals) held together by IMF’s
Soft, low mp, poor conductors

38. Bonding in Solids – Covalent-Network Solids
Atoms held together in large networks or chains by covalent bonds
Hard, high mp, variable conductors

39. Bonding in Solids - Ionic Solids
Ions held together by ionic bonds (electrostatic forces)
Hard, brittle, high mp, poor conductors

40. Bonding in Solids - Metallic Solids
Metal atoms
Visualize the metals as an array of positive ions immersed in a sea of delocalized valence electrons
soft to very hard, low to high mp, excellent conductors, malleable and ductile

41. Alloys
Mixture of elements exhibiting metallic properties

42. Summary of Bonding in Solids