The largest unit on the exam. London dispersion, dipole-dipole, and hydrogen bonding forces; solids, liquids, and gases; the ideal gas law and kinetic molecular theory; solutions and solubility; and spectroscopy.
Six ways to master Unit 3 — pick whichever fits how you like to study.
Twelve topics from the College Board CED, in order — the most of any unit.
Unit 3 is the largest unit on the AP Chemistry exam, and it's where the molecular shapes and polarities you predicted in Unit 2 finally pay off. Intermolecular forces — much weaker than the covalent and ionic bonds from Unit 2 — determine almost every macroscopic property you can observe: boiling point, viscosity, surface tension, and solubility. You'll also model gas behavior with the ideal gas law and kinetic molecular theory, learn why real gases deviate from ideal behavior, and study solutions, solubility, and spectroscopy.
This unit is roughly 18–22% of the AP Chem exam — nearly a quarter of all test questions — and spans 28–38 class periods, by far the longest unit. Expect IMF-based reasoning to show up constantly on both the multiple-choice and free-response sections.
The College Board ties Unit 3 to four Big Ideas — more than any other unit: