Unit 1 · Physical Chemistry (AS & A Level)
The Complete Cambridge International AS & A Level Chemistry (9701) Guide · Cambridge International AS & A Level Chemistry (9701)Unit 1 · Physical Chemistry (AS & A Level)
- The Complete Cambridge International AS & A Level Chemistry (9701) Guide
- Cambridge International AS & A Level Chemistry (9701)
- 4 sections
Cambridge International does not publish a per-unit weighting for this exam. Exam structure (official): AS Level: Multiple Choice (75 min, 40 questions, 31%) · AS Level Structured Questions (75 min, 46%) · Advanced Practical Skills (120 min, 23%); A Level: Multiple Choice (75 min, 40 questions, 15.5%) · AS Level Structured Questions (75 min, 23%) · Advanced Practical Skills (120 min, 11.5%) · A Level Structured Questions (120 min, 38.5%) · Planning, Analysis And Evaluation (75 min, 11.5%). Be ready to carry the same unit skills and representations into a complete answer on every paper. Begin with the object being counted. Electrons determine ionic configuration, atoms determine formula ratios, molecules determine gas amount, and reacting particles determine collision frequency. Writing the species beside every amount prevents a numerical answer from drifting away from its chemical meaning.
- How Cambridge International AS & A Level Chemistry (9701) assesses this Cambridge International publishes no per-unit percentage for Cambridge International A Level Chemistry; Paper 1 accounts for 31% of the AS Level total and 15.5% of the A Level total. · AS Level: Multiple Choice (75 min, 40 questions, 31%) · AS Level Structured Questions (75 min, 46%) · Advanced Practical Skills (120 min, 23%) | A Level: Multiple Choice (75 min, 40 questions, 15.5%) · AS Level Structured Questions (75 min, 23%) · Advanced Practical Skills (120 min, 11.5%) · A Level Structured Questions (120 min, 38.5%) · Planning, Analysis And Evaluation (75 min, 11.5%) · show the model with a species-labeled conversion chain, a balanced equation with mole ratios, an energy, equilibrium, or rate relationship with units, a signed energy cycle or free-energy relation, paired reduction half-equations and a cell calculation, an equilibrium, buffer, or rate expression with powers and units
- Key skills Atomic Structure: Subatomic Particles, Isotopes, Electronic Configuration and Ionisation Energy, Stoichiometry: Relative Masses, the Mole, Formulas, Reacting Masses and Volumes, and the Ideal Gas Equation, Chemical Bonding: Electronegativity, Ionic, Covalent, Coordinate and Metallic Bonding, Dot-and-Cross Diagrams, Shapes of Molecules, Intermolecular Forces and Lattice Structures, Chemical Energetics: Enthalpy Changes, Bond Energies and Hess's Law, Redox Processes: Electron Transfer and Oxidation Numbers, Equilibria: Le Chatelier's Principle, Equilibrium Constants and Brønsted-Lowry Acids and Bases, Reaction Kinetics: Collision Theory, Activation Energy, the Boltzmann Distribution and Catalysts, Lattice Energy, Born-Haber Cycles and Enthalpies of Solution and Hydration (A Level), Entropy Change and Gibbs Free Energy Change (A Level), Electrolysis and Faraday Calculations (A Level), Standard Electrode Potentials, Cell Potentials and the Nernst Equation (A Level), Acid-Base Equilibria: pH, Ka, pKa, Kw and Buffer Solutions (A Level), Solubility Product, the Common Ion Effect and Partition Coefficients (A Level), Reaction Kinetics: Rate Equations, Orders of Reaction, Rate Constants, Mechanisms and Catalysis (A Level)
- How to study for Unit 1 This page turns a species-labeled conversion chain, a balanced equation with mole ratios, an energy, equilibrium, or rate relationship with units, a signed energy cycle or free-energy relation, paired reduction half-equations and a cell calculation, an equilibrium, buffer, or rate expression with powers and units into one route: Write the balanced equation, name the species attached to each value, and keep every unit visible..
- The organizing decision Choose the chemical species and quantity before converting mass, amount, concentration, gas volume, energy, or rate.
