Cambridge IGCSE Chemistry 0620 Exhaustive Study Notes 2026-2028

Official Overview of Cambridge IGCSE Chemistry 0620

The Cambridge IGCSE Chemistry 0620 syllabus is designed for examination in 2026, 2027, and 2028. Exams occur in the June and November series globally, with a March series available specifically in India. Cambridge International is a department of the University of Cambridge and provides a pathway for students aged $5$ to $19$. The organization is independently certified under ISO 9001:2015 for its quality management systems.

Strategic Foundations and Learner Attributes

Cambridge programmes focus on aligning curriculum, teaching, learning, and assessment to develop deep knowledge and conceptual understanding. The specific approach to Chemistry encourages learners to develop five key attributes:

• Confident: Interested in learning about science, questioning ideas, and utilizing scientific language for communication.
• Responsible: Working methodically and safely, whether independently or in collaboration.
• Reflective: Learning from experiences and showing interest in scientific issues affecting individuals, communities, and the environment.
• Innovative: Solving unfamiliar problems with confidence and creativity.
• Engaged: Curious about scientific principles and their real-world applications, with a keenness to develop scientific skills.

UK ENIC, the national agency for qualification recognition in the UK, has benchmarked Cambridge IGCSE and found it comparable to the standard of the UK GCSE. Candidates achieving grades $A*$ to $C$ are considered well-prepared for higher-level courses such as Cambridge International AS & A Level Chemistry.

Global Feedback and Recognition

• Christoph Guttentag, Dean of Undergraduate Admissions, Duke University, USA: "We think the Cambridge curriculum is superb preparation for university."
• Gary Tan, Head of Schools and CEO, Raffles Group of Schools, Indonesia: "The strength of Cambridge IGCSE qualifications is internationally recognised and has provided an international pathway for our students to continue their studies around the world."
• Managing Director of British School of Egypt BSE: "Cambridge IGCSE is one of the most sought-after and recognised qualifications in the world. It is very popular in Egypt because it provides the perfect preparation for success at advanced level programmes."
• Zhai Xiaoning, Deputy Principal, The High School Affiliated to Renmin University of China: "While studying Cambridge IGCSE and Cambridge International A Levels, students broaden their horizons through a global perspective and develop a lasting passion for learning."

Support Services for Educators

Cambridge provides a School Support Hub, a secure online site offering syllabuses, schemes of work, specimen papers, and teacher guides. Professional development is categorized into four levels:

• Introductory: An introduction to Cambridge programmes and qualifications.
• Extension: Developing understanding to build delivery confidence.
• Enrichment: Workshops aimed at transforming teaching approaches.
• Cambridge Professional Development Qualifications (PDQs): Practice-based programmes available at Certificate and Diploma levels.

Syllabus Aims

The educational purposes of this syllabus seek to enable students to:

• Acquire scientific knowledge and understanding of theories and practice.
• Develop experimental skills, including handling variables and laboratory safety.
• Use scientific data and evidence to solve problems and discuss method limitations.
• Communicate clearly using scientific terminology, notation, and conventions.
• Understand how scientific knowledge benefits people and the environment.
• Enjoy science and develop an interest that supports further study.

Assessment Objectives (AOs)

AO1: Knowledge with Understanding

Candidates must demonstrate knowledge and understanding of phenomena, facts, laws, definitions, concepts, theories, vocabulary, terminology, conventions (symbols, quantities, units), instruments, apparatus, and technological applications with their social, economic, and environmental implications.

AO2: Handling Information and Problem-Solving

Candidates must be able to locate, select, organize, and present information. They must translate information between forms, manipulate data, identify patterns/trends, report conclusions, and solve quantitative problems in unfamiliar contexts.

AO3: Experimental Skills and Investigations

Candidates must demonstrate the ability to select and use techniques and apparatus safely, plan experiments, record observations and measurements, interpret experimental data, and evaluate methods to suggest improvements.

Assessment Structure and Weighting

Candidate Eligibility and Grading

All candidates take three components and are eligible for grades $A*$ to $G$.

• Core Candidates: Usually expected to achieve grades $C$ to $G$. They take Paper 1, Paper 3, and either Paper 5 or 6.
• Extended Candidates: Target grades $A*$ to $C$. They take Paper 2, Paper 4, and either Paper 5 or 6.

