2. The boiling point of a substance is a measure of the amount of energy needed to:  increase the speed of the molecules in the liquid phase to that of their gas phase (The heavier it is, the higher the boiling point)  overcome any intermolecular forces (“molecular stickiness”)

3. Consider the following polar molecules: Substance Boiling Point (  C) Molar Mass Dipole moment HF20 1.83 H2OH2O10018 1.80 HCl-8536 1.08 H2SH2S-6034 0.97 SO 2 -1064 1.61 The polarity of a molecule is more important in determining boiling point than its mass.

4. Water’s unusual properties are due to its: Surface tension: uneven distribution of the intermolecular dipole-dipole interactions increases the strength of the intermolecular hydrogen bonding at the surface Adhesive properties: the small size and high polarity of water causes it to adhere (wet) other polar substances Cohesive properties: a large molecular dipole moment causes water to stick to itself Non-polar polyester Polar spider silk (a polypeptide)

5. The three common states of matter are: Definite volume Definite shape Definite volume Indefinite shape Indefinite volume Indefinite shape

6. Three basic assumptions: 1.All matter is composed of small particles (atoms, molecules, ions). The amount of space (volume) that the particles take up depends upon the distance between the particles and not on the size of the particles themselves. 2.These particles are in constant random motion. 3.The particles undergo elastic collisions (no loss of energy) with each other and the walls of their container. Absolute zero: The temperature at which ALL molecular motion stops. (0 K = -273°C = -460°F)

7. Solids: The particles in solids can be arranged in three different ways. 1.In a regular repeating pattern that extends over long distances. A glassy material: Short-range order only A crystalline material: Has long-range order 2.With a pattern that only repeats over short distances.

8. 3. Amorphous solids have no long or short range order. Charcoal: Amorphous carbon Graphitic carbon: ‘glassy’ carbon Diamond: Crystalline carbon Allotropes: different structural forms of the same element

9. Polar bonds In covalent bonds, electrons aren’t shared equally between the two nuclei when there is a difference in electronegativity.* Electronegativity: Ability of an atom to attract electrons when in a molecule. Trend: Increases left  right, bottom  top HF ++ -- The permanent positive and negative charges on the molecule cause HF to be POLAR.

10. When electrons in a covalent bond are concentrated near one of the nuclei, the bond is POLAR. HF Polar covalent bond HH Nonpolar covalent bond If the electrons are shared equally between the nuclei, the bond is NONPOLAR. ++ --

11. Now, you try some... Do the following have polar or nonpolar bonds? F2F2 HCl BCl 3 S8S8 H2OH2O C 60 SO 2 BN nonpolar polar

12. Because of the ASYMMETRIC bent structure of water, water is a polar molecule. O H H Imagine that you’re holding up a mirror through one of the atoms in the molecule. If you can find a place where the molecule is different on either side of the mirror, the molecule is polar.  Both bonds in water are polar. How does this affect the polarity of the molecule? What about CO 2 ? This molecule is perfectly SYMMETRIC, which makes it NONPOLAR VE = 16, 4 bonds to C

13. Are these planar molecules polar or nonpolar? B F F F B F F H B H H H nonpolarpolarnonpolar Are these linear molecules polar or nonpolar? OC OCO SCO polarnonpolar polar

14. Three main types Intermolecular Forces: Whether a substance is a liquid, solid or gas depends upon the strength of the intermolecular forces between adjacent molecules. O O H H O O H H Let’s get to stickin’!! 1.H-bonding 2.Dipole-dipole 3.Induced dipole-induced dipole (also called London Dispersion Forces, or LDF) STRONGEST weakest

15. 1. H-bonding: Is a special case of dipole-dipole interaction because it is significantly stronger. It occurs whenever H is bonded to either N, O or F. ++ -- No intermolecular H-bonding possible H-bonding between H on OH and O on next OH 2. Dipole-dipole: interaction between polar molecules that do not have H-bonding (ex: H 2 S, PH 3, HCl)

16. 3. Induced dipole-induced dipole: A temporary redistribution of the electron cloud around a NONPOLAR molecule induces a temporary dipole in an adjacent NONPOLAR molecule. C 6 H 14 It is because of the increasing size of the electron cloud that: H H O O N N F F Cl are all gases at room temp. Br I I while is a liquid and is a solid.

17. Phase Diagrams SOLID LIQUID GAS Critical Point Triple Point vaporizationcondensation sublimation deposition melting freezing

18. Critical point: Temperature and pressure beyond which it is impossible to condense the vapor into a liquid Triple point: Temperature and pressure at which all three phases coexist Normal boiling point: Temperature at which a liquid will boil under 1 atm of external pressure Normal freezing point: Temperature at which a liquid will freeze under 1 atm of external pressure What are the normal boiling and freezing points of water in  C? Normal BP: 100  C Normal FP: 0  C

19. Temperature (  C) Pressure (atm) 5.11 1.00 -78 Phase Diagram for Carbon Dioxide Why is it not possible to have liquid CO 2 at atmospheric pressure? Because CO 2 won’t condense at pressures below 5.11 atm.

20. 1.00 atm 0C0C 100  C Q: In terms of IMF’s, why is water’s phase diagram so different from the phase diagram for CO 2 ? CO 2 H2OH2O A: There is intermolecular hydrogen bonding present in water, but only LDFs in CO 2. Therefore, it takes more energy to separate water molecules from each other.