- What A Level adds Select the governing physical relationship and keep its sign, units, reaction direction, and conditions attached to the result. Topics: Lattice Energy, Born-Haber Cycles and Enthalpies of Solution and Hydration; Entropy Change and Gibbs Free Energy Change; Electrolysis and Faraday Calculations; Standard Electrode Potentials, Cell Potentials and the Nernst Equation; Acid-Base Equilibria: pH, Ka, pKa, Kw and Buffer Solutions; Solubility Product, the Common Ion Effect and Partition Coefficients; Reaction Kinetics: Rate Equations, Orders of Reaction, Rate Constants, Mechanisms and Catalysis.
What Cambridge International AS & A Level Chemistry (9701) Unit 1 covers
Use this map to connect each assessed skill to the relationship or representation that makes it visible.
Atomic Structure: Subatomic Particles, Isotopes, Electronic Configuration and Ionisation Energy
amount of substance; stoichiometric ratio; dynamic equilibrium02Stoichiometry: Relative Masses, the Mole, Formulas, Reacting Masses and Volumes, and the Ideal Gas Equation
amount of substance; stoichiometric ratio; dynamic equilibrium03Chemical Bonding: Electronegativity, Ionic, Covalent, Coordinate and Metallic Bonding, Dot-and-Cross Diagrams
amount of substance; stoichiometric ratio; dynamic equilibrium04Shapes of Molecules, Intermolecular Forces and Lattice Structures
amount of substance; stoichiometric ratio; dynamic equilibrium05Chemical Energetics: Enthalpy Changes, Bond Energies and Hess's Law
amount of substance; stoichiometric ratio; dynamic equilibrium06Redox Processes: Electron Transfer and Oxidation Numbers
amount of substance; stoichiometric ratio; dynamic equilibrium07Equilibria: Le Chatelier's Principle, Equilibrium Constants and Brønsted-Lowry Acids and Bases
amount of substance; stoichiometric ratio; dynamic equilibrium08Reaction Kinetics: Collision Theory, Activation Energy, the Boltzmann Distribution and Catalysts
amount of substance; stoichiometric ratio; dynamic equilibrium09Lattice Energy, Born-Haber Cycles and Enthalpies of Solution and Hydration (A Level)
Gibbs free energy; standard electrode potential; rate equation10Entropy Change and Gibbs Free Energy Change (A Level)
Gibbs free energy; standard electrode potential; rate equation11Electrolysis and Faraday Calculations (A Level)
Gibbs free energy; standard electrode potential; rate equation12Standard Electrode Potentials, Cell Potentials and the Nernst Equation (A Level)
Gibbs free energy; standard electrode potential; rate equation13Acid-Base Equilibria: pH, Ka, pKa, Kw and Buffer Solutions (A Level)
Gibbs free energy; standard electrode potential; rate equation14Solubility Product, the Common Ion Effect and Partition Coefficients (A Level)
Gibbs free energy; standard electrode potential; rate equation15Reaction Kinetics: Rate Equations, Orders of Reaction, Rate Constants, Mechanisms and Catalysis (A Level)
Gibbs free energy; standard electrode potential; rate equationCambridge International does not publish a per-unit weighting for this exam.
Official unit name and weighting: Cambridge International syllabus.
Physical chemistry: a particle-to-quantity map
Connect the published share to the unit model
Begin with the object being counted. Electrons determine ionic configuration, atoms determine formula ratios, molecules determine gas amount, and reacting particles determine collision frequency. Writing the species beside every amount prevents a numerical answer from drifting away from its chemical meaning.
Use a representation that preserves the governing evidence. An energy profile answers a different question from a Maxwell–Boltzmann distribution; an equilibrium expression excludes solids while a mole ratio begins with a balanced equation. Units reveal which representation is active.
The map below separates three recurring demands. Each row names why the idea is difficult and what a creditworthy response must make visible; it is a planning aid, not a prediction of question frequency.
