Reason from particle access to entropy change
Predict the sign of a system entropy change while distinguishing it from the total entropy criterion.
AP Chemistry preparation
Use spectra and composition evidence to choose a model, calculate a result and explain what remains unidentified.
This is the course outline. Open a unit to choose a lesson; every lesson opens on its own page. Explanations and experiments live inside those lesson pages.
Course scope and preparation
Mechanisms and evidence across Units 1–9
The 81 authored lessons span atomic structure, bonding, bulk matter, reactions, kinetics, thermochemistry, equilibrium, acids and bases, entropy, free energy and electrochemistry. Each module below links its actual investigations and explanations. Unit-specific public mixed reviews retain first responses and known exposure. The linked sixteen-investigation portfolio, AP-specific unknown-sample project and all-unit public rehearsal retain separate evidence. The source/outcome reconciliation distinguishes authored materials from actual supervised investigations and independently reviewed learner performance; no site interaction certifies those practical requirements.
Start with high-school chemistry or use the short recap in each lesson. Use algebra, ratios, logarithms, units and graph reading as needed; optional quantitative extensions are labeled. All lessons are directly accessible; existing HS chemistry achievements remain separate.
Try the six mixed Unit 1 evidence cases
Construct and revise your own Lewis diagrams
Thermodynamic direction and electrochemical evidence
Construct a standard reaction entropy ledger
Calculate reaction entropy using balanced coefficients, direction and extent.
Find when enthalpy and entropy favor change
Convert entropy units, calculate ΔG°, and justify temperature-dependent favorability.
Separate a favorable direction from an accessible rate
Explain kinetic persistence without changing equilibrium thermodynamics.
Use K and Q to decide the actual direction
Connect standard free energy to K and actual reaction free energy to Q/K.
Explain why dissolution is a balance of competing effects
Combine lattice, hydration and entropy terms without claiming a universal dissolution sign.
Require a mechanism before adding favorable reactions
Balance a coupled reaction and distinguish thermodynamic sufficiency from mechanistic connection.
Diagnose electrode roles and broken current paths
Identify oxidation, reduction, external electrons and ionic charge balance in both cell modes.
Keep voltage intensive while balancing electron transfer
Relate E°, ΔG° and K with correct electron balance and equation scaling.
Explain potential changes with the reaction quotient
Reason from composition to signed cell potential and distinguish direction from magnitude.
Infer deposited material from charge and stoichiometry
Convert current and time to electron amount, deposited mass and conditional efficiency.
Water ionization and acid-base evidence
Design a buffer that meets challenge and budget constraints
Construct and justify a buffer formulation against independent baseline, challenge and material-budget requirements, then transfer it to changed conditions.
Build a structural explanation of acidity
Justify a qualitative acid-strength comparison from controlled structural features while distinguishing proton donation, oxidation state and ideal aqueous pH.
Distinguish titration landmarks from indicator endpoints
Use stoichiometry and equilibrium to distinguish half-equivalence, equivalence and a stipulated observed endpoint, then justify an indicator-window decision.
Construct buffer reaction inventories before equilibrium
Construct nominal post-neutralization amounts and distinguish them from full equilibrium species when a buffer component is exhausted or the solution is diluted.
Construct conjugate-salt constants and species ledgers
Construct a reciprocal conjugate constant, validate hydrolysis direction through conserved charge and distinguish supported qualitative inference from unsupported pH.
Separate water and solute-depletion approximations
Select and justify a weak-equilibrium model from separate water and solute-depletion checks, then transfer the reasoning from an acid to a neutral base.
Build strong-acid/base inventories and test the water approximation
Construct a dissolved-ion inventory, verify formula and volume independently, and justify when a dominant-ion approximation is adequate.
Construct water-ion evidence without assuming neutral means pH 7
Use logarithms and a stated water-ionization reference to distinguish equal ion activities, equilibrium consistency and acidity relative to neutrality.
Dynamic balance and conserved composition
Construct a composition that satisfies both equilibrium and conservation
Use unequal stoichiometry, opposing rates and a reaction quotient to justify an equilibrium composition for a specified closed batch.
Transform the equation and its equilibrium constant together
Justify reciprocal, power and product transformations while refusing to assign a constant to a mismatched species equation.
Respect finite solid inventory when applying a solubility product
Distinguish saturated coexistence, exhausted undersaturation and impossible negative inventories while accounting for volume and a common ion.
Distinguish fixed-volume and fixed-pressure equilibrium disturbances
Use Q, K, conserved species units and the actual held constraint to justify gas-equilibrium responses.
Distinguish dissolved totals from the ions in a solubility product
Distinguish measured total concentration, free-ion concentration and activity when evaluating a solubility-product inference.
Compare thermal and mechanical changes in equilibrium
Explain why both Q and K may change during heating, then apply conservation and the actual held constraint to a new equilibrium.
Construct and challenge an equilibrium quotient
Represent a reaction quotient from its equation and phase labels, distinguishing expression validity from agreement at one state.
Infer a constant from an actual electrometric titration
Use a documented measurement chain to infer an equilibrium quantity while preserving activity conventions and evidence limits.
Build an equilibrium particle diagram with an honest scale
Connect particulate composition, molar inventory and concentration while distinguishing species count from conserved constituent units.
Heat measurement and reaction-energy evidence
Calibrate a calorimeter before inferring reaction enthalpy
Justify calorimeter calibration and signed heat transfer before normalizing by reaction extent.
Construct a Hess pathway without losing species or physical states
Construct a reaction-energy combination whose net species match a target, retaining reversal, scaling, reference states and uncertainty conventions.
Apply molar phase energy only within the available phase inventory
Relate heat to changed phase amount and distinguish nominal endpoints, source uncertainty and missing models beyond the phase interval.
Reaction-rate evidence and model discrimination
Design rate comparisons that distinguish competing orders
Infer bounded candidate orders from same-temperature initial rates, use units and a shared k, and explain which additional comparison discriminates remaining models.
Choose a defensible window for a reaction-rate estimate
Justify a rate-estimation window using reading bounds, depletion bias and baseline evidence, and withhold unsupported chemical rates.
Challenge competing concentration–time laws
Use concentration and transformed-time evidence to distinguish zero-, first- and second-order models without treating two-point agreement or a straight-looking plot as sufficient proof.
Build an elementary-step sum and test its rate prediction
Combine elementary steps into an overall ratio and use a stipulated slow first event to predict rates without copying overall coefficients into exponents.
Test when a pre-equilibrium substitution is defensible
Use a fast reversible-step approximation with explicit assumptions and diagnose when intermediate drain or short observation time invalidates it.
Distinguish energetic collisions from suitably oriented ones
Explain why collision energy, orientation and opportunity frequency are distinct, and use joint event evidence rather than assuming independent filters.
Construct transition states from local energy barriers
Construct a transition-state level from its adjacent minimum and barrier, reconcile forward/reverse differences and avoid inferring overall rates from peak height alone.
Construct a catalytic surface without double-counting its sites
Represent surface adsorption and release with conserved sites while separating eligible pairs, disjoint event capacity and unsupported rate claims.
Repair an enzyme inventory before claiming a steady rate
Conserve catalyst inventory and justify when a proposed enzyme composition supports a stationary product flux.
Infer radioactive half-life from corrected count evidence
Distinguish expected radioactive decay from detector readings and justify a bounded endpoint inference under explicit assumptions.
Construct an acid or base catalytic proton-transfer cycle
Use local atom and charge conservation plus net cancellation to justify a catalytic proton-transfer representation.
Reaction species and conserved change
Infer equivalence without mistaking an endpoint for proof
Infer analyte concentration from quantitative stoichiometry and explicitly qualified endpoint evidence, diagnose interval disagreement and transfer to a non-one-to-one reaction.
Construct conjugates without confusing H⁺ with H
Construct conjugate acid/base compositions and charges, explain a conserved-total counterexample and represent an amphiprotic species in both roles.
Construct electron-matched halves and recognize dual roles
Construct a closed redox equation from supplied halves, independently check atoms and charge, and distinguish oxidation-state assignments from physical charge.
Plan reaction extent when reagent supplies have bounds
Convert unlike reagent records into reaction capacities, inspect full ionic leftovers and qualify limiting-reagent claims under bounded inputs.