Component Details

• Paper 1 (Core Multiple Choice): $45$ minutes, $40$ marks ($30\%$ weighting). Covers Core syllabus content.
• Paper 2 (Extended Multiple Choice): $45$ minutes, $40$ marks ($30\%$ weighting). Covers Core and Supplement content.
• Paper 3 (Core Theory): $1$ hour $15$ minutes, $80$ marks ($50\%$ weighting). Short-answer and structured questions.
• Paper 4 (Extended Theory): $1$ hour $15$ minutes, $80$ marks ($50\%$ weighting). Short-answer and structured questions.
• Paper 5 (Practical Test): $1$ hour $15$ minutes, $40$ marks ($20\%$ weighting). Requires laboratory experiments.
• Paper 6 (Alternative to Practical): $1$ hour, $40$ marks ($20\%$ weighting). Standard classroom-based assessment of practical skills.

AO Weighting by Component

• Papers 1 & 2: $63\%$ AO1, $37\%$ AO2.
• Papers 3 & 4: $63\%$ AO1, $37\%$ AO2.
• Papers 5 & 6: $100\%$ AO3.

Subject Content Section 1: States of Matter

• Properties: Distinction between solids, liquids, and gases based on particle separation, arrangement, and motion.
• Changes of State: Melting, boiling, evaporating, freezing, and condensing.
• Gas Volume: Effects of temperature and pressure on gas volume.
• Kinetic Particle Theory: Explanation of state changes and volume behavior; interpretation of heating and cooling curves.
• Diffusion: Explanation in terms of kinetic theory and the effect of relative molecular mass ($M_r$) on the rate of gas diffusion.

Subject Content Section 2: Atoms, Elements, and Compounds

2.1 Elements, Compounds, and Mixtures

• Differences between elements, compounds, and mixtures.

2.2 Atomic Structure

• Atom structure: central nucleus with protons and neutrons, surrounded by electrons in shells.
• Relative charges and masses: Proton ($+1$, $1$), Neutron ($0$, $1$), Electron ($-1$, $\frac{1}{1840}$ approx).
• Proton number (atomic number): Number of protons in the nucleus.
• Mass number (nucleon number): Total number of protons and neutrons.
• Electronic Configuration: For proton numbers $1$ to $20$ (e.g., $2,8,3$ for Aluminium).
• Group/Period Trends: Group number equals outer shell electrons ($I$ to $VII$); Period number equals occupied shells; Group $VIII$ noble gases have full outer shells.

2.3 Isotopes

• Definition: Atoms of the same element with same protons but different neutrons.
• Chemical properties remain the same due to identical electronic configurations.
• Relative Atomic Mass ($A_r$): Calculated from isotope masses and abundances.

2.4 Ions and Ionic Bonding

• Cations: Positive ions. Anions: Negative ions.
• Ionic Bond: Strong electrostatic attraction between oppositely charged ions.
• Structure: Giant lattice of alternating positive and negative ions.
• Properties: High melting/boiling points; conduct electricity when aqueous or molten, but not when solid.

2.5 Simple Molecules and Covalent Bonds

• Covalent Bond: Shared pair of electrons leading to noble gas configurations.
• Molecules to know: $H_2$, $Cl_2$, $H_2O$, $CH_4$, $NH_3$, $HCl$, $CH_3OH$, $C_2H_4$, $O_2$, $CO_2$, $N_2$.
• Properties: Low melting/boiling points (due to weak intermolecular forces); poor electrical conductivity.

2.6 Giant Covalent Structures

• Graphite: Used as lubricant and electrode; structure allows conductivity and sliding layers.
• Diamond: Used in cutting tools; high hardness due to tetrahedral structure.
• Silicon(IV) oxide ($SiO_2$): Similar properties and structure to diamond.

2.7 Metallic Bonding

• Electrostatic attraction between positive ions in a giant lattice and a 'sea' of delocalised electrons.
• Properties: Good electrical conductivity, malleability, and ductility.