A dependable calculation begins by balancing the equation and naming the chemical amount attached to every number. Convert masses, concentrations, volumes, and gas data to moles with consistent units; apply the stoichiometric ratio; test whether a reagent limits the reaction; and convert only then to the requested quantity. For energy work, define the target reaction and its sign before scaling or reversing component equations. For equilibrium work, write the expression first, omit species that do not belong, and distinguish initial data from equilibrium data. Finish by checking magnitude, dimensions, sign, chemical direction, and rounding. A complete numerical response keeps the conversion chain visible and ends with the requested species, condition, unit, and justified precision.
The decision that organizes this unit
Define the system and choose the route before calculating
Choose the chemical species and quantity before converting mass, amount, concentration, gas volume, energy, or rate.
Write the balanced equation, name the species attached to each value, and keep every unit visible.
Mechanism route and repair branches
Relationships to preserve
- Particles and amount is shown through species-labeled conversions and a balanced ratio.
- Energy and rate is shown through signed energy change, conditions, and collision reasoning.
- Equilibrium and redox is shown through correct expression, electron balance, and justified shift.
- Feasibility is shown through convert before δh − tδs.
- Electrochemistry is shown through keep reduction convention.
- Rate laws is shown through compare controlled trials.
Representations to read
- a species-labeled conversion chain
- a balanced equation with mole ratios
- an energy, equilibrium, or rate relationship with units
- a signed energy cycle or free-energy relation
- paired reduction half-equations and a cell calculation
- an equilibrium, buffer, or rate expression with powers and units
Branches to reject
- switching between mass, moles, concentration, and gas volume without naming the species
- using an energy profile to answer a particle-distribution question
- losing reaction direction or units during equilibrium and redox work
- combining entropy and enthalpy in incompatible energy units
- reversing reduction potentials or multiplying them when balancing electrons
- treating feasibility as evidence that a reaction is fast
| Key concept | Why it's hard | What scores |
|---|---|---|
| Particles and amount | Switching among mass, moles, concentration, and gas volume | Species-labeled conversions and a balanced ratio |
| Energy and rate | Separating thermodynamic change from kinetic pathway | Signed energy change, conditions, and collision reasoning |
| Equilibrium and redox | Tracking direction while conserving matter and charge | Correct expression, electron balance, and justified shift |
How Cambridge International AS & A Level Chemistry (9701) assesses Physical Chemistry (AS & A Level)
What a complete response must make visible
Match the task to evidence that a reader can audit, then check the most likely reasoning failure before finalizing the response.
| Task | Evidence to show | Hurdle |
|---|---|---|
| Atomic Structure: Subatomic Particles, Isotopes, Electronic Configuration and Ionisation Energy | amount of substance; stoichiometric ratio; dynamic equilibrium | switching between mass, moles, concentration, and gas volume without naming the species |
| Stoichiometry: Relative Masses, the Mole, Formulas, Reacting Masses and Volumes, and the Ideal Gas Equation | amount of substance; stoichiometric ratio; dynamic equilibrium | using an energy profile to answer a particle-distribution question |
| Chemical Bonding: Electronegativity, Ionic, Covalent, Coordinate and Metallic Bonding, Dot-and-Cross Diagrams | amount of substance; stoichiometric ratio; dynamic equilibrium | losing reaction direction or units during equilibrium and redox work |
| Shapes of Molecules, Intermolecular Forces and Lattice Structures | amount of substance; stoichiometric ratio; dynamic equilibrium | combining entropy and enthalpy in incompatible energy units |
| Chemical Energetics: Enthalpy Changes, Bond Energies and Hess's Law | amount of substance; stoichiometric ratio; dynamic equilibrium | reversing reduction potentials or multiplying them when balancing electrons |
