Cram AP Chem Unit 3: Intermolecular Forces and Properties

Overview of topics covered:
- Intermolecular forces (hydrogen bonding, dipole-dipole, London dispersion)
- Ideal gas law and deviations
- Spectroscopy and Beer's Law

Definition:
- Forces of attraction between molecules, crucial for understanding physical properties.
Types of intermolecular forces:
1. London Dispersion Forces:
  - Occurs between non-polar molecules and noble gases.
  - Weak attractive forces due to temporary dipoles.
2. Dipole-Dipole Interactions:
  - Occurs between polar molecules.
  - Stronger than London dispersion; involve permanent dipoles.
3. Hydrogen Bonding:
  - Special type of dipole-dipole interaction with hydrogen bonded to N, O, or F.
  - Strongest intermolecular force.
4. Ion-Dipole Forces:
  - Occur between ions and polar molecules (strongest overall).

Characteristics:
- Formed due to temporary dipoles in non-polar molecules.
- Dependent on polarizability (size and electron count) and contact area.
Example comparisons:
- CCl4 vs. CH4: CCl4 is larger and has stronger London dispersion forces.
- C2H6 vs. C4H10: Butane has more electrons and a larger contact area, resulting in stronger London dispersion forces.

Characteristics:
- Occur between molecules that are polar.
- Example: HCl aligns with oppositely charged regions attracting one another.
Important note: All polar molecules exhibit both dipole-dipole and London dispersion forces.

Description:
- Strongest intermolecular force; occurs in highly polar molecules with H-N, H-O, or H-F bonds.
Example: Water's H bonds create unique properties like high boiling point and surface tension.

Definition:
- Attractive forces between ions and polar molecules, crucial for solubility.
Example: NaCl in water forms ion-dipole interactions with cations and anions surrounded by water molecules.

Formula:
- PV = nRT,
  - P = pressure, V = volume, n = moles, R = gas constant, T = temperature.
Characteristics of gases:
- Gas pressure is related to collision frequency; more particles = higher pressure.
Example application: Reducing volume in a sealed container raises pressure.

Definition:
- Study of how light interacts with matter, used to analyze concentrations of solutions.
Spectrophotometry process:
- Light source -> monochromator -> sample solution -> detector.
Beer's Law:
- A = abc,
  - A = absorbance, a = absorptivity, b = path length, c = concentration.
Relationship:
- Higher concentration = higher absorbance; linear relationship.

Distillation: Used for separating liquids with different boiling points (e.g., alcohol and water).
Chromatography:
- Paper chromatography separates components based on polarity and size.
- Column chromatography allows substances to move through a stationary phase and separate.
Electromagnetic Spectrum:
- Range includes gamma rays, x-rays, visible light, infrared, microwaves, radio waves.
- Key relationships: Higher frequency (Nu) = shorter wavelength (Lambda).
Photoelectric Effect:
- Phenomenon demonstrating the particle nature of light; photon energy = E = hNu.
- Illustrates electron ejection based on photon energy (dependent on frequency).

Composed of molecules held together by intermolecular forces (such as Van der Waals forces, hydrogen bonds).
Generally have lower melting and boiling points.
Poor conductors of electricity and heat.
Example: Ice (solid water).

Made up of metal atoms bonded by metallic bonds, characterized by a sea of delocalized electrons.
Exhibit high electrical and thermal conductivity.
Malleable and ductile, with varying melting points.
Example: Copper (Cu).