ChemSphere

AP & IB Chemistry, made visible

Nine units, nine simulators you can push and pull, practice questions that explain the wrong answers, and flashcards that remember what you keep missing.

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AP Chemistry

Following the College Board course framework, unit by unit, with each unit’s share of the exam.

  1. Unit 17–9% of exam

    Atomic Structure and Properties

    Unit 1 links the mole to real masses and builds the modern picture of the atom: isotopes, electron configurations and the Coulombic attractions that explain periodic trends. Nearly every later unit leans on mole conversions and on explaining properties with nuclear charge, distance and shielding.

    Electron configuration builder

  2. Unit 27–9% of exam

    Molecular and Ionic Compound Structure and Properties

    Unit 2 explains how atoms are held together, whether by ionic, covalent or metallic bonding, and how to draw and use Lewis structures. VSEPR shapes, resonance and formal charge let you predict a molecule's geometry and polarity, which sets up the intermolecular forces in Unit 3.

    VSEPR shape explorer

  3. Unit 318–22% of exam

    Intermolecular Forces and Properties

    Unit 3 is the heaviest-weighted unit. It explains how forces between particles control boiling points, solubility and the behavior of gases, solutions and solids. It also covers how matter interacts with light, from spectroscopy to the Beer–Lambert law used in lab analysis.

    Gas particles in a box

  4. Unit 47–9% of exam

    Chemical Reactions

    Unit 4 is about writing reactions correctly and using them quantitatively. You will balance and write net ionic equations, use stoichiometry and titration to connect amounts, and classify reactions as precipitation, acid–base or redox. These are the working tools for every calculation later in the course.

    Limiting reactant lab

  5. Unit 57–9% of exam

    Kinetics

    Unit 5 asks how fast reactions go and why. You will find rate laws from experimental data, use integrated rate laws and half-lives, and connect rates to collisions, activation energy and step-by-step mechanisms. Catalysts, which speed up reactions without being used up, tie the ideas together.

    Collision and rate simulator

  6. Unit 67–9% of exam

    Thermodynamics

    Unit 6 (thermochemistry) tracks the energy that flows as heat during physical and chemical changes. You will use calorimetry to measure heat, then find enthalpies of reaction from bond enthalpies, enthalpies of formation and Hess's law. The skills carry straight into Unit 9's look at entropy and free energy.

    Calorimetry and energy diagrams

  7. Unit 77–9% of exam

    Equilibrium

    Unit 7 covers reversible reactions that reach a dynamic balance in which the forward and reverse rates are equal. You will write and manipulate K expressions, compare Q with K to predict how a reaction shifts, calculate equilibrium concentrations and apply Le Châtelier's principle. It ends with solubility equilibria (Ksp), which sets up Unit 8.

    Le Chatelier's principle

  8. Unit 811–15% of exam

    Acids and Bases

    Unit 8 applies equilibrium to proton transfer. You will calculate pH for strong and weak acids and bases, read titration curves, and explain how buffers resist pH change. It also links acid strength to molecular structure, and it is one of the most heavily tested units on the exam.

    Titration simulator

  9. Unit 97–9% of exam

    Applications of Thermodynamics

    Unit 9 asks whether a process is thermodynamically favorable, not just how much heat it releases. Entropy and Gibbs free energy connect to the equilibrium constant, and the same ideas power electrochemistry: galvanic cells that make electricity and electrolytic cells that use it.

    Galvanic cell builder

The simulator lab

Each one turns a unit’s central idea into something you can change and watch respond.

Taking IB Chemistry?

The IB Diploma Chemistry course (first assessment 2025) is organised into two interlinked strands, Structure (S1–S3) and Reactivity (R1–R3), taught in 150 hours at SL and 240 hours at HL, with HL students also studying additional higher level (AHL) content. Assessment is 80% external: Paper 1 (36%; Paper 1A multiple-choice questions and Paper 1B data-based questions linked to experimental work) and Paper 2 (44%; short-answer and extended-response questions), lasting 1 h 30 min each at SL and 2 h and 2 h 30 min at HL. The remaining 20% is the Internal Assessment, a 10-hour scientific investigation written up in at most 3,000 words.

Open the IB guide

AP exam day, decoded

  • Know the format: Section I is 60 multiple-choice questions in 90 minutes (50% of the score); Section II is 7 free-response questions in 105 minutes (50%): 3 long (10 points each) and 4 short (4 points each).

  • Pace the multiple choice at about 1.5 minutes per question. Skip and flag time sinks, and answer every question, because there is no penalty for guessing.

  • Use the reference materials you are given (the periodic table and the formulas-and-constants sheet) for values such as R, F, h and the integrated rate laws, but memorize the solubility rules, strong acids/bases and common ion charges, which are not provided.

  • Bring an approved calculator and check the College Board's current calculator policy for both sections. Older practice materials had a calculator-free multiple-choice section, so keep your mental math sharp anyway: many MCQs are built to be done by estimation (logs, powers of 10, simple ratios).

  • On free response, show the setup: write the equation, substitute values with units, then give the answer with units and reasonable significant figures. A correct answer with no work can lose points.

  • When asked to 'justify' or 'explain', name the specific particle-level reason (e.g., Coulombic attraction, hydrogen bonding, Q vs K, effective nuclear charge) and connect it to the observation. Restating the question earns nothing.

  • Expect lab-based questions: practise interpreting data tables and graphs and predicting whether an experimental error (spilled solid, wet buret, heat loss) makes a calculated result too high or too low, and why.

  • Budget about 20–23 minutes for each long FRQ and 7–9 minutes for each short one. Answer later parts even if an earlier part went wrong: using your earlier (wrong) value correctly can still earn credit.