Name the strongest force first and the phenomena line up behind it. The tool below drills that habit from your notes.
WeSolve+ reads the whole document and writes the questions for you
Upload your PDF, photograph your notebook, or point the camera. WeSolve+ writes questions from that material, explains why each answer is right, reads the chapter back to you as a podcast, and remembers every item you missed until you own it.
The tool below is a small browser-only tool and it is not WeSolve+: paste a few lines and text rules turn them into cards on the spot. The real app, the one that uses AI, is behind the link above.
Unit 3 forces and laws, from your own notes
This is a browser-only tool, and that is all it isIt splits the text you paste by rule, and nothing else. WeSolve+ is a different thing entirely: it reads your whole PDF with AI, writes the reasoning behind every question, speaks the chapter back to you, and remembers what you missed so it can return it. Try the real app now, free!
Cards come out of the rules applied to your paste. The tool never saw the lecture, so it can only be as complete as the text you gave it.
Rank the forces before touching the phenomenon
Every substance has London dispersion, polar molecules add dipole attractions, and hydrogen bonding needs H bound to N, O or F. Boiling point comparisons are decided by that ranking plus particle size, since dispersion grows with electron count. Answers that argue from the force ranking read as chemistry; answers that argue from memory of one example read as luck.
Solubility is force matching, and the phrase is a mechanism
Like dissolves like works because dissolving trades solute and solvent attractions for solute to solvent ones, and the trade only pays when the new attractions are comparable. Polar and ionic species ride water's dipoles; oils settle for dispersion partners. Saying the trade, old attractions for new, is what turns the slogan into credit.
Ideal gases are a stated assumption, and the exam tests its edges
The ideal gas law assumes particles with no volume and no attractions, which holds when gases are hot and dilute. Cold and crowded, real gases deviate: attractions drag measured pressure down, particle volume props it up. Questions ask which assumption failed and in which direction, and the two named causes are the whole answer.
Mixtures keep their parts, and partial pressure is the proof
In a gas mixture each component presses on the walls in proportion to its mole fraction, unchanged by its neighbours. Collecting a gas over water then means subtracting water vapour's share before any calculation. The subtraction step is small, printed in the data, and the most reliably forgotten line in the unit's lab problems.
Separation and spectroscopy turn structure into data
Chromatography separates components by how strongly they cling to the stationary phase against the mobile one, which is the force ranking again wearing lab equipment. Beer's law turns colour into concentration through absorbance. Both appear in experimental prompts where the credited answer names the interaction doing the work, and the machine is only the messenger.
What to photograph for Properties of Substances and Mixtures
Your force rankings and gas law work. Related: Unit 2, photo to quiz and pricing.
Sources used on this page
- College Board, AP Chemistry
- Intermolecular force
- London dispersion force
- Ideal gas law
- Chromatography
- Active recall
- Spaced repetition
- Testing effect
- Forgetting curve
- Generation effect
- Judgment of learning
- Metacognition
- Desirable difficulty
- Distributed practice
- Formative assessment
- Flashcard
- Cloze test
- Multiple choice
- Test (assessment)
- Educational assessment
- Advanced Placement
- Curriculum
- Study skills
- Study guide
- Note-taking
- Overlearning
- Instructional scaffolding
- Item analysis
- Mastery learning
| Observation | Force at work | The credited sentence |
|---|---|---|
| Water boils far above methane | Hydrogen bonding | Stronger attractions cost more to break |
| Larger alkanes boil higher | Dispersion grows with size | More electrons, more contact |
| Salt dissolves in water | Ion dipole attraction | New attractions repay the old |
| Oil refuses water | Mismatched polarity | The trade does not pay |
| Real gas below ideal pressure | Attractions between particles | Cold and crowded, assumption fails |
| Pigments split on paper | Stationary phase affinity | Clingier components travel less |
What does AP Chemistry Unit 3 cover?
Intermolecular forces, solids, liquids and gases, solutions, ideal and real gas behaviour, chromatography and spectroscopy.
How do I compare boiling points?
Rank the strongest intermolecular force in each substance, then use particle size for ties, since dispersion grows with electron count.
When does hydrogen bonding apply?
When hydrogen is bound directly to nitrogen, oxygen or fluorine. Proximity to those atoms elsewhere in the molecule is the planted distractor.
When do real gases deviate from the ideal law?
At low temperature and high pressure: attractions lower the measured pressure and particle volume raises it, each failing one stated assumption.
What does Dalton's law say about mixtures?
Each gas contributes pressure in proportion to its moles, so collecting over water means subtracting water vapour's partial pressure first.
Can I build questions from my own Unit 3 notes?
Yes. The questions follow the upload: photograph these pages or attach the PDF, and nothing outside them enters the set.
Last updated: 2026-08-15