Principles of Chemistry

Worked examples (4)

• 1Particle arrangement → bulk properties (6 marks, Paper 1)
• 2Heating curve plateau (4 marks, Paper 1)
• 3Predicting and explaining gas diffusion rates (4 marks, Paper 1)
• 4Evaporation vs boiling (5 marks, Paper 2)

Model answers (4)

• ✓Model answer — 4CH1/1C-style 6-mark extended response — adapted from Edexcel sample assessments
• ✓Model answer — 4CH1/1CR-style — heating/cooling curve interpretation
• ✓Model answer — 4CH1/2C-style — practical diffusion of bromine
• ✓Model answer — 4CH1/2C-style short response

Worked examples (4)

• 1Distinguishing element, compound and mixture (5 marks, Paper 1)
• 2Fractional distillation of ethanol from water (6 marks, Paper 1)
• 3Calculating Rf in paper chromatography (4 marks, Paper 1)
• 4Pure substance vs mixture by melting point (4 marks, Paper 1)

Model answers (4)

• ✓Model answer — 4CH1/1C-style 6-mark separation question — adapted from Edexcel sample assessments
• ✓Model answer — 4CH1/2C-style — paper chromatography practical
• ✓Model answer — 4CH1/1C-style — purity / boiling point
• ✓Model answer — 4CH1/1CR-style — comparison response

Worked examples (4)

• 1Particles in an atom from $^A_Z X$ notation (4 marks, Paper 1)
• 2Relative atomic mass from isotopic abundance (4 marks, Paper 1)
• 3Electron configuration and the periodic table (4 marks, Paper 1)
• 4Identifying isotopes (3 marks, Paper 1)

Model answers (4)

• ✓Model answer — 4CH1/1C-style — atomic structure overview
• ✓Model answer — 4CH1/2C-style — isotopes
• ✓Model answer — 4CH1/2C-style — reverse Ar calculation
• ✓Model answer — 4CH1/1C-style — electron configuration

Worked examples (7)

• 1Balancing a chemical equation (3 marks, Paper 1)
• 2Mass to moles using $n = m / M_r$ (3 marks, Paper 1)
• 3Reacting mass (stoichiometry) (5 marks, Paper 1)
• 4Gas volume at rtp from moles (3 marks, Paper 1)
• 5Concentration of a solution (4 marks, Paper 1)
• 6Empirical formula from percentage composition (5 marks, Paper 2)
• 7Percentage yield and atom economy (5 marks, Paper 2)

Model answers (4)

• ✓Model answer — 4CH1/1C-style — balancing equations
• ✓Model answer — 4CH1/2C-style — moles and Avogadro
• ✓Model answer — 4CH1/2C-style — titration / concentration
• ✓Model answer — 4CH1/2C-style — yield reasons

Worked examples (4)

• 1Forming an ionic bond between Na and Cl (5 marks, Paper 1)
• 2Comparing melting points (5 marks, Paper 1)
• 3Conductivity of ionic compounds (4 marks, Paper 1)
• 4Writing the formula of aluminium oxide from ion charges (4 marks, Paper 1)

Model answers (4)

• ✓Model answer — 4CH1/1C-style — ionic properties extended response
• ✓Model answer — 4CH1/2C-style — dot-and-cross diagram for Na₂O
• ✓Model answer — 4CH1/2C-style — ion charges from periodic table
• ✓Model answer — 4CH1/2C-style — extended explanation

Worked examples (4)

• 1Describing a covalent bond using H₂ (4 marks, Paper 1)
• 2Dot-and-cross diagram for CO₂ — double bonds (4 marks, Paper 1)
• 3Comparing melting points of methane and diamond (5 marks, Paper 1)
• 4Why graphite conducts but diamond does not (6 marks, Paper 1)

Model answers (4)

• ✓Model answer — 4CH1/1C-style — covalent bond definition + Cl₂
• ✓Model answer — 4CH1/2C-style — multiple small-molecule dot-and-cross
• ✓Model answer — 4CH1/2C-style — properties of simple molecular substances
• ✓Model answer — 4CH1/2C-style — modern carbon allotropes

Worked examples (4)

• 1Defining and describing a metallic bond (4 marks, Paper 1)
• 2Explaining metallic conductivity and malleability (6 marks, Paper 1)
• 3Why metals have high melting points (3 marks, Paper 1)
• 4Why alloys are harder than the pure metal (4 marks, Paper 1)

Model answers (4)

• ✓Model answer — 4CH1/2C-style — metallic property explanations
• ✓Model answer — 4CH1/2C-style — identifying bonding from observations
• ✓Model answer — 4CH1/2C-style — alloys with worked examples
• ✓Model answer — 4CH1/2C-style — thermal conductivity

Worked examples (4)

• 1Electrolysis of molten lead(II) bromide (5 marks, Paper 1)
• 2Electrolysis of sodium chloride solution (brine) (6 marks, Paper 1)
• 3Calculating mass of copper deposited from Q = It (6 marks, Paper 2)
• 4Extraction of aluminium by electrolysis (6 marks, Paper 1)

Model answers (4)

• ✓Model answer — 4CH1/1C-style — electrolysis definition + apparatus
• ✓Model answer — 4CH1/2C-style — rules for aqueous electrolysis
• ✓Model answer — 4CH1/2C-style — copper purification
• ✓Model answer — 4CH1/2C-style — electroplating

Worked examples (4)

• 1How the modern periodic table is arranged (4 marks, Paper 1)
• 2Trend in reactivity DOWN Group 1 (5 marks, Paper 1)
• 3Trend in reactivity DOWN Group 7 (5 marks, Paper 1)
• 4Properties of transition metals (4 marks, Paper 1)

Model answers (4)

• ✓Model answer — 4CH1/2C-style — Mendeleev and history
• ✓Model answer — 4CH1/2C-style — noble gases
• ✓Model answer — 4CH1/2C-style — halogen displacement
• ✓Model answer — 4CH1/2C-style — using the periodic table to predict properties