AQA GCSE Combined Science: Trilogy — Chemistry Paper 1 (Higher Tier)

Total marks: 70 · Duration: 75 minutes · Tier: higher

Instructions to candidates

Answer all questions in the spaces provided.
You are expected to use a calculator and a copy of the periodic table.
This paper covers Topics 8–12: Atomic Structure and the Periodic Table, Bonding, Quantitative Chemistry, Chemical Changes, and Energy Changes.
The maximum mark for this paper is 70. The marks for each question are shown in brackets.

Paper

Section A — Multiple Choice (5 marks)

1. An atom has 11 protons, 12 neutrons and 11 electrons. Its mass number is: (1 mark) A) 11 B) 12 C) 22 D) 23

2. Which type of bonding occurs between a metal and a non-metal? (1 mark) A) Covalent B) Ionic C) Metallic D) Intermolecular

3. Which is the correct order of reactivity (most reactive first)? (1 mark) A) copper, iron, magnesium B) magnesium, iron, copper C) iron, copper, magnesium D) copper, magnesium, iron

4. A reaction that transfers energy to the surroundings, raising the temperature, is: (1 mark) A) endothermic B) exothermic C) reversible D) neutral

5. What is the relative formula mass (Mr) of CO₂? (Ar: C = 12, O = 16) (1 mark) A) 28 B) 44 C) 56 D) 16

Section B — Structured Questions (47 marks)

6. Atoms contain sub-atomic particles. (a) State the relative charge and relative mass of a proton, a neutron and an electron. (3 marks) (b) Define the term isotope. (2 marks) (c) Describe how the alpha particle scattering experiment changed the model of the atom. (3 marks)

7. The periodic table arranges the elements. (a) State what all elements in the same group have in common about their electronic structure. (1 mark) (b) Explain why the reactivity of Group 1 metals increases down the group. (3 marks) (c) Chlorine can displace bromine from potassium bromide solution. Explain why. (2 marks)

8. Sodium chloride is an ionic compound. (a) Describe how ions form when sodium reacts with chlorine. (2 marks) (b) Explain why sodium chloride has a high melting point. (2 marks) (c) Explain why sodium chloride conducts electricity when molten or dissolved, but not when solid. (2 marks)

9. This question is about quantitative chemistry. (a) State the law of conservation of mass. (1 mark) (b) Calculate the number of moles in 8.0 g of magnesium oxide, MgO. (Ar: Mg = 24, O = 16) (2 marks) (c) Explain why the mass appears to decrease when a metal carbonate is heated in an open container. (2 marks)

10. Acids react with several substances. (a) Complete: acid + metal carbonate → salt + ______ + ______. (2 marks) (b) Name the salt formed when sulfuric acid reacts with copper oxide. (1 mark) (c) Describe how you would make pure, dry crystals of copper sulfate from copper oxide and sulfuric acid. (4 marks)

11. Electrolysis is used to break down compounds. (a) Explain why aluminium is extracted by electrolysis rather than by reduction with carbon. (2 marks) (b) During the electrolysis of molten lead bromide, name the product formed at each electrode. (2 marks) (c) Give a reason why cryolite is used in the extraction of aluminium. (1 mark)

Section C — Extended Response

12. Compare the structures and bonding in diamond and graphite, and explain how these account for the differences in their properties. (6 marks)

Mark Scheme

Section A: 1. D (11+12); 2. B; 3. B; 4. B; 5. B. (5)

6 (a) proton +1, mass 1; neutron 0, mass 1; electron −1, mass very small/negligible (3). (b) atoms of the same element (same protons) (1) with different numbers of neutrons (1). (c) most particles passed through → mostly empty space (1); a few deflected → small dense nucleus (1); nucleus is positively charged (1). (8)

7 (a) same number of outer-shell electrons (1). (b) outer electron further from nucleus (1); more shielding (1); so lost more easily → more reactive (1). (c) chlorine is more reactive than bromine (1); so it displaces bromine from its salt (1). (6)

8 (a) sodium loses one electron → Na⁺ (1); chlorine gains one electron → Cl⁻ (1). (b) strong electrostatic forces between oppositely charged ions (1); need lots of energy to overcome (1). (c) when molten/dissolved the ions are free to move and carry charge (1); when solid the ions are fixed in place (1). (6)

9 (a) no atoms are created or destroyed; total mass of reactants = total mass of products (1). (b) Mr of MgO = 40; moles = 8.0 ÷ 40 = 0.2 mol (1 method, 1 answer). (c) carbon dioxide gas is given off and escapes (1); so the remaining mass is less (1). (5)

10 (a) water (1); carbon dioxide (1). (b) copper sulfate (1). (c) add excess copper oxide to warm sulfuric acid (1); filter off the excess solid (1); heat the solution to the point of crystallisation / evaporate some water (1); leave to crystallise and dry (1). (7)

11 (a) aluminium is more reactive than carbon (1); so carbon cannot reduce it / electrolysis needed (1). (b) cathode: lead (1); anode: bromine (1). (c) lowers the melting point (saving energy) (1). (5)

12 — Levels (6): Indicative: both are giant covalent structures of carbon with strong covalent bonds and high melting points. Diamond: each carbon bonded to 4 others → rigid 3D lattice → very hard; no free electrons → does not conduct. Graphite: each carbon bonded to 3 others → layers that can slide → soft/lubricant; one delocalised electron per atom → conducts electricity.

L3 (5–6): Both structures described and clearly linked to at least two property differences (hardness and conductivity).

L2 (3–4): Describes the structures with some links to properties.

L1 (1–2): Simple statements.

Sample Answers with Examiner Commentary

Question 12 — Sample Answers

Grade 9 answer "Diamond and graphite are both giant covalent structures made only of carbon, with strong covalent bonds, which is why both have very high melting points. In diamond, each carbon atom is covalently bonded to four others in a rigid 3D lattice, making it very hard and useful for cutting tools; it has no free electrons so it does not conduct electricity. In graphite, each carbon is bonded to only three others, forming layers held together by weak forces that can slide over each other, so graphite is soft and slippery and used as a lubricant. Each carbon also has one delocalised electron, so graphite conducts electricity, unlike diamond." Mark: 6/6. Examiner commentary: Both structures are described precisely (4 vs 3 bonds, layers, delocalised electrons) and clearly linked to hardness and conductivity. Top band.

Grade 6 answer "Diamond is very hard because each carbon is joined to four others. Graphite is soft because it has layers that slide. Graphite can conduct electricity but diamond can't." Mark: 4/6. Examiner commentary: Correct key points on bonding number, sliding layers and conductivity, but does not explain conductivity using delocalised electrons, and the high melting point/giant structure is not mentioned. Adding those would reach the top band.

Question 9(b) — Sample Answers

Grade 9 answer "The relative formula mass of MgO is 24 + 16 = 40. Moles = mass ÷ Mr = 8.0 ÷ 40 = 0.2 mol." Mark: 2/2. Examiner commentary: Correct Mr, correct method and answer with units.