AQA GCSE Combined Science: Synergy — Paper 3 (Physical Sciences, Higher Tier)

Total marks: 100 · Duration: 105 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 assesses Topics 4.5–4.8: Building blocks for understanding; Interactions over small and large distances; Movement and interactions; and Guiding Spaceship Earth.
The maximum mark for this paper is 100. The marks for each question are shown in brackets.

Paper

Section A — Multiple Choice (6 marks)

1. Elements in the same group of the periodic table have the same number of: (1 mark) A) protons B) neutrons C) outer-shell electrons D) shells

2. Which type of bonding holds metals together? (1 mark) A) Ionic B) Covalent C) Metallic D) Intermolecular

3. The unit of force is the: (1 mark) A) joule B) newton C) watt D) pascal

4. Like magnetic poles: (1 mark) A) attract B) repel C) cancel out D) become neutral

5. Cracking is used to turn long-chain hydrocarbons into: (1 mark) A) crude oil B) smaller, more useful molecules C) metals D) salts

6. Which energy resource is renewable? (1 mark) A) Coal B) Natural gas C) Wind D) Nuclear

Section B — Structured Questions (60 marks)

7. The periodic table organises elements. (4.5.1) (a) Explain why Group 0 elements (noble gases) are unreactive. (2 marks) (b) Describe the trend in reactivity down Group 1 and explain it. (3 marks) (c) State the trend in melting points down Group 7. (1 mark)

8. Chemical amounts can be calculated. (4.5.2) (a) State the law of conservation of mass. (1 mark) (b) Calculate the relative formula mass of calcium carbonate, CaCO₃. (Ar: Ca = 40, C = 12, O = 16) (2 marks) (c) Calculate the concentration in g/dm³ when 15 g of solute is dissolved in 250 cm³ of solution. (2 marks)

9. Substances have different structures and bonding. (4.6.2) (a) Describe how ions form in an ionic compound. (2 marks) (b) Explain why ionic compounds conduct electricity only when molten or dissolved. (2 marks) (c) Explain why simple molecular substances have low melting points. (2 marks)

10. Forces affect motion. (4.6.1 / 4.7.1) (a) Calculate the work done when a force of 30 N moves an object 4 m. (2 marks) (b) State Newton's First Law of motion. (1 mark) (c) Calculate the acceleration of a 2 kg mass acted on by a resultant force of 10 N. (2 marks)

11. Electricity is used in circuits. (4.7.2) (a) State the equation linking charge, current and time. (1 mark) (b) Calculate the resistance of a component with a current of 2 A and potential difference of 12 V. (2 marks) (c) Describe how the current and potential difference behave in a series circuit. (2 marks)

12. Magnetism and electromagnetism. (4.6.3) (a) Describe the magnetic field around a bar magnet. (2 marks) (b) Explain how to increase the strength of an electromagnet. (2 marks)

13. Resources must be used sustainably. (4.8.2) (a) Explain the difference between a finite and a renewable resource, with an example of each. (2 marks) (b) Calculate the efficiency of a motor that transfers 80 J usefully from 200 J of input energy. (2 marks) (c) Describe one way to reduce unwanted energy transfers in a device. (1 mark)

Section C — Extended Response

14. Crude oil is separated and processed to make useful products. Describe how fractional distillation separates crude oil, and explain why cracking is used on some of the fractions. (6 marks)

Mark Scheme

Section A: 1. C; 2. C; 3. B; 4. B; 5. B; 6. C. (6)

7 (a) full outer shell of electrons (1); so do not easily gain/lose/share electrons (1). (b) reactivity increases down the group (1); outer electron further from nucleus / more shielding (1); lost more easily (1). (c) melting points increase down the group (1). (6)

8 (a) total mass of reactants = total mass of products (1). (b) 40 + 12 + (3×16) = 100 (1 method, 1 answer). (c) 250 cm³ = 0.25 dm³; 15 ÷ 0.25 = 60 g/dm³ (1 method, 1 answer). (5)

9 (a) metal atom loses electrons → positive ion (1); non-metal gains electrons → negative ion (1). (b) ions are free to move when molten/dissolved (1); fixed when solid (1). (c) weak intermolecular forces between molecules (1); little energy needed to overcome them (1). (6)

10 (a) W = Fd = 30 × 4 = 120 J (1 method, 1 answer). (b) an object stays at rest or moves at constant velocity unless acted on by a resultant force (1). (c) a = F ÷ m = 10 ÷ 2 = 5 m/s² (1 method, 1 answer). (5)

11 (a) Q = I × t (1). (b) R = V ÷ I = 12 ÷ 2 = 6 Ω (1 method, 1 answer). (c) current is the same everywhere (1); potential difference is shared between components (1). (5)

12 (a) field lines from north to south (1); strongest at the poles (1). (b) any two: more current; more turns; iron core (2). (4)

13 (a) finite runs out (e.g. fossil fuels) (1); renewable is replaced as used (e.g. wind/timber) (1). (b) efficiency = 80 ÷ 200 = 0.4 = 40% (1 method, 1 answer). (c) lubrication to reduce friction / insulation to reduce heat loss (1). (5)

14 — Levels (6): Indicative: crude oil is heated and evaporates; vapours rise up a fractionating column that is hot at the bottom, cooler at the top; each fraction condenses at its boiling point (larger molecules lower down). Cracking breaks long-chain (less useful, low demand) molecules into smaller, more useful ones (fuels) and alkenes (for polymers), matching supply to demand.

L3 (5–6): Correct description of fractional distillation and the reason for cracking.

L2 (3–4): Some of each.

L1 (1–2): Simple statements.

Sample Answers with Examiner Commentary

Question 14 — Sample Answers

Grade 9 answer "In fractional distillation, the crude oil is heated until it evaporates and the vapours pass into a fractionating column that is hot at the bottom and cooler towards the top. As the vapours rise and cool, each fraction condenses at the height where the temperature matches its boiling point — fractions with larger molecules and higher boiling points condense lower down, and smaller molecules condense near the top. Cracking is then used on some of the longer-chain fractions because they are less useful and in lower demand. Cracking breaks them into smaller, more useful molecules such as petrol, and also produces alkenes which are used to make polymers. This matches the supply of products to what people actually want." Mark: 6/6. Examiner commentary: Accurate, ordered account of fractional distillation linked to boiling point, plus a clear reason for cracking (demand) and its useful products. Top band.

Grade 6 answer "Crude oil is heated and the different parts boil off at different temperatures and are collected. Cracking breaks big molecules into smaller ones that are more useful as fuels." Mark: 4/6. Examiner commentary: The basic idea of separation by boiling point and the purpose of cracking are correct, but the column temperature gradient (hot bottom, cool top) and alkenes/demand are missing, which would reach the top band.

Question 8(b) — Sample Answers

Grade 9 answer "Mr of CaCO₃ = 40 + 12 + (3 × 16) = 40 + 12 + 48 = 100." Mark: 2/2. Examiner commentary: Correct working including the three oxygen atoms, correct answer.