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Cambridge IGCSE Chemistry 0620 Syllabus (2023-2025) Answers

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Cambridge IGCSE Chemistry 0620 Syllabus (2023-2025) Answers

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Summary: Complete point-form answers to the Cambridge IGCSE Chemistry 0620 syllabus (2023-2025). Keywords are linked to their dedicated study pages for exam-focused revision. Tags: answers igcse chemistry syllabus revision Created: 2026-08-06

1 States of Matter

1.1 Solids, Liquids and Gases

Core:

  1. Distinguishing properties of solids, liquids and gases:

  2. Structures in terms of particle separation, arrangement and motion:

  3. Changes of state: melting, boiling, evaporating, freezing and condensing:

  4. Effects of temperature and pressure on the volume of a gas:

Supplement:

  1. Changes of state in terms of kinetic particle theory, including heating and cooling curves:

  2. Effects of temperature and pressure on gas volume via kinetic particle theory:

    • Temperature: heating gives gas particles more kinetic energy → move faster → collide with container walls with greater force and frequency → volume increases to maintain constant pressure
    • Pressure: increasing external pressure forces gas particles closer together → reduces space between them → decreases volume

1.2 Diffusion

Core:

  1. Diffusion in terms of kinetic particle theory:

Supplement:

  1. Effect of relative molecular mass on the rate of diffusion of gases:

2 Atoms, Elements and Compounds

2.1 Elements, Compounds and Mixtures

Core:

  1. Differences between elements, compounds and mixtures:

2.2 Atomic Structure and the Periodic Table

Core:

  1. Structure of the atom:

  2. Relative charges and masses of subatomic particles:

  3. atomic number:

  4. nucleon number:

  5. Electronic configuration of elements and ions (proton numbers 1–20):

  6. Periodic Table trends:

2.3 Isotopes

Core:

  1. Isotopes definition:

  2. Nuclide notation:

    • Written as ᴬᶻX where A = mass number, Z = atomic number
    • e.g. ¹²₆C means 6 protons, 6 neutrons; ³⁵₁₇Cl⁻ means 17 protons, 18 neutrons, 18 electrons

Supplement:

  1. Isotopes — same chemical properties:

  2. Relative atomic mass calculation:

    • Aᵣ = Σ (isotopic mass × % abundance) ÷ 100
    • Takes into account all naturally occurring isotopes and their relative abundances
    • e.g. for chlorine: Aᵣ = (35 × 75 + 37 × 25) ÷ 100 = 35.5

2.4 Ions and Ionic Bonds

Core:

  1. Formation of positive ions (cations) and negative ions (anions):

    • Cations: formed when an atom loses one or more electrons → positive charge
      • Metals (Groups I–III) tend to lose electrons
      • e.g. Na → Na⁺ + e⁻, Mg → Mg²⁺ + 2e⁻
    • Anions: formed when an atom gains one or more electrons → negative charge
      • Non-metals (Groups V–VII) tend to gain electrons
      • e.g. Cl + e⁻ → Cl⁻, O + 2e⁻ → O²⁻

  2. Ionic bond definition:

  3. Formation of ionic bonds between Group I and Group VII elements:

    • Group I metal loses 1 electron → 1+ ion
    • Group VII non-metal gains 1 electron → 1− ion
    • Use dot-and-cross diagrams:
      • e.g. NaCl: Na donates 1 electron to Cl → Na⁺ and Cl⁻
      • Show outer electrons as dots (one element) and crosses (other element)

  4. Properties of ionic compounds:

Supplement:

  1. Giant ionic lattice structure:

    • Regular arrangement of alternating positive and negative ions
    • e.g. NaCl forms a cubic lattice with each Na⁺ surrounded by 6 Cl⁻ (and vice versa)
    • Held together by strong electrostatic forces in all directions

  2. Formation of ionic bonds between metals and non-metals:

  3. Explain properties of ionic compounds in terms of structure and bonding:

2.5 Simple Molecules and Covalent Bonds

Core:

  1. Covalent bond definition:

  2. Formation of covalent bonds in simple molecules:

    • Using dot-and-cross diagrams:
    • H₂: H—H (single bond, each H shares 1 electron → 2 in outer shell)
    • Cl₂: Cl—Cl (single bond, each Cl shares 1 electron → 8 in outer shell)
    • H₂O: H—O—H (two single bonds, O shares 2 electrons → 8, each H gets 2)
    • CH₄: C with 4 single bonds to 4 H atoms (C shares 4 electrons → 8)
    • NH₃: N with 3 single bonds to 3 H atoms + 1 lone pair
    • HCl: H—Cl (single bond)

  3. Properties of simple molecular compounds:

Supplement:

  1. Formation of covalent bonds in more simple molecules:

    • CH₃OH: C with 3 single bonds to H + 1 single bond to O; O with single bond to H + 2 lone pairs
    • C₂H₄: C=C double bond, each C also bonded to 2 H atoms
    • O₂: O=O (double bond, each O shares 2 electrons)
    • CO₂: O=C=O (two double bonds)
    • N₂: N≡N (triple bond, each N shares 3 electrons)

  2. Explain properties of simple molecular compounds in terms of structure and bonding:

2.6 Giant Covalent Structures

Core:

  1. Giant covalent structures of graphite and diamond:

  2. Relate structures of graphite and diamond to their uses:

Supplement:

  1. Giant covalent structure of silicon(IV) oxide, SiO₂:

    • Similar to diamond: each Si atom bonded to 4 O atoms, each O bonded to 2 Si atoms
    • Forms a continuous 3D tetrahedral giant lattice
    • Overall formula SiO₂ (not SiO₂ molecules — the formula represents the ratio)

  2. Similarity in properties between diamond and silicon(IV) oxide:

2.7 Metallic Bonding

Supplement:

  1. Metallic bonding description:

  2. Explain properties of metals in terms of structure and bonding:

3 Stoichiometry

3.1 Formulae

Core:

  1. Formulae of elements and compounds in the subject content:

  2. Molecular formula:

    • Number and type of different atoms in one molecule
    • e.g. C₂H₆ has 2 carbon atoms and 6 hydrogen atoms in one molecule

  3. Deduce formula from diagram/model:

    • Count number of each type of atom present
    • Write as ratio → simplify if needed
    • e.g. model showing 2 H and 1 O → H₂O

  4. Word and symbol equations with state symbols:

    • State symbols: (s) solid, (l) liquid, (g) gas, (aq) aqueous (dissolved in water)
    • e.g. 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)

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