Subject Content Section 3: Stoichiometry

• Formulae: Deduction from models; word and symbol equations with state symbols ($s, l, g, aq$).
• Empirical Formula: Simplest whole number ratio of atoms/ions.
• Molecular Formula: Actual number and type of atoms in one molecule.
• Relative Molecular Mass ($M_r$): Sum of $A_r$; Relative Formula Mass ($M_r$) for ionic compounds.
• The Mole: Unit for amount of substance; contains Avogadro constant ($6.02 \times 10^{23}$) particles.
• Molar Gas Volume: Taken as $24\,dm^3$ at room temperature and pressure ($r.t.p.$).
• Equations:
  • $\text{Amount of substance (mol)} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}}$
  • $\text{Concentration} = \text{g/dm}^3 \text{ or } \text{mol/dm}^3$
• Yield and Purity: Calculation of percentage yield, percentage composition by mass, and percentage purity.

Subject Content Section 4: Electrochemistry

• Electrolysis: Decomposition of ionic compounds (molten or aqueous) by electric current.
• Components: Anode (positive), Cathode (negative), Electrolyte (substance undergoing electrolysis).
• Movement: Electrons move in the external circuit; ions move in the electrolyte.
• Specific Electrolysis Cases:
  • Molten lead(II) bromide: Lead at cathode ($Pb^{2+} + 2e^- \rightarrow Pb$), Bromine at anode ($2Br^- \rightarrow Br_2 + 2e^-$).
  • Concentrated aqueous sodium chloride: Hydrogen at cathode, Chlorine at anode.
  • Dilute sulfuric acid: Hydrogen at cathode, Oxygen at anode.
  • Aqueous copper(II) sulfate: Products depend on whether carbon/graphite or copper electrodes are used.
• Electroplating: Used to improve appearance and corrosion resistance.
• Hydrogen-Oxygen Fuel Cells: Uses hydrogen and oxygen to produce electricity with water as the only product.

Subject Content Section 5: Chemical Energetics

• Exothermic: Transfers thermal energy to surroundings ($+\text{temperature}$, $-\Delta H$).
• Endothermic: Takes in thermal energy from surroundings ($-\text{temperature}$, $+\Delta H$).
• Activation Energy ($E_a$): Minimum energy for colliding particles to react.
• Bond Energies: Bond breaking is endothermic; bond making is exothermic.
• $\Delta H = \text{energy absorbed to break bonds} - \text{energy released making bonds}$

Subject Content Section 6: Chemical Reactions

6.2 Rate of Reaction

• Factors: Concentration, pressure, surface area, temperature, and catalysts.
• Collision Theory: Explains rates in terms of collision frequency and kinetic energy.
• Catalysts: Increase rate by lowering activation energy ($E_a$) while remaining unchanged.

6.3 Reversible Reactions and Equilibrium

• Equilibrium: Rates of forward and reverse reactions are equal; concentrations remain constant in a closed system.
• Haber Process (Ammonia):
  • $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$
  • Conditions: $450\,^{\circ}C$, $20\,000\,kPa$ ($200\,atm$), iron catalyst.
• Contact Process (Sulfur Trioxide):
  • $2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)$
  • Conditions: $450\,^{\circ}C$, $200\,kPa$ ($2\,atm$), vanadium(V) oxide catalyst.

6.4 Redox

• Oxidation: Gain of oxygen, loss of electrons, or increase in oxidation number.
• Reduction: Loss of oxygen, gain of electrons, or decrease in oxidation number.
• Tests: Acidified aqueous potassium manganate(VII) (purple to colourless); aqueous potassium iodide (colourless to brown).
• Agents: Oxidising agent reduces itself; reducing agent oxidises itself.

Subject Content Section 7: Acids, Bases, and Salts

• Acids: Proton donors ($H^+$ source in water). Bases: Proton acceptors (oxides/hydroxides).
• Alkalis: Soluble bases ($OH^-$ source in water).
• Indicators:
  • Thymolphthalein: Colourless (acid) to blue (alkali).
  • Methyl orange: Red (acid) to yellow (alkali).
• Neutralisation: $H^+(aq) + OH^-(aq) \rightarrow H_2O(l)$
• Strength: Strong acids (e.g., $HCl$) dissociate completely; weak acids (e.g., $CH_3COOH$) dissociate partially.
• Amphoteric Oxides: React with both acids and bases (e.g., $Al_2O_3$, $ZnO$).
• Solubility Rules:
  • All Sodium, Potassium, Ammonium, and Nitrate salts are soluble.
  • Chlorides are soluble except Lead and Silver.
  • Sulfates are soluble except Barium, Calcium, and Lead.
  • Carbonates are insoluble except Na, K, and $\text{NH}_4$.
  • Hydroxides are insoluble except Na, K, $\text{NH}_4$, and Ca (partially).