| Redox Processes: Electron Transfer and Oxidation Numbers | amount of substance; stoichiometric ratio; dynamic equilibrium | treating feasibility as evidence that a reaction is fast |
| Equilibria: Le Chatelier's Principle, Equilibrium Constants and Brønsted-Lowry Acids and Bases | amount of substance; stoichiometric ratio; dynamic equilibrium | switching between mass, moles, concentration, and gas volume without naming the species |
| Reaction Kinetics: Collision Theory, Activation Energy, the Boltzmann Distribution and Catalysts | amount of substance; stoichiometric ratio; dynamic equilibrium | using an energy profile to answer a particle-distribution question |
| Lattice Energy, Born-Haber Cycles and Enthalpies of Solution and Hydration (A Level) | Gibbs free energy; standard electrode potential; rate equation | losing reaction direction or units during equilibrium and redox work |
| Entropy Change and Gibbs Free Energy Change (A Level) | Gibbs free energy; standard electrode potential; rate equation | combining entropy and enthalpy in incompatible energy units |
| Electrolysis and Faraday Calculations (A Level) | Gibbs free energy; standard electrode potential; rate equation | reversing reduction potentials or multiplying them when balancing electrons |
| Standard Electrode Potentials, Cell Potentials and the Nernst Equation (A Level) | Gibbs free energy; standard electrode potential; rate equation | treating feasibility as evidence that a reaction is fast |
| Acid-Base Equilibria: pH, Ka, pKa, Kw and Buffer Solutions (A Level) | Gibbs free energy; standard electrode potential; rate equation | switching between mass, moles, concentration, and gas volume without naming the species |
| Solubility Product, the Common Ion Effect and Partition Coefficients (A Level) | Gibbs free energy; standard electrode potential; rate equation | using an energy profile to answer a particle-distribution question |
| Reaction Kinetics: Rate Equations, Orders of Reaction, Rate Constants, Mechanisms and Catalysis (A Level) | Gibbs free energy; standard electrode potential; rate equation | losing reaction direction or units during equilibrium and redox work |
Carry a balanced ratio from mass to gas amount
Read each question as it appears on the exam paper, choose your answer, then tap it to see the feedback.
Practice 1: Carry a balanced ratio from mass to gas amount
A 5.00 g sample of pure calcium carbonate is heated completely: CaCO₃(s) → CaO(s) + CO₂(g). Mᵣ(CaCO₃) = 100.0 g mol⁻¹.
Calculate the amount of carbon dioxide formed and its volume at room conditions. Use a molar gas volume of 24.0 dm³ mol⁻¹ at these conditions.
[4]Show all necessary working.
Give the final volume in dm³ with appropriate precision.
A. 5.00 ÷ 100.0 = 0.0500 mol CaCO₃; the 1:1 ratio gives 0.0500 mol CO₂; volume = 0.0500 × 24.0 = 1.20 dm³.
✅ Correct! 😊 This labels each amount, applies the balanced 1:1 ratio and uses the stated conditional molar volume. The final value is in dm³ and has three significant figures.
B. 5.00 × 100.0 = 500 mol CaCO₃; volume = 500 × 24.0 = 12 000 dm³.
❌ Not quite 😭 Mass is converted to amount by dividing by molar mass, not multiplying. The huge result is also inconsistent with a five-gram sample.
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C. 5.00 ÷ 100.0 = 0.0500 mol CaCO₃; the ratio gives 0.100 mol CO₂; volume = 2.40 dm³.
❌ Not quite 😭 The amount conversion is correct, but the equation does not double the amount. One mole of CaCO₃ forms one mole of CO₂, so the gas amount remains 0.0500 mol.
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D. 5.00 ÷ 100.0 = 0.05 mol CO₂; volume = 0.05 ÷ 24.0 = 0.0021 dm³.
❌ Not quite 😭 Gas volume is amount multiplied by molar volume, as the units mol × dm³ mol⁻¹ show. This route also rounds the amount before the final calculation.
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Full explanation
- Step 1Convert the named solid to amount: n(CaCO₃) = 5.00 g ÷ 100.0 g mol⁻¹ = 0.0500 mol.
- Step 2The balanced equation shows a 1:1 ratio, so n(CO₂) = 0.0500 mol.
- Step 3At the stated conditions, V(CO₂) = 0.0500 mol × 24.0 dm³ mol⁻¹ = 1.20 dm³.
- Step 4Retain the condition and gas identity, and report the volume to three significant figures.
