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A chemical cell produces electricity through redox reactions between electrodes and an electrolyte. Free notes with key terms and 10 questions answered.
How Cells and Batteries Work is part of Chemical cells and fuel cells (chemistry only) in GCSE AQA Higher Chemistry.
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A chemical cell produces electricity through redox reactions between electrodes and an electrolyte. Free notes with key terms and 10 questions answered.
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Use this lesson to stay inside Chemical cells and fuel cells (chemistry only) while connecting the detail back to the wider Topic 5: Energy changes topic.
Read the core explanations from How Cells and Batteries Work before testing yourself from memory.
Your phone battery is dead. You plug it in, and electricity flows. But where does that electricity actually come from? It's not magic — it's chemistry in action.
Inside every battery and cell, chemicals are reacting to push electrons around a circuit. Think of it like a chemical pump that never stops working, as long as the chemicals last.
Picture two different metal strips dipped into a beaker of salt water. Connect them with a wire, and current flows. You've just made a simple cell.
Every simple cell needs three components working together. Remove any one of them, and the electricity stops.
Here's what happens: one metal gives up electrons more easily than the other. The 'generous' metal becomes the negative terminal, whilst the 'greedy' metal becomes positive. The electrolyte completes the circuit by allowing ions to move between the electrodes.
Not all cells produce the same voltage. A car battery gives 12V, whilst a watch battery gives 1.5V. The voltage depends on the specific materials you choose.
Three main factors control how much voltage a cell produces. Change any of these, and you change the voltage output.
Factor 1: Type of electrodesDifferent electrode materials can give different voltages. Magnesium and copper give more voltage than zinc and copper, because magnesium is much more reactive than zinc.
Factor 2: Type of electrolyteThe electrolyte helps the cell work.
Factor 3: Concentration of electrolyteThe cell voltage depends on the materials used.
One cell might give you 1.5V. But your laptop needs 12V to run. How do we get more voltage? We connect multiple cells together.
Cells can be joined together to make a battery with a higher voltage.
Worked example: Calculating Battery Voltage
A battery contains 8 identical cells, each producing 1.5V. Calculate the total voltage of the battery.
Answer: 12V
Important: Batteries can be designed in different ways depending on the voltage needed.
Understanding how cells work helps explain why different devices use different types of batteries. A hearing aid needs a tiny, long-lasting cell. A car needs a powerful battery that can deliver lots of current quickly.
Alkaline batteries use zinc