Subject Content Section 8: The Periodic Table

• Arrangement: Groups (vertical columns) and Periods (horizontal rows) by increasing proton number.
• Group I (Alkali Metals): Li, Na, K. Trends down: decreasing melting point, increasing density, increasing reactivity.
• Group VII (Halogens): Diatomic non-metals.
  • Chlorine: Pale yellow-green gas.
  • Bromine: Red-brown liquid.
  • Iodine: Grey-black solid.
  • Trends down: increasing density, decreasing reactivity.
• Transition Elements: High density, high melting points, form coloured compounds, act as catalysts, variable oxidation numbers (e.g., $Fe^{2+}, Fe^{3+}$).
• Group VIII (Noble Gases): Unreactive monatomic gases with full shells.

Subject Content Section 9: Metals

• Uses:
  • Aluminium: Aircraft (low density), food containers (corrosion resistance), cables (low density/conductivity).
  • Copper: Wiring (ductility/conductivity).
• Alloys: Mixtures of metals with other elements (e.g., Brass = Copper + Zinc; Stainless Steel = Iron + Chromium + Nickel + Carbon). Harder than pure metals because different sized atoms prevent layers sliding.
• Reactivity Series: K, Na, Ca, Mg, Al, C, Zn, Fe, H, Cu, Ag, Au.
• Corrosion: Rust requires water and oxygen to form hydrated iron(III) oxide. Prevention via barriers (paint, plastic) or sacrificial protection (Galvanising with Zinc).
• Extraction:
  • Iron (Blast Furnace): Iron(III) oxide reduced by carbon monoxide.
    • $C + O_2 \rightarrow CO_2$
    • $C + CO_2 \rightarrow 2CO$
    • $Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$
    • $CaCO_3 \rightarrow CaO + CO_2$
    • $CaO + SiO_2 \rightarrow CaSiO_3$
  • Aluminium: Electrolysis of purified bauxite in molten cryolite; carbon anodes require replacement.

Subject Content Section 10: Chemistry of the Environment

• Water: Tests via anhydrous cobalt(II) chloride (blue to pink) or anhydrous copper(II) sulfate (white to blue). Distilled water is preferred in labs for purity. Treatment includes sedimentation, filtration, carbon use, and chlorination.
• Fertilisers: NPK fertilisers provide Nitrogen, Phosphorus, and Potassium.
• Air: $78\%$ Nitrogen, $21\%$ Oxygen. Pollutants include $CO_2$ (complete combustion), $CO$ (toxic, incomplete combustion), Methane (decomposition/digestion), Oxides of Nitrogen (car engines), Sulfur Dioxide (fossil fuels).
• Photosynthesis: $6CO_2 + 6H_2O \rightarrow C_{12}H_{12}O_6 + 6O_2$ (light/chlorophyll).
• Strategies: Planting trees, catalytic converters ($2CO + 2NO \rightarrow 2CO_2 + N_2$), and flue gas desulfurisation ($CaO$).

Subject Content Section 11: Organic Chemistry

• Homologous Series: Family of compounds with same functional group and general formula; differ by $-CH_2-$ unit.
• Alkanes ($C_nH_{2n+2}$): Saturated hydrocarbons. Single bonds. Undergo substitution with chlorine (requires UV light).
• Alkenes ($C_nH_{2n}$): Unsaturated hydrocarbons ($C=C$ bond). Tested with bromine water (orange to colourless). Manufactured by cracking larger alkanes.
• Alcohols ($C_nH_{2n+1}OH$): Manufactured by fermentation of glucose ($25\text{--}35\,^{\circ}C$, yeast, no oxygen) or catalytic addition of steam to ethene ($300\,^{\circ}C$, $6000\,kPa$, acid catalyst).
• Carboxylic Acids ($C_nH_{2n+1}COOH$): Ethanoic acid produced by bacterial oxidation of ethanol or via acidified potassium manganate(VII).
• Polymers:
  • Addition: Poly(ethene).
  • Condensation: Nylon (polyamide) and PET (polyester).
  • Proteins: Natural polyamides from amino acid monomers.

