AP Chemistry Unit 3 Lecture Notes

Introduction

• Discussion on AP Chemistry, focusing on Unit 3.
• Key topics: Intermolecular forces, solids, liquids, gases, ideal gas law, solutions, solubility, light absorption.

Intermolecular Forces (IMF)

• Definition: Attractive forces between molecules.
• Types of IMFs:
  • Ion-Ion Forces: Strongest, between oppositely charged ions.
  • Ion-Dipole Forces: Between ions and polar molecules, e.g., salt in water.
  • Dipole-Dipole Forces: Between polar molecules, includes hydrogen bonding.
  • London Dispersion Forces: Weakest, occurs in nonpolar molecules due to induced dipoles.
• IMF Strength Order: Ion-Ion > Ion-Dipole > Hydrogen Bonding > Dipole-Dipole > London Dispersion.

Solids, Liquids, and Gases

• Types of Solids:
  • Ionic Solids: Form crystal lattices, high melting point, conduct electricity when dissolved.
  • Covalent Network Solids: Strong (e.g., diamond), no electrical conductivity.
  • Molecular Solids: Held by IMFs (e.g., ice), softer with lower melting points.
  • Metallic Solids: Conductors of heat and electricity due to delocalized electrons.
• Energy and Phase Changes: Energy is required to change phases, breaking or weakening IMFs.

Ideal Gas Law

• Equation: PV = nRT
  • P = pressure, V = volume, n = moles, R = gas constant, T = temperature.
• Units: Ensure units are consistent (e.g., atmospheres, liters, Kelvin).
• Dalton's Law: Total pressure of gas mixture is sum of partial pressures.

Kinetic Molecular Theory

• Gas particles move randomly, no energy loss in collisions, move in straight lines.
• Average kinetic energy proportional to temperature.
• Maxwell-Boltzmann Diagrams: Show distribution of molecular speeds in gases.

Deviation from Ideal Gas Law

• At High Pressure/Low Temperature: Gases deviate due to volume of particles and IMFs.
• Van der Waals Equation: Corrects for these deviations.

Solutions and Solubility

• Molarity (M): Moles of solute per liter of solution.
• Dilution: M1V1 = M2V2 for dilutions.
• Solubility Rules: Group 1A, nitrate, and ammonium compounds are soluble.

Electromagnetic Spectrum and Light

• Electromagnetic Spectrum: Range of all types of EM radiation.
• Photoelectric Effect: Electrons ejected from metal when hit by light of sufficient energy.
• Beer's Law: A = εbc, relates absorption to concentration.

Conclusion

• Overview of all discussed topics.
• Encouragement to ask questions or review material for better understanding.