1. Chapter 11: Liquids and Solids
Intermolecular Forces
The addition of heat changes the state of a compound from solid to liquid to gas as kinetic and potential energy are added to the molecules
Kinetic Energy involves the motion of the molecules
Potential Energy involves how far apart the molecules are
Intermolecular Forces hold the molecules together
Ion-Dipole Interactions: Na+Cl- interactions with water
Dipole-Dipole Attractions: interaction of polar molecules
Hydrogen Bonding: special dipole-dipole attraction in molecules where H is bonded to an electronegative atom (O, N, F, etc…)
Small size of H lets the dipoles get very close
Large electronegativity difference makes attraction great

2. Intermolecular Forces Ion-Dipole Forces
Dipole-Dipole Forces H-Bonding

3. d. London Dispersion Forces: temporary dipole moments can form when electrons are unsymmetrically distributed. Even nonpolar molecules have this type of attraction.

4. 3. Boiling point trends and Intermolecular Forces
Boiling Point increases as Mass and Intermolecular Forces Increase
i. Dipole moment decides B.P. if similar mass compounds
ii. Longer alkanes have more surface area = more dispersion forces
iii. H2O doesn’t follow the trend: H-bonding holds water together

6. The liquid state Liquids are required for life
Water solutions are required for many biological reactions to occur
Food preparation, cleaning, cooling, etc… require liquids
Characteristics of liquids: non-compressible, takes shape of container, dense
Surface Tension = resistance of a liquid to an increase in its surface area
Surface molecules are not involved in all possible intermolecular bonding
Requires energy to go the surface, so liquid resists increases in surface area
The higher the intermolecular forces, the higher the surface tension

7. Capillary Action = spontaneous rising of a liquid up a narrow tube
Adhesive Forces = polar liquid has intermolecular forces with polar surface
Cohesive Forces = intermolecular forces of the liquid for itself
Water: Adhesive (H-Bonding) > Cohesive, so concave meniscus
Mercury: Cohesive (London) > Adhesive, so convex meniscus
Viscosity = a liquid’s resistance to flow
Large intermolecular forces would cause high viscosity (glycerol)
Large, complex molecules can become physically entangled (grease)
Structural Model for Liquids
Gas: molecules so far apart, treat as if no intermolecular forces
Solid: molecules strongly held together, treat as if no motion
Liquid: strong forces plus motion of particles
Ordered regions (but less so than solids) that are changing all the time

8. The Solid State Classification of Solid Structures
Crystalline Solids = regular arrangement of components in 3 dimensions
Amorphous Solids = disordered arrangement of components
Will not be the focus of this chapter
Glasses = “frozen solutions” are disordered, amorphous solids
Crystal Structure Basics
Crystal = a piece of a crystalline solid
Lattice = 3-dimensional system of designating where components are
Unit cell = smallest repeating unit of the lattice
Examples: simple cubic, body-centered cubic, face-centered cubic

10. Three different cubic unit cells and lattices

11. X-Ray Analysis of Crystalline Solids
Diffraction = scattering of light by a crystal’s regular array of components
Wavelength of light must be about the same as the spacing of units
Constructive interference occurs when different distances traveled by the same wavelength of light is an integer multiple of l
Destructive interference occurs elsewhere

12. Diffractometer = computerized system to rotate crystal while shining X-rays at them and to record the diffraction data produced
Diffraction pattern tells us about how far apart the components are
Bragg Equation: nl = 2dsinq
Lets us calculate the distance between crystal components
Bragg’s awarded 1915 Nobel Prize for crystallography
Example: find d if n = 1, l = 1.54 Å, q = 19.3o

13. 4. Types of Crystalline Solids

14. Metal Structure and Bonding
The type of crystalline structure helps us explain the properties of solids
Argon (Group8A): mp = -189 oC, insulator for heat and electricity
Diamond (Network Atomic): mp = 3500 oC, very hard, insulator
Copper (Metallic Atomic): mp = 1083 oC, conductor, malleable, ductile
Metal Structure and Bonding
Properties (see Copper above) result from non-directional covalent bonds
Malleable and High mp: indicates strong, non-directional bonds
Difficult to separate
Easy to move positions, as long as they stay in contact
Electron Sea Model = valence electrons don’t belong to any specific atom
Array of metal cations surrounded by a sea of valence electrons
This would also account for electrical and heat conductance
Band (or MO) Model = Large MO’s form from billions of AO’s
When two atoms bind, we can form two widely spaced MO’s
When many atoms bind, we form a closely spaced band of MO’s
Core electrons still localized, only valence electrons in the “sea”
Empty MO’s available to electrons: heat/electricity conductance

15. Electron Sea
Model
Band or MO Model