1. Chapter 11: Intermolecular Forces

2. Intermolecular Forces Intermolecular forces are attractions (and repulsions) between molecules.

3. Intermolecular Forces The extent and nature of intermolecular forces cause the three phases of matter: Solid Close particle distances “Fixed” particle positions Most ordered arrangement of particles Liquid Increased disorder in particle arrangement Particles move throughout the bulk Particles are relatively close together Gas No order in particle arrangement Particles move throughout entire container Particles are far apart

4. Intermolecular Forces There are four major types of intermolecular forces:

5. Intermolecular Forces There are four major types of intermolecular forces: 1)Ion-Ion and Ion-dipole interactions: only present when ions are present 2)Dipole-dipole interactions: only present for polar molecules

6. Intermolecular Forces There are four major types of intermolecular forces: 1)Ion-Ion and Ion-dipole interactions: only present when ions are present 2)Dipole-dipole interactions: only present for polar molecules 3)‘London’ Dispersion forces (Van der Waals forces): present for all molecules, increasingly important for non-polar molecules

7. Dispersion Forces

8. Dispersion Forces and Polarization Dispersion forces will increase with: Increasing polarizability Increasing surface area (“size”)

9. Intermolecular Forces There are four major types of intermolecular forces: 1)Ion-Ion and Ion-dipole interactions: only present when ions are present 2)Dipole-dipole interactions: only present for polar molecules 3)(London) Dispersion forces/Van der Waals forces: present for all molecules, most important for non-polar molecules 4)Hydrogen-bonding: extremely important for compounds containing H-O, H-N, H-F bonds

10. Hydrogen Bonding

11. Hydrogen Bonding In Ice

12. Intermolecular Forces - A Recap As intermolecular forces increase, molecules will “stick” together more (it requires more energy for molecule separation)

13. Boiling Point

14. Melting & Boiling Points

15. Changes in States of Matter Any change of state will cause an enthalpy change :

16. Changes in States of Matter

17. Phase Diagrams

19. Phase Diagram for CO 2 and Water

21. Vapor Pressure At the surface of all liquids, molecules are undergoing liquid-gas phase transitions. The amount of vaporization above a liquid (measured as pressure) is the vapor pressure

22. Vapor Pressure Curves A substance boils when its vapor pressure equals atmospheric pressure (The “normal” boiling point is for an external pressure of 1 atm)

23. (e) (d) (c) (b) (a) Vapor Pressure Curves The Clausius-Clapeyron Equation