Build balanced coefficients—and test whether they are unique
Balance supplied reaction skeletons without changing formulas, reduce common factors and explain why conservation need not identify product proportions.
Construct a net ionic change without deleting matter
Build simplified ionic equations from supplied before/after species, distinguish weak-acid and physical-state conventions, and explain an unchanged excess portion.
Optical signals and inference limits
Test concentration inference with blanks and two wavelengths
Explain concentration/path/wavelength effects, distinguish exponential transmission from linear absorbance and diagnose single-analyte inference limits.
Match photon energy, transition direction and preparation
Convert photon wavelength/frequency/energy, balance absorption/emission signs and explain why a matching gap does not establish intensity.
Species inventories and solution representations
Repair a solution diagram using atoms, charge and concentration
Repair an ionic or molecular solution representation using independent element and charge budgets, then transfer to dilution and mixed salts.
Test mixture proposals with matched chromatograms
Calculate Rf with reading bounds, account for every spot and test co-migration with a second mobile-phase condition.
Compare solubility without confusing amount, rate and interactions
Normalize dissolved mass, distinguish saturation from short-time and all-dissolved records, and qualify a solvent explanation using competing interactions.
Molecular motion and full distributions
Compare molecular speed distributions and threshold fractions
Use normalized speed curves and threshold areas to distinguish mass, temperature and energy effects.
Distinguish weak corrections from cancelling gas effects
Explain pressure departures using separate particle assumptions and challenge ideality claims with changed conditions.
Vapor inventories and supported phase conditions
Test when adding substance changes vapor pressure
Distinguish saturation pressure from actual pressure and account for vapor and liquid amounts.
Find a boiling condition without extrapolating a fit
Convert pressure units, check a fitted interval and interpret a conditional boiling temperature.
Infer dry gas from water levels and a wet pressure
Combine hydrostatic equilibrium, saturation pressure and Dalton’s law to infer retained dry inventory and explain competing errors.
Build phase cartoons while conserving intact molecules
Construct compact ordered, compact disordered and dispersed representations of the same molecular inventory, and distinguish static geometry from motion and phase evidence.
Atomic and composition evidence
Infer isotope composition from a mass spectrum
Calculate isotope fractions and a weighted mass, test scaling invariance and explain what an empty or bounded signal establishes.
Decide what elemental composition can identify
Derive an empirical ratio, use an independent molar mass to test a molecular formula, and diagnose feasible, impossible and nonidentifiable binary mixtures.
Connect photoelectron peaks to electron structure
Reconcile a schematic spectrum with a ground-state configuration and test how photon energy changes the energy ledger while binding levels remain fixed.
Configurations, ionization and attraction
Diagnose an atom or ion electron configuration
Audit proposed nitrogen, oxygen and ion configurations; distinguish charge errors, forbidden pairing, higher-energy arrangements and incorrect ion-removal order.
Test periodic explanations with ionization evidence
Calculate a signed energy difference and ratio, distinguish first from successive removal and defend a structural explanation with source provenance.
Separate charge, distance and removal-energy claims
Calculate independent charge/distance effects, compare inverse-square force with inverse-distance separation work and qualify an isoelectronic explanation.
Periodicity, valence and evidence limits
Distinguish electron attachment from electron removal
Write attachment and detachment processes, calculate their energy changes and explain why fluorine/chlorine challenges a smooth trend.
Choose the property that answers the bonding question
Use relative electronegativity to predict bond-attraction direction, test coordinate reversal and equal-atom controls, and reject an affinity-based polarity inference.
Connect valence patterns to a complete energy argument
Balance electrons and common ionic charges, sum successive removal and attachment terms, and separate a conditional energy decrease from reaction-rate evidence.
Bond potentials and structural representations
Read bond length and separation energy from a curve
Locate the equilibrium separation and well depth, predict force direction on either side and reconcile finite and infinite external-work calculations.
Audit formal charge and compare resonance contributors
Reconcile ion electron budgets, local octets and formal charges; distinguish equivalent contributors from less-supported non-equivalent proposals and from measured partial charge.