Practice 2: Determine a rate equation from controlled trials
For the reaction between A and B, initial-rate data are: trial 1, [A] = 0.100 mol dm⁻³, [B] = 0.100 mol dm⁻³, rate = 2.00 × 10⁻³ mol dm⁻³ s⁻¹; trial 2, 0.200, 0.100, 8.00 × 10⁻³; trial 3, 0.100, 0.200, 4.00 × 10⁻³.
Determine the order with respect to A and B, write the rate equation, and calculate the rate constant with its units.
[5]Use comparisons in which only one concentration changes.
Show all necessary working.
A. rate = k[A][B]; k = 0.200 dm³ mol⁻¹ s⁻¹
❌ Not quite 😭 Doubling A at constant B makes the rate four times larger, not twice as large. Treating A as first order loses the trial 1 to trial 2 evidence.
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B. rate = k[A]²[B]; k = 2.00 dm⁶ mol⁻² s⁻¹
✅ Correct! 😊 A doubling causes a fourfold rate change, so A is second order; doubling B doubles rate, so B is first order. Substitution into trial 1 gives the stated k and units.
C. rate = k[A][B]²; k = 2.00 dm⁶ mol⁻² s⁻¹
❌ Not quite 😭 This assigns the orders to the wrong reactants. Trial 1 to trial 3 shows that doubling B only doubles the rate, so B is first order.
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D. rate = k[A]²[B]; k = 2.00 mol dm⁻³ s⁻¹
❌ Not quite 😭 The rate equation and numerical value are correct, but the units belong to rate rather than k. Dimensional division by three concentration factors gives dm⁶ mol⁻² s⁻¹.
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Full explanation
- Step 1Compare trials 1 and 2: [A] doubles at constant [B], while rate quadruples, so the order in A is 2.
- Step 2Compare trials 1 and 3: [B] doubles at constant [A], while rate doubles, so the order in B is 1.
- Step 3Therefore rate = k[A]²[B]; using trial 1 gives k = 2.00 × 10⁻³ ÷ (0.100² × 0.100) = 2.00.
- Step 4Dimensional balance gives k the units dm⁶ mol⁻² s⁻¹.
Key terms for Unit 1: Physical Chemistry (AS & A Level)
Models, uses, and boundaries
- Amount
- Mass-to-amount and concentration relations share the mole as the conserved bridge. Use this amount when the question calls for the relationship described here.
- Dimension Chain
- The unit chain exposes both the stoichiometric basis and the final gas-volume unit. Use this dimension chain when the question calls for the relationship described here.
- Calorimetry
- The leading minus sign converts heat gained by the solution into heat released by the reaction. Use this calorimetry when the question calls for the relationship described here.
- Polarity
- Vector cancellation distinguishes polar bonds from the polarity of the whole molecule. Use this polarity when the question calls for the relationship described here.
- Mcq Check
- The decision filter names four independent ways an option can fail. Use this mcq check when the question calls for the relationship described here.
- Feasibility Map
- Free energy requires compatible units and absolute temperature. Use this feasibility map when the question calls for the relationship described here.
- Entropy
- The converted entropy term matches the enthalpy unit. Use this entropy when the question calls for the relationship described here.
- Nernst
- The quotient correction follows the standard cell potential. Use this nernst when the question calls for the relationship described here.
- Buffer
- The ratio preserves which partner is more abundant. Use this buffer when the question calls for the relationship described here.
- Rate Law
- Dimensional balance gives the rate-constant unit. Use this rate law when the question calls for the relationship described here.
Cambridge International AS & A Level Chemistry (9701) Unit 1 FAQ
How much of Cambridge International AS & A Level Chemistry (9701) does Unit 1 carry?
Cambridge International does not publish a per-unit weighting for this exam.
What is the first move on a Physical Chemistry (AS & A Level) problem?
Write the balanced equation, name the species attached to each value, and keep every unit visible.
Which relationships should I preserve?
