AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Fuel cells are supplied by an external source of fuel (eg hydrogen) and…
Full specification wording
Fuel cells: Fuel cells are supplied by an external source of fuel (eg hydrogen) and oxygen or air.
A fuel cell is a device that generates a potential difference continuously as long as it is supplied with fuel and oxygen.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 1 of 5
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A fuel cell is a device that generates a potential difference continuously as long as it is supplied with fuel and oxygen. Unlike a battery, which stores a fixed amount of chemical energy, a fuel cell is fed from outside. In a hydrogen fuel cell, hydrogen is supplied from a cylinder or store and oxygen is supplied from the air. The hydrogen is oxidised at one electrode and oxygen is reduced at the other, so the cell keeps working while both inputs continue. For example, in a hydrogen-powered vehicle, hydrogen from a tank and oxygen from the air enter the fuel cell, which produces electricity to drive the motor. This statement establishes that the reactants are external, not stored inside the cell.
What earns the marks
- A fuel cell requires a continuous external supply of fuel.
- Hydrogen is a common fuel used in fuel cells.
- Oxygen or air is supplied as the other reactant.
- The fuel and oxygen are fed into the cell from outside rather than being stored as the cell's only energy source.
- The cell produces a potential difference while the fuel and oxygen supplies continue.
Common mistakes and how to put them right
Treating a fuel cell as a battery that stores all its reactants internally.
Put it right by stating that fuel and oxygen are supplied continuously from external sources.
Naming only hydrogen as the input and forgetting oxygen or air.
Put it right by stating that both a fuel and oxygen or air are supplied.
Thinking the fuel cell must be recharged like a secondary cell.
Put it right by explaining that it operates as long as fuel and oxygen are supplied.
Exam tips
- In explanations, name both inputs: the fuel, such as hydrogen, and oxygen or air.
- Use the phrase external supply to make clear that the reactants are fed in continuously.
- Contrast a fuel cell with a battery by stating that a battery stores reactants while a fuel cell is supplied from outside.
Try the lesson
The start of the Fuel cells: Fuel cells are supplied by an external source of fuel (eg hydrogen) and oxygen or air. lesson, made from checked teaching notes for this specification point.
Have a go first
A hydrogen fuel cell is used to generate electricity. Which statement correctly describes how the reactants are supplied to the cell?
Listen
A fuel cell is a device that generates a potential difference continuously as long as it is supplied with fuel and oxygen. Unlike a battery, which stores a fixed amount of chemical energy, a fuel cell is fed from outside. In a hydrogen fuel cell, hydrogen is supplied from a cylinder or store and oxygen is supplied from the air. The hydrogen is oxidised at one electrode and oxygen is reduced at the other, so the cell keeps working while both inputs continue. For example, in a hydrogen-powered vehicle, hydrogen from a tank and oxygen from the air enter the fuel cell, which produces electricity to drive the motor. This statement establishes that the reactants are external, not stored inside the cell. A strong answer earns marks for these points. A fuel cell requires a continuous external supply of fuel. Hydrogen is a common fuel used in fuel cells. Oxygen or air is supplied as the other reactant. The fuel and oxygen are fed into the cell from outside rather than being stored as the cell's only energy source. A common slip: Treating a fuel cell as a battery that stores all its reactants internally. Instead, stating that fuel and oxygen are supplied continuously from external sources. Exam tip: In explanations, name both inputs: the fuel, such as hydrogen, and oxygen or air.
See it
Key words
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Fuel cells
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External reactants
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Hydrogen as a fuel
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Continuous electricity generation
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See every definition
- Fuel cells
- Devices supplied by an external source of fuel and oxygen or air, generating a potential difference continuously as long as they are supplied.
- External reactants
- The fuel and oxygen or air are fed into the cell from outside rather than being stored as the cell's only energy source.
- Hydrogen as a fuel
- A common fuel used in fuel cells, supplied from a cylinder or store, and oxidised at one electrode.
- Continuous electricity generation
- The cell produces a potential difference while the fuel and oxygen supplies continue, unlike a battery that stores a fixed amount of chemical energy.
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