AQA GCSE Chemistry Chemistry Paper 2 (Foundation), June 2025: Question 10

💡 Key Comparative Points from Table 5

• Raw Material: Aluminium ore (bauxite) is finite and mining/quarrying causes habitat loss and dust/noise pollution. Wood comes from trees, which are renewable, but growing trees requires vast land that could cause deforestation or reduce food farming space.
• Cost: Wood is significantly cheaper (relative cost 1 vs 87), meaning far more doors can be made for the same budget.
• Strength: Aluminium is stronger (1.3 vs 1.0), meaning it resists physical damage better and can have thinner frames.
• Maintenance: Aluminium naturally forms an oxide layer needing no protective painting, whereas wood must be painted to prevent rotting, adding labour and cost.
• Disposal: Both are sustainable at end-of-life—aluminium melts into new items (conserving metal ore); wood chips burn as a fuel alternative to fossil fuels.

✅ Model Answer Structure (Level 3: 5–6 Marks)

Pros and Cons of Wood: Wood is a renewable resource and 87 times cheaper than aluminium per kilogram. However, it is weaker (1.0 vs 1.3), requires periodic painting to stop it rotting, and using land for forestry reduces land for agriculture.

Pros and Cons of Aluminium: Aluminium is stronger and does not require maintenance painting because of its corrosion resistance. However, it is far more expensive (cost 87) and metal ore is a finite resource whose extraction causes landscape damage.

Disposal: Both materials are useful after disposal; aluminium can be melted down and recycled, while wood can be burned as biomass fuel.

Judgement: Overall, wood is better for standard household doors because it is vastly cheaper and renewable, provided regular painting is maintained.

🧠 Exam Technique: Securing Level 3 (5–6 Marks)

• Rule of thumb: Always discuss both materials, covering at least 3–4 categories from the table (Raw materials, Cost, Strength, Protection, Disposal).
• Give an explicit judgement: To reach Level 3, you must end with a justified conclusion stating which material you recommend and why. You can choose either, provided your argument backs it up!
• Explain the data: Don't just quote numbers. Say: "Aluminium has a relative cost of 87 compared to 1, meaning it is substantially more expensive."

❌ Common Mistakes to Avoid

• Pure data copying: Merely rewriting Table 5 without explaining the consequence (e.g. not explaining that "trees" = renewable or "mining" = habitat destruction) caps you at Level 1 (1–2 marks).
• Forgetting the conclusion: Leaving out a final decision automatically restricts your response to Level 2 maximum (4 marks).
• One-sided argument: Only discussing aluminium or only wood.

✅ Mark Scheme Breakdown

Mark 1: The oxide layer acts as a physical barrier.

Mark 2: It prevents air / oxygen / water from reaching the underlying aluminium / metal.

💡 Key Chemistry Concept

Aluminium is very reactive, but unlike iron, it reacts rapidly with atmospheric oxygen to form a thin, tough, tightly adhering layer of aluminium oxide (Al₂O₃):

4Al + 3O₂ → 2Al₂O₃

Because this layer does not flake off (unlike iron rust), it completely shields the underlying metal.

❌ Examiner Pitfalls & Prohibited Words

• Do NOT say "sacrificial protection": Aluminium oxide is NOT a sacrificial metal (like zinc on iron). It is a passive barrier!
• Do NOT say "prevents rusting": In GCSE Chemistry, rusting only applies to iron/steel. For aluminium, use the word corrosion.
• Do NOT just state: "It stops it reacting" without specifying what is blocked (must name air/oxygen or water).

✅ Correct Box to Tick

☑ A fixed mass of pigment and a fixed mass of liquid

All other three options list "variable mass", which is incorrect for a formulation.

💡 Definition of a Formulation

A formulation is a complex mixture designed as a useful product.

Every single component is carefully measured in fixed, specific quantities to ensure the product has the exact required properties (e.g. colour, drying speed, spreadability).

Other classic examples include medicines, fertilisers, cleaning agents, and fuels.

🧠 Quick Memory Tip

Remember the golden rule: Formulations = Fixed formulas!

If the masses were variable, every tin of paint would be a different shade, dry at a different speed, or fail to stick to the door.