AQA GCSE Chemistry Chemistry Paper 1 (Foundation), November 2021: Question 2

✅ Correct Answers

• Zinc-carbon: Cheapest / lowest purchase cost (£0.17).
• Alkaline: Longest lasting / lasts the most months before replacement (12 months).
• Nickel-metal hydride: Rechargeable / does not need to be thrown away when flat.

🧠 Exam Technique

Always state comparatives or superlatives (e.g. cheapest, longest lasting) rather than vague absolute terms.

• Saying "Zinc-carbon is cheap" is acceptable, but "cheapest" is stronger.
• Do not copy just raw numbers without context; explain the advantage clearly.

❌ Common Errors

• Confusing the batteries: Writing that alkaline batteries are rechargeable (the table states "No").
• Vague statements: Writing "it works well" or "it is good value" without stating why (cost, lifetime, or rechargeability).

✅ Correct Answers (Any one)

• Toxic / harmful / corrosive chemicals (or heavy metals/alkalis) could leak out.
• Could cause pollution / contamination in landfill sites (leaching into groundwater).
• Recycling batteries conserves finite metal resources.
• Batteries could ignite / catch fire / explode when crushed in waste disposal trucks or landfill.

❌ Common Errors

• Too vague: Just writing "they are dangerous" or "they are bad for the environment" scores 0 marks.
• You must state why they are dangerous (e.g. toxic chemicals leak, risk of fire) or how the environment is harmed (toxic metals in groundwater).

✅ Correct Answer

[X] Copper and iron

💡 Key Knowledge

In a simple chemical cell, the voltage produced depends on the difference in reactivity between the two metals:

• The greater the difference in reactivity, the higher the voltage.
• Iron is at the top (most reactive) and Copper is at the bottom (least reactive). Their gap is larger than Iron–Tin or Tin–Copper.

✅ Correct Answers (Any one)

• Concentration of the electrolyte solution.
• Temperature of the electrolyte solution.
• Distance between the electrodes.
• Surface area / size / mass / length of the electrodes.
• Volume of the electrolyte solution.

❌ Common Errors

• Repeating information from the question stem: The question already says voltage depends on "the type of electrodes and the type of electrolyte". Repeating "type of metal" or "type of liquid" is ignored and earns 0 marks.
• Focus on conditions like concentration or temperature.

✅ Correct Answer

hydrogen + oxygen → water

💡 Key Knowledge

• A hydrogen fuel cell combines hydrogen fuel and oxygen from the air.
• Overall reaction: 2H₂ + O₂ → 2H₂O
• The only product is pure water, making hydrogen fuel cells clean at point of use with zero carbon emissions.

❌ Common Errors

• Writing "air" instead of oxygen (air contains oxygen, but the reacting chemical element is oxygen).
• Writing "hydroxide" or "oxide" instead of oxygen.
• Writing chemical formulas with incorrect casing or missing subscripts, e.g. h2 or H2 without proper subscript notation. However, word answers avoid this risk entirely!