Qualitative Analysis Notes: Tests

Anions

• Carbonate ($CO_3^{2-}$): Add dilute acid; effervescence, $CO_2$ produced.
• Chloride ($Cl^-$): Acidify with nitric acid, add silver nitrate; white ppt.
• Bromide ($Br^-$): Acidify with nitric acid, add silver nitrate; cream ppt.
• Iodide ($I^-$): Acidify with nitric acid, add silver nitrate; yellow ppt.
• Sulfate ($SO_4^{2-}$): Acidify with nitric acid, add barium nitrate; white ppt.
• Nitrate ($NO_3^-$): Sodium hydroxide + aluminium foil; warm; ammonia produced.
• Sulfite ($SO_3^{2-}$): Acidified potassium manganate(VII) turns purple to colourless.

Cations (Aqueous Sodium Hydroxide / Ammonia)

• Aluminium ($Al^{3+}$): White ppt., soluble in excess NaOH; insoluble in excess Ammonia.
• Ammonium ($NH_4^+$): Ammonia produced on warming with NaOH.
• Calcium ($Ca^{2+}$): White ppt., insoluble in excess NaOH; no ppt. with Ammonia.
• Copper(II) ($Cu^{2+}$): Light blue ppt., insoluble in excess NaOH; soluble in excess Ammonia (dark blue solution).
• Iron(II) ($Fe^{2+}$): Green ppt., insoluble in both; turns brown on standing.
• Iron(III) ($Fe^{3+}$): Red-brown ppt., insoluble in both.
• Zinc ($Zn^{2+}$): White ppt., soluble in excess in both.

Gas Tests

• Ammonia ($NH_3$): Damp red litmus turns blue.
• Chlorine ($Cl_2$): Bleaches damp litmus.
• Hydrogen ($H_2$): 'Pops' with lighted splint.
• Oxygen ($O_2$): Relights glowing splint.
• Sulfur Dioxide ($SO_2$): Turns acidified potassium manganate(VII) purple to colourless.

Flame Tests

• Lithium ($Li^+$): Red.
• Sodium ($Na^+$): Yellow.
• Potassium ($K^+$): Lilac.
• Calcium ($Ca^{2+}$): Orange-red.
• Barium ($Ba^{2+}$): Light green.
• Copper(II) ($Cu^{2+}$): Blue-green.

Laboratory Reagent Preparation

• Dilute Hydrochloric Acid ($1.0\,mol/dm^3$): Dilute $85\,cm^3$ of concentrated ($35\text{--}37\%$) $HCl$ to $1\,dm^3$.
• Dilute Sulfuric Acid ($0.5\,mol/dm^3$): Cautiously pour $28\,cm^3$ of concentrated ($98\%$) $H_2SO_4$ into $500\,cm^3$ distilled water, then make up to $1\,dm^3$.
• Limewater: Saturated aqueous calcium hydroxide, $Ca(OH)_2$.
• Methyl Orange Indicator: pH range $3.1\text{--}4.4$.
• Thymolphthalein Indicator: pH range $9.3\text{--}10.5$.

Mathematical and Data Requirements

• Algebra: Solve equations, use direct and inverse proportion, substitute values.
• Geometry: Understand circle variables (radius, etc.) and convert units ($cm^3$ to $dm^3$, $mg\text{--}g\text{--}kg$, $J\text{--}kJ$, $Pa\text{--}kPa$).
• Graphs: Plot axes, select scales, use best-fit lines (straight or curve). Extrapolate and interpolate. Gradient calculation ($Extended$) via tangents.
• Conventions: Decimal markers are dots. Spaces separate digits ($10\,000$ is $10\ 000$).
• Significant Figures: Measured data sig figs reflect instrument precision. Calculated data should match the least number of sig figs in raw data used.

Command Words for Examinations

• Calculate: Work out from given facts or figures.
• Compare: Identify similarities and differences.
• Deduce: Conclude from available information.
• Define: Give precise meaning.
• Describe: State points of a topic; give characteristics.
• Explain: Set out purposes or reasons; say why/how.
• Identify: Name or select.
• State: Express in clear terms.
• Suggest: Apply knowledge to proposals where various valid responses exist.