OCR GCSE Chemistry A: Improving processes and products (J248)

Sub-topic C6.1 Improving processes and products opens Topic C6 Global challenges in OCR’s Chemistry A (Gateway Science) specification for GCSE (9–1), code J248, in its Version 4.0 issue of August 2026. This guide teaches every learning outcome from C6.1a to C6.1s, the mathematical learning outcomes CM6.1i to CM6.1iv, and the practical suggestions linked to PAG C1, PAG C2 and PAG C6. Outcomes C6.1c, C6.1d, C6.1e and C6.1f are Higher Tier only; the other statements can appear on either tier. The assessment overview places Topic C6 on Paper 2 (Foundation) and Paper 4 (Higher), and both papers include synoptic assessment.

Other J248 topics sit on the course hub for OCR GCSE Chemistry; a statement-by-statement J248 checklist is free to print. To find your weakest areas quickly, try a free 10-minute chemistry diagnostic.

Statements in C6.1

Statement	Skill required	Tier
C6.1a	Explain carbon extraction of metals using carbon’s place in the reactivity series, including a non-ferrous metal	Both tiers
C6.1b	Explain why and how electrolysis extracts some metals	Both tiers
C6.1c	Evaluate bacterial extraction and phytoextraction	Higher Tier only
C6.1d	Explain the trade-off between rate and equilibrium position (Haber, Contact)	Higher Tier only
C6.1e	Interpret graphs of reaction conditions against rate	Higher Tier only
C6.1f	Link commercial conditions to raw materials, energy, equilibrium and rate	Higher Tier only
C6.1g	Explain why the Haber process matters to agriculture	Both tiers
C6.1h–j	Fertilisers: N, P and K; industrial versus laboratory production; integrated processes	Both tiers
C6.1k–l	Carry out and interpret a life-cycle assessment	Both tiers
C6.1m–n	Recycling for a different use; factors in recycling decisions	Both tiers
C6.1o–q	Alloys; corrosion; barrier and sacrificial protection	Both tiers
C6.1r–s	Compare glass, clay ceramics, polymers, composites and metals; choose materials	Both tiers
CM6.1i–iv	Rate arithmetic, rate graphs, gradients, proportionality	Both tiers

Extracting metals with carbon (C6.1a)

Most metals occur in ores as compounds, often oxides. Extraction is reduction: removing the oxygen. Carbon sits between aluminium and zinc in the reactivity series, so:

• metals less reactive than carbon (zinc, iron, tin, lead, copper) can be reduced by heating the oxide with carbon;
• metals more reactive than carbon (aluminium, magnesium, sodium) cannot.

In the blast furnace, carbon monoxide from coke reduces iron(III) oxide: Fe₂O₃ + 3CO → 2Fe + 3CO₂. Copper is a non-ferrous example: 2CuO + C → 2Cu + CO₂.

PAG C1 practical. Heat copper(II) oxide with excess carbon powder in a covered crucible. Brown-pink specks of copper form in the black powder.

Worked example. A student heats 4.00 g of copper(II) oxide with carbon and recovers 2.72 g of copper. Find the percentage yield. Relative atomic masses: Cu = 63.5, O = 16.

1. Mr of CuO = 63.5 + 16 = 79.5.
2. Fraction of the mass that is copper = 63.5 ÷ 79.5. Maximum copper = 4.00 × 63.5 ÷ 79.5 = 3.19 g.
3. Percentage yield = 2.72 ÷ 3.19 × 100 = 85.1% (using the unrounded 3.195).

Extracting metals by electrolysis (C6.1b)

Why: carbon cannot reduce the oxides of metals above it, so electrical energy forces the reduction. It costs more than carbon reduction: large currents run for long periods and the ore must be molten.

How (aluminium): aluminium oxide is dissolved in molten cryolite, which lowers the operating temperature and saves energy. The ions must be free to move.

• Cathode (negative): Al³⁺ + 3e⁻ → Al. Molten aluminium collects at the bottom.
• Anode (positive): 2O²⁻ → O₂ + 4e⁻. The oxygen reacts with the hot carbon anodes to make carbon dioxide, so the anodes wear away and are replaced.

