GCSE Chemistry: Chemical Cells, Batteries and Fuel Cells

Chemical cells turn the energy released by a chemical reaction directly into electricity. In separate GCSE Chemistry this is part of the energy changes topic, alongside exothermic and endothermic reactions and bond energies, which the category's energy changes material already covers. This material fills in the electrochemical part: simple cells, batteries, rechargeable and non-rechargeable cells, and the hydrogen fuel cell.

The quiz opens with simple cells made from two different metals in an electrolyte. You use the reactivity series to decide which pair of metals gives the largest voltage, and predict the voltage of a new pair from results measured against copper — the bigger the difference in reactivity, the bigger the voltage, and two electrodes of the same metal give none. You then add the voltages of cells joined in series to make a battery, explain why a non-rechargeable alkaline battery eventually stops (one reactant is used up) and why a rechargeable cell can be used again (an external current reverses the reactions).

The second half is about fuel cells. A fuel cell is supplied continuously with a fuel, such as hydrogen, and with oxygen or air; the fuel is oxidised electrochemically to produce a potential difference, and the overall reaction of a hydrogen fuel cell, 2H₂ + O₂ → 2H₂O, leaves water as the only product. Two Higher-tier questions ask which half equation happens at which electrode in a cell with an acidic electrolyte, and whether it is oxidation or reduction. The set ends with the comparison that is often asked as an extended-writing question: the advantages of hydrogen fuel cells over rechargeable batteries, and their disadvantages, from storing a flammable gas to the way the hydrogen is produced.

The flashcards hold the key definitions and equations. In the oral exam an examiner asks one question at a time — how a simple cell works, why a battery goes flat, what happens at each electrode of a fuel cell — and gives brief, precise feedback at the end. The printable written work has eight longer tasks answered by hand, including interpreting cell voltage data, writing and explaining the half equations, and a balanced evaluation of hydrogen fuel cells against rechargeable batteries for powering a car, each checked against a model answer.

The content is based on the energy changes section of the DfE GCSE chemistry subject content; for example, the AQA specification places chemical cells and fuel cells in its chemistry-only content, with the fuel cell half equations for Higher tier only.

• Explain how a simple cell is made and how the choice of metals affects its voltage
• Use voltage data and the reactivity series to predict the voltage of a cell
• Explain what a battery is and calculate the voltage of cells in series
• Explain why non-rechargeable cells stop working and why rechargeable cells can be recharged
• Describe how a hydrogen fuel cell produces electricity and write its overall equation
• Write the half equations at each electrode of a hydrogen fuel cell and identify oxidation and reduction (Higher tier)
• Evaluate the use of hydrogen fuel cells compared with rechargeable batteries

Practice material written by Zestly, based on the DfE GCSE chemistry subject content (energy changes: chemical cells and fuel cells); chemistry-only and Higher-tier placement given as an example from the AQA GCSE Chemistry (8462) specification. Cell voltages in the questions are illustrative values.