1. 1
   A student builds a simple chemical cell using two different metal electrodes placed in a beaker of electrolyte solution, and connects a voltmeter across the two electrodes, which reads a steady value. The student leaves the cell connected to a small bulb overnight.

   (a)

   A student connects a simple chemical cell, made from two different metal electrodes in an electrolyte solution, to a voltmeter, and reads a steady potential difference. What is producing this potential difference?

   [1 mark]

   • AChemical reactions occurring at the two electrodes
   • BThe voltmeter itself generating electricity
   • CHeat energy from the surroundings
   • DFriction between the electrodes and the solution

   (b)

   The next morning, the student finds that the bulb is no longer lit and the voltmeter reads close to zero. What is the most likely explanation?

   [1 mark]

   • AThe metal electrodes have become magnetised
   • BThe voltmeter has stopped working
   • CThe electrolyte solution has evaporated completely
   • DThe reactants in the cell have been used up

   (c)

   Explain why the potential difference produced by a chemical cell decreases and eventually stops as it is used, and suggest one way the student could restore the potential difference of this simple cell.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A torch manufacturer sells non-rechargeable batteries, each containing chemicals that react to produce a potential difference. Customers are advised to dispose of each battery responsibly once it stops working, rather than trying to reuse it.

   (a)

   A manufacturer produces non-rechargeable batteries for use in a torch. Once the chemicals inside a battery have been used up, what happens?

   [1 mark]

   • AThe battery continues to produce a potential difference indefinitely
   • BThe battery stops producing a useful potential difference and cannot be reused
   • CThe battery automatically refills its own chemicals
   • DThe battery's potential difference increases further

   (b)

   Why should used batteries be disposed of responsibly, according to the manufacturer's advice?

   [1 mark]

   • ABecause batteries become more reactive after use
   • BBecause used batteries can still produce a useful voltage if buried
   • CBecause the chemicals inside batteries can be hazardous to the environment if released
   • DBecause used batteries generate heat indefinitely

   (c)

   Explain, in terms of the chemical reactions inside, why a non-rechargeable battery cannot be reused once it has stopped producing a useful potential difference.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   An electronics hobbyist builds a simple chemical cell from a copper electrode and a zinc electrode placed in a beaker of dilute sulfuric acid, connecting a voltmeter across the two electrodes to measure the potential difference produced.

   (a)

   An electronics hobbyist builds a simple chemical cell using a copper electrode and a zinc electrode placed in dilute sulfuric acid, and measures a potential difference across the electrodes using a voltmeter. Explain the source of this potential difference and predict, giving a reason, what would happen to the reading over a long period of continuous use.

   [3 marks]

   (b)

   The hobbyist then builds a second cell using magnesium instead of zinc, keeping the copper electrode and acid the same, and finds a larger potential difference is produced. Suggest a reason for this difference, and describe an investigation the hobbyist could carry out to compare the potential difference produced by several different pairs of metal electrodes fairly.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A remote environmental research station uses simple chemical cells to power small weather sensors in locations where mains electricity is not available, and the maintenance team is planning how often the cells will need to be checked or replaced.

   (a)

   A remote research station relies on simple chemical cells to power small sensors when mains electricity is unavailable. Explain fully how a chemical cell produces a potential difference, why this potential difference cannot be maintained indefinitely, and discuss the practical implications of this for the research station's equipment.

   [6 marks]

   (b)

   Discuss why the research station might consider using hydrogen fuel cells instead of simple chemical cells for some of its sensors, in terms of how the potential difference is maintained and the practicality of long-term, remote operation.

   [6 marks]

   Total for question 4: 12 marks

End of questions