Evaluate the use of hydrogen fuel cells compared to alkaline batteries as sources of electrical energy in portable devices.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Fuel cells can be supplied continuously with hydrogen from an external source, so they do not run out of energy as long as fuel is available, whereas alkaline batteries are non‑rechargeable and the chemical reaction stops when the reactants are exhausted.
Fuel cells produce only water as a by‑product, giving them a lower environmental impact than alkaline batteries, which generate waste products that must be disposed of.
A disadvantage of hydrogen fuel cells is that hydrogen must be stored separately, which is difficult, potentially dangerous and therefore less convenient for portable devices compared with the readily available alkaline batteries.
Fuel cells produce only water as a by‑product, giving them a lower environmental impact than alkaline batteries, which generate waste products that must be disposed of.
A disadvantage of hydrogen fuel cells is that hydrogen must be stored separately, which is difficult, potentially dangerous and therefore less convenient for portable devices compared with the readily available alkaline batteries.
Examiner tips
- Use the word ‘evaluate’ to compare both advantages and disadvantages; include all four scheme points.
- Show the continuous fuel supply and the single‑use nature of alkaline batteries. Mention the clean by‑product and the storage issue for hydrogen.
- Keep sentences concise and use exam terminology such as ‘non‑rechargeable’ and ‘by‑product’.
- Use bullet points or short sentences to cover each point clearly.
Common mistakes
- Failing to mention that alkaline batteries are non‑rechargeable. Not stating that fuel cells produce only water. Omitting the storage difficulty of hydrogen or the convenience of alkaline batteries.
Mark scheme (4 marks)
- Fuel cells are supplied continuously with fuel (hydrogen) from an external source, so they do not run out / stop working as long as fuel is supplied
- Alkaline batteries are non-rechargeable / the chemical reactions stop when one of the reactants has been used up
- Fuel cells produce only water as a by-product / do not produce polluting waste products, making them more environmentally friendly than alkaline batteries
- A disadvantage of hydrogen fuel cells is that hydrogen fuel must be stored / hydrogen is difficult or potentially dangerous to store, or alkaline batteries are more convenient / readily available for portable devices
Key terms in this question
fuel cells · alkaline batteries
Related
- All AQA GCSE Chemistry (8462) revision notes →
- How to answer a "Evaluate" question →
- Decode the mark scheme abbreviations →
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