Particles and amount is shown through species-labeled conversions and a balanced ratio. Energy and rate is shown through signed energy change, conditions, and collision reasoning. Equilibrium and redox is shown through correct expression, electron balance, and justified shift. Feasibility is shown through convert before δh − tδs. Electrochemistry is shown through keep reduction convention. Rate laws is shown through compare controlled trials.
Which representations should I practice?
Practice moving among a species-labeled conversion chain, a balanced equation with mole ratios, an energy, equilibrium, or rate relationship with units, a signed energy cycle or free-energy relation, paired reduction half-equations and a cell calculation, an equilibrium, buffer, or rate expression with powers and units.
What error should I check before submitting an answer?
Check for switching between mass, moles, concentration, and gas volume without naming the species; using an energy profile to answer a particle-distribution question; losing reaction direction or units during equilibrium and redox work; combining entropy and enthalpy in incompatible energy units; reversing reduction potentials or multiplying them when balancing electrons; treating feasibility as evidence that a reaction is fast.
Evidence workshop
Continue from the free model into complete practice
The full unit guide continues with the chapter’s worked examples, figures, scoring tables, and answer checks.
- Carry a balanced ratio from mass to gas amount
- Determine a molar enthalpy from calorimetry
- Translate bonding evidence into shape and property
- Use option families without inventing an official item
Full unit practice. Open the complete guide for the full evidence workshop and synthesis.
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Cambridge International does not publish a per-unit weighting for this exam.How to study Cambridge International AS & A Level Chemistry (9701) Unit 1
Start with the organizing decision
Before solving, restate the decision in operational terms: Choose the chemical species and quantity before converting mass, amount, concentration, gas volume, energy, or rate.. Your first written move should be to Write the balanced equation, name the species attached to each value, and keep every unit visible..
Practice the same idea in several representations
Rotate through a species-labeled conversion chain, a balanced equation with mole ratios, an energy, equilibrium, or rate relationship with units, a signed energy cycle or free-energy relation, paired reduction half-equations and a cell calculation, an equilibrium, buffer, or rate expression with powers and units. Use each representation to practice Atomic Structure: Subatomic Particles, Isotopes, Electronic Configuration and Ionisation Energy, Stoichiometry: Relative Masses, the Mole, Formulas, Reacting Masses and Volumes, and the Ideal Gas Equation, Chemical Bonding: Electronegativity, Ionic, Covalent, Coordinate and Metallic Bonding, Dot-and-Cross Diagrams, Shapes of Molecules, Intermolecular Forces and Lattice Structures, Chemical Energetics: Enthalpy Changes, Bond Energies and Hess's Law, Redox Processes: Electron Transfer and Oxidation Numbers, Equilibria: Le Chatelier's Principle, Equilibrium Constants and Brønsted-Lowry Acids and Bases, Reaction Kinetics: Collision Theory, Activation Energy, the Boltzmann Distribution and Catalysts, Lattice Energy, Born-Haber Cycles and Enthalpies of Solution and Hydration (A Level), Entropy Change and Gibbs Free Energy Change (A Level), Electrolysis and Faraday Calculations (A Level), Standard Electrode Potentials, Cell Potentials and the Nernst Equation (A Level), Acid-Base Equilibria: pH, Ka, pKa, Kw and Buffer Solutions (A Level), Solubility Product, the Common Ion Effect and Partition Coefficients (A Level), Reaction Kinetics: Rate Equations, Orders of Reaction, Rate Constants, Mechanisms and Catalysis (A Level), and explain what stays invariant when the surface form changes.
Turn each error into a repair check
After every attempt, audit the response for switching between mass, moles, concentration, and gas volume without naming the species; using an energy profile to answer a particle-distribution question; losing reaction direction or units during equilibrium and redox work; combining entropy and enthalpy in incompatible energy units; reversing reduction potentials or multiplying them when balancing electrons; treating feasibility as evidence that a reaction is fast. Then redo only the first step that made the reasoning diverge, keeping units, direction, and model conditions visible.
Confirm current course details in the official Cambridge International syllabus for the 2025-2027 administration.
Where to go next
Return to the Cambridge International AS & A Level Chemistry (9701) to see every unit and plan your revision.