1. 1 Chapter 12: Liquids, Solids and Interparticle Forces

2. 2 What is a liquid? A solid? Properties of liquids and solids: depend on Interparticle (Intermolecular) forces - vaporization/condensation/freezing - equilibrium vapor pressure/volatility - surface tension - boiling point/freezing point We are going to learn about Interparticle or Intermolecular forces first!

3. 3 TYPES OF INTERPARTICLE FORCES - SEE HANDOUT All forces of attraction between atoms, ions, molecules are “Interparticle” forces Includes ionic bonding, covalent bonding, metallic bonding, and ion-dipole attraction Important Subcategory is Intermolecular Forces Also called Van Der Waal’s forces Weak to moderate forces of attraction Not a type of bonding Includes three main ones: London Dispersion Forces, Dipole-dipole Attraction and Hydrogen Bonding Attraction

4. 4 Intermolecular Forces 1. London dispersion forces (LDF) - Small to moderate strength - Depend on size of electron cloud (and so also molar mass) of atom or molecule - Noble gases, diatomic elements, and many other nonpolar compounds

5. 5 Nonpolar molecules such as H 2 can develop instantaneous dipoles and induced dipoles. The attractions between such dipoles, even through they are transitory, create London dispersion forces. (See figures 12.17 & 18)

6. 6 Table 12.4: Dispersion Force and Molar Mass

7. 7

8. 8 Intermolecular Forces 2. Dipole-dipole attraction - Moderate strength - Molecules that have polar covalent bonds - Polar molecules  + and  - attraction Table of Properties of Hydrohalogens H-FH-ClH-BrH-I  EN1.41.10.80.4 # e-s10183654 BP291188206238

9. 9 There are many dipole-dipole interactions possible between randomly arranged ClF molecules. In each interaction, the positive end of one molecule is attracted to the negative end of a neighboring ClF molecule.

10. 10 Polarity and Dipole-to-Dipole Attraction

11. 11 Intermolecular Forces 3. Hydrogen-bonding (enhanced dipole- dipole) - Strong force, but much less than real bonding - Memory helper: E.T. FON Home: only F-H, O- H and N-H have this type of force - Due to small radius and high EN - See in boiling point data

12. 12 Depiction of hydrogen bonding among water molecules. The dotted lines are the hydrogen bonds.

13. 13 Figures 12.22 & 24: Intermolecular H-Bonding

14. 14 Hydrogen Bonding and Water: Water - 80% hydrogen-bonded - very tight arrangement (also high viscosity high density and high specific heat) Ice - crystal is very open, less dense than liquid (4. Dipole - induced dipole between diff types of molecules, O 2 in H 2 O)

15. 15 Diagrams of hydrogen bonding involving selected simple molecules. The solid lines represent covalent bonds; the dotted lines represent hydrogen bonds.

16. 16 If there were no hydrogen bonding between water molecules, the boiling point of water would be approximately - 80C.

17. 17 Notice that molecules with F-H, O-H and N-H have HIGH BPs because of Hydrogen-bonding forces of attraction.

18. 18 Properties and H-Bonding NameForm-ula Molar Mass StructureBP,°CMP,°C Sol’b in Water Ethane C2H6C2H6C2H6C2H630.0-88-172immisc Methanol CH 3 OH 32.064.7-97.8misc-ble Table on page 411 in Tro.

19. 19 Chemistry at a Glance: Intermolecular Forces

20. 20 PRACTICE IDENTIFYING THE TYPE OF IM FORCE: CH 4(g) C 6 H 6(l) Br 2(l) HBr (l) IBr (s) CH 3 OH (l)

21. 21 There are six changes of state possible for substances: learn all 6

22. 22 Distinguishing Properties of Solids, Liquids, and Gases

23. 23 BP, FP, Phase Changes, and  H o phase Boiling point: temperature at which the vapor pressure of a liquid is equal to the external pressure above the liquid, usually atmospheric pressure of 1 atm Freezing point: temperature at which a liquid changes into a solid at 1 atm

24. 24 BP, FP, Phase Changes, and DH o phase Phase changes: changes of state Learn all six Accompanied by heat flow called Enthalpy of phase change or  H o phase Heat of vaporization: liquid to vapor; energy (J) to vaporize 1 mol at constant T & P Heat of fusion: solid to liquid; energy (J) to melt 1 mol at constant T & P

25. 25 BP, FP, Phase Changes, and  H o phase Sensible heat transfer: temperature is changed but not phase q = m * c p *  T m is mass, c p is specific heat and  T is T f – T i See example (13.1***) Latent heat transfer using  H o phase : phase changes but not temperature q = m *  H o phase m is mass or moles depending on units See example (13.2***)

26. 26 BP, FP, Phase Changes, and  H o phase Specific heat: energy required to raise temperature of 1.00 gram of substance by 1.00 o C c p for water is 4.184 J/g.o C

27. 27 In the evaporation of a liquid in a closed container (a), the liquid level drops for a time (b) and then becomes constant (ceases to drop). At that point a state of equilibrium has been reached in which the rate of evaporation equals the rate of condensation (c).

28. 28 Equilibrium Vapor Pressure In closed system: at any given temperature, rate of vaporization = rate of condensation At dynamic equilibrium: means number of molecules in gas phase and number of molecules in liquid phase stay the same, but processes still happening Vapor pressure taken at equilibrium = the partial pressure Vapor pressure changes with change in temperature (listen to weather) Plot as vapor pressure curves: pressure vs. temperature (see Fig 13.6) Boiling point anywhere along curve: see bubbles rise to surface Normal boiling point is when vapor pressure is 1.00 atm or 760. Torr

29. 29 Vapor Pressure of Water at Various Temperatures.

30. 30 Boiling Point of Water at Various Locations That Differ in Elevation

31. 31 Just read about surface tension and capillary action Just read section (****13.10 and skip section 13.11