Molecular shape and local orbital models
Separate electron geometry, molecular shape and polarity evidence
Translate AX/E region counts into electron and molecular geometry, inspect axial/equatorial distinctions and test equal versus unequal bond contributions without claiming measured dipoles.
Count sigma and pi bonds without miscounting electron regions
Reconcile whole-graph shared-pair counts with local neighbors/lone pairs, assign restricted sp/sp²/sp³ labels and explain the overlap distinction and model limits.
Rotate a dipole and test the competing charge interactions
Use explicit partial-charge positions to explain orientation dependence and distinguish finite-pair energy, radial force and an asymptotic approximation.
Reference measurements and matched comparisons
Compare bond distances without hiding unmatched evidence
Calculate signed and relative bond-distance differences while distinguishing atom identity, bond order, molecular environment and the source distance definition.
Test a bond-stiffness claim against isotope evidence
Predict a stiffness ratio, reconstruct a target vibrational coefficient and compare naive versus reduced-mass-corrected inferences without treating frequency as dissociation energy.
Distinguish successive bond breaking from a mean bond value
Calculate specific dissociation, atomization and mean enthalpies while preserving species, phases, reaction direction and shared uncertainty.
Ionic ordering and metallic alloy representations
Connect ionic ordering to many-particle interactions
Distinguish formula ratio from local coordination, explain attraction and repulsion despite net neutrality, and test charge/distance scaling without treating a finite patch as a measured crystal.
Distinguish alloy composition from a geometric fit
Represent substitutional versus interstitial changes, reconcile atom fractions and site occupancy, and evaluate a stated geometric clearance without inferring real alloy stability or properties.
Separate a molecular solid, a layer and a connected framework
Distinguish discrete molecules from layered and three-dimensional covalent connectivity, using explicit path and contact accounting without claiming a measured material strength.
Material properties and independent representations
Test alloy-property claims against matched reference data
Separate resistance from resistivity and judge which composition or temperature comparisons support a material claim.
Construct a material representation without overclaiming evidence
Construct and critique an atom-count representation using a mass-to-atom reference and distinguish composition, arrangement and mobile charge.
Projects, practice and evidence
Evidence boundaries
Isotope masses and selected NIST ionization rows are source-linked reference values; detector signals and composition/PES packets are original teaching constructions. None is a performed physical experiment. The different lesson packets are different samples; do not combine them as evidence for one unknown. Public practice and saved notebook presence do not establish independent mastery.
The official AP Chemistry audit requires supervised laboratory evidence, time and investigation breadth. This site does not establish authorization, credit, laboratory proficiency or fulfillment of those requirements. The opening path uses supplied records and requires no chemicals or equipment.
Connect bonding evidence in eight mixed Unit 2 cases
Connect gases, solutions and spectra in eight mixed Unit 3 cases
Connect reaction representations in eight mixed Unit 4 cases
Connect kinetics and evidence limits in eight mixed Unit 5 cases
Connect heat, phase and reaction-energy evidence in eight mixed Unit 6 cases
Connect equilibrium constraints and evidence in eight mixed Unit 7 cases
Connect acid–base assumptions and evidence in eight mixed Unit 8 cases
Connect free energy, equilibrium and electrochemistry in eight mixed Unit 9 cases
Save a science backup or import one
Science work is stored locally in this browser, separately from mathematics and AI. It does not sync automatically. Use this science-only backup; this checkout's older all-subject export does not include science.
A legacy file is available only when the complete snapshot fits the 36 MB limit. For larger snapshots, prepare a complete file set below; never discard notebooks to make a smaller file.
Matching imported notebook drafts replace their current drafts. Omitted lessons and known first attempts remain. Export your current work first if you want to retain both drafts.
Complete file sets and course backups
A file set can hold more work than one science file. Keep its manifest and every part together. Each file is limited to 36 MB. This format needs this version of LearnAI or a compatible newer version; older versions can use only the legacy single-file backup above.
The set includes every saved science course and global continuation at this moment. Later edits need a new export. A conflicting tab exports its own visible work, which may differ from saved work in another tab.
0 file(s) selected. File order and filenames do not determine identity. Missing, changed or conflicting parts block the entire restore; no good part is applied by itself.
Science storage: loading. No account or remote computation is required.