PAG C2 practicals. With inert electrodes:

Solution	Cathode product	Anode product	Test
Aqueous sodium chloride	hydrogen	chlorine	squeaky pop; damp blue litmus turns red then bleaches
Aqueous copper sulfate	copper	oxygen	pink-brown coating; relights a glowing splint

Graph skill (M4b, M4c). A student weighs the cathode during copper sulfate electrolysis:

Time / min	0	4	8	12	16
Mass gained / g	0	0.10	0.19	0.30	0.40

Plot time on the x-axis and draw a line of best fit through the origin. Gradient = 0.40 ÷ 16 = 0.025 g/min, the rate at which copper is deposited.

Biological extraction (C6.1c, Higher Tier only)

High-grade copper ores are running out. Two biological methods work on low-grade ore.

• Bacterial extraction (bioleaching): bacteria break down compounds in low-grade ore and produce a solution (leachate) containing copper ions. Copper is then obtained by displacement with scrap iron or by electrolysis.
• Phytoextraction: plants grown on the ore absorb metal ions. The crop is cut and burned, leaving ash rich in metal compounds.

For	Against
Uses ore too poor to mine conventionally	Very slow (months or years)
No large open-cast mine, less waste rock	Leachate can be toxic if it escapes
Lower energy use than smelting	Burning plants releases carbon dioxide

An “evaluate” answer weighs both sides and ends with a judgement.

Rate against equilibrium (C6.1d, C6.1e, C6.1f; Higher Tier only)

Haber process: N₂ + 3H₂ ⇌ 2NH₃, forward reaction exothermic. Conditions: about 450 °C, about 200 atmospheres, iron catalyst.

• A lower temperature would give a higher yield but too slow a rate, so 450 °C is a compromise.
• Four gas molecules become two, so high pressure shifts equilibrium right and raises the rate. Higher pressures need costly compression and stronger plant.
• The iron catalyst increases rate but not yield.
• Unreacted nitrogen and hydrogen are recycled, so little is wasted.

Contact process: 2SO₂ + O₂ ⇌ 2SO₃, forward reaction exothermic. Conditions: about 450 °C, pressure close to atmospheric, vanadium(V) oxide catalyst. The equilibrium already lies far to the right, so extra pressure would add cost for little gain.

Commercial conditions (C6.1f) balance the cost and availability of raw materials (air, natural gas, sulfur), energy costs for heating and compression, equilibrium yield and rate. A fast reaction with a modest yield plus recycling can beat a slow one with a high yield.

Rate graphs (C6.1e, CM6.1i–iv). On a product-against-time curve, the rate at any moment is the gradient of the tangent.

Worked example. A tangent to a volume-of-gas curve passes through (0 s, 8 cm³) and (40 s, 56 cm³). Rate = (56 − 8) ÷ (40 − 0) = 1.2 cm³/s. In another run, doubling the concentration from 0.40 to 0.80 mol/dm³ doubles the initial rate from 0.021 to 0.042 cm³/s, so rate is directly proportional to concentration: a straight line through the origin on a rate–concentration graph.

The Haber process and agriculture (C6.1g)

Ammonia from the Haber process is the starting point for most nitrogen fertilisers. Plants need nitrogen to make proteins, so fertilisers raise crop yields and let farms feed far more people than natural nitrogen sources could.

Fertilisers (C6.1h, C6.1i, C6.1j)

N, P and K: compounds of these replace elements that crops remove from soil. They must be soluble so roots can absorb them.

Integrated industrial production (C6.1j). Several plants feed each other on one site:

• Air and natural gas → hydrogen and nitrogen → ammonia (Haber).
• Ammonia oxidised → nitric acid; ammonia + nitric acid → ammonium nitrate.
• Sulfur → sulfuric acid (Contact); ammonia + sulfuric acid → ammonium sulfate.
• Phosphate rock and mined potassium chloride supply P and K.

Worked example. Potassium sulfate, K₂SO₄, supplies potassium. Using K = 39, S = 32, O = 16: Mr = 78 + 32 + 64 = 174. Percentage of potassium = 78 ÷ 174 × 100 = 44.8%.

Laboratory synthesis (C6.1h, PAG C6). Titrate ammonia solution with dilute sulfuric acid using an indicator to find the volume needed. Repeat with the same volumes and no indicator, then evaporate some water and leave to crystallise. Potassium sulfate can be made the same way from potassium hydroxide solution.

