AQA GCSE Chemistry Paper 1h 2025 Mark Scheme

Get the official AQA GCSE Chemistry Paper 1 Higher Tier (8462/1H) **June 2025 mark scheme (Version 1.0 Final)** — the examiner-approved document used to award marks across all **100 marks** of the exam. It includes full answers, level descriptors, calculations, and detailed examiner guidance for every question.

The mark scheme begins with detailed examiner instructions on *pages 2–6*, including how AQA applies “best fit” marking for extended responses, awards method marks in calculations, handles errors carried forward (ecf), and credits alternative scientifically valid answers.

For *Question 1 (pages 7–9)*, accepted answers include the position of non-metals “towards the right and the top” of the periodic table, sodium’s electronic structure, and explanations that argon is unreactive because it has a full outer electron shell and a stable electronic structure.

Bonding and structure answers are covered in *Question 2 (pages 10–11)*. The mark scheme confirms the empirical formula **CaS**, explains ionic bonding in terms of electron transfer and ion formation, and provides indicative content for graphite, including giant covalent layers, hexagonal rings, delocalised electrons, and strong covalent bonds.

Extraction of metals and quantitative chemistry are assessed in *Question 3 (pages 12–14)*. Accepted responses identify tin oxide as the substance reduced because it loses oxygen, while the atom economy calculation gives **80%** for cadmium extraction. The mark scheme also lists key transition-metal properties such as high density, coloured compounds, and catalytic behaviour.

For halogens and Group 7 chemistry, *Question 4 (pages 15–16)* gives a predicted boiling point for chlorine of approximately **–34 °C**, identifies fluorine as a solid at –250 °C, and explains that halogen reactivity decreases down the group because outer electrons are further from the nucleus and more shielded. The balanced displacement equation is shown as **Br₂ + 2KI → I₂ + 2KBr**.

Atomic models and nanoparticles are covered in *Question 5 (pages 17–18)*. The mark scheme describes the plum pudding model as electrons embedded in a positively charged sphere, confirms that atoms are mostly empty space, and calculates the surface area-to-volume ratio of the nanoparticle as **5 : 1**.

Electrolysis and aluminium extraction appear in *Question 6 (pages 19–20)*. Accepted answers explain the strong electrostatic attraction between oppositely charged ions in aluminium oxide, identify **cryolite** as the added substance, and provide the half equation **2O²⁻ → O₂ + 4e⁻** for oxygen production.

Fuel cells, bonding, and energetics are examined in *Question 7 (pages 21–23)*. The mark scheme highlights advantages of hydrazine fuel cells, including easier storage as a liquid and higher voltage output. It also confirms the bond energy value **158 kJ/mol** for the calculation question and shows the correct hydrazine dot-and-cross diagram.

Acids, alkalis, and titrations are covered in *Question 8 (pages 24–27)*. The mark scheme identifies **OH⁻** as the ion in alkalis, suggests practical improvements such as using phenolphthalein instead of universal indicator, gives the burette reading as **24.70 cm³**, and calculates sodium hydroxide concentration as **0.960 mol/dm³**.

The final section, *Question 9 (pages 28–30)*, provides a full level-based method for preparing zinc iodide crystals using ethanol, filtration, and evaporation. The percentage yield calculation is confirmed as **78.9% (3 significant figures)**.

Use this mark scheme to accurately mark your answers, understand examiner expectations, and improve extended-response techniques. Pair it with the AQA 8462/1H May 2025 question paper for complete exam preparation.

This document is designed for GCSE Chemistry students preparing for the 2026 exam series, particularly Year 11 students studying the AQA 8462 Higher Tier specification, as well as resit candidates and independent learners.

It is also ideal for teachers, tutors, and revision providers who need accurate mark schemes for marking mock exams, standardising grading, and teaching exam technique. It supports detailed feedback across atomic structure, bonding, quantitative chemistry, electrolysis, and acids.