Laboratory	Industry
Batch process, grams	Continuous process, tonnes
Dilute solutions bought in	Concentrated reactants made on site
Heating to evaporate water	Heat from the exothermic reaction is reused
Several steps by hand	Automated, few workers per tonne

Life-cycle assessment (C6.1k, C6.1l)

A life-cycle assessment (LCA) totals the resources used and the environmental impact at every stage:

1. making the materials from raw materials, and the process that makes the product;
2. the use of the product;
3. transport of the product;
4. disposal at the end of its life.

Energy use can be measured; some effects, such as landscape damage, need value judgements.

Worked example. Use these illustrative values. A steel drinks bottle takes 18 MJ to make and transport and 0.05 MJ to wash per use. A single-use plastic bottle takes 1.2 MJ each. After how many uses is the steel bottle better?

Steel total = 18 + 0.05n; plastic total = 1.2n. They are equal when 18 = 1.15n, n = 15.7, so from the 16th use steel uses less energy (18.8 MJ against 19.2 MJ).

Recycling (C6.1m, C6.1n)

Plastic drinks bottles are washed, shredded, melted and drawn into fibres for fleece clothing. Waste glass of the wrong colour for new bottles is crushed into aggregate for road surfaces. Both are viable because the material is collected in bulk, the new use does not need high purity, and new raw materials and landfill space are saved.

Factors in recycling decisions: cost and energy of collection, transport and sorting; how easily materials separate; value of recycled against new material; scarcity of the raw material; energy saved; landfill charges.

Alloys, corrosion and protection (C6.1o, C6.1p, C6.1q)

Alloy	Main metals	Property	Use
Steel	iron with carbon (stainless also chromium, nickel)	strong; stainless resists corrosion	bridges, cutlery
Brass	copper and zinc	hard, does not rust, easy to machine	door handles, musical instruments
Bronze	copper and tin	hard, resists corrosion	statues, ship propellers
Solder	tin with lead, or tin with small amounts of copper or silver	low melting point	joining electrical components
Duralumin	aluminium with about 4% copper and small amounts of magnesium and manganese	strong, low density	aircraft parts

Corrosion is a metal reacting with substances around it. Iron rusts only when both oxygen and water are present, forming hydrated iron(III) oxide, which flakes off and exposes more metal. Salt speeds rusting. Aluminium’s thin oxide layer protects it; copper slowly turns green.

Mitigation: a physical barrier (paint, oil, grease, plastic coating, plating) keeps oxygen and water off. Sacrificial protection attaches a more reactive metal, such as zinc or magnesium, which oxidises instead of the iron. Galvanising (a zinc coating) is both, so it still protects when scratched.

Choosing materials (C6.1r, C6.1s)

Illustrative values for comparison:

Material	Density / g/cm³	Tensile strength / MPa	Notes
Glass	2.5	50	transparent, brittle
Clay ceramic	2.0	5	hard, brittle, high melting point
Poly(ethene)	0.95	25	flexible, electrical insulator
Carbon-fibre composite	1.6	600	strong, light, costly
Steel	7.8	400	strong, tough, conducts
Aluminium alloy	2.8	300	light, resists corrosion

To compare quantitatively, divide strength by density: composite 375, aluminium alloy 107, steel 51. The composite suits a racing-bike frame; steel’s toughness and low cost suit a bridge.

Common errors

• Saying carbon extracts aluminium. Aluminium is above carbon.
• Calling cryolite a catalyst.
• Claiming a catalyst increases the yield of ammonia.
• Giving only one condition for rusting.
• Not saying the sacrificial metal is more reactive.
• Missing an LCA stage, often transport or disposal.

Next steps

For a condensed version, open the C6.1 revision notes; for exam-style questions, open the C6.1 practice set. Background: formulae and equations (C3.1 guide), relative formula mass (C2.1 guide) and bulk properties (C2.3 guide).

Official syllabus

Source document, published by OCR: the GCSE (9–1) Chemistry A (Gateway Science) specification, code J248, Version 4.0, August 2026, with first assessment in 2018. Used here: sub-topic C6.1 Improving processes and products, with statements C6.1a–C6.1s, maths outcomes CM6.1i–CM6.1iv and the PAG C1, PAG C2 and PAG C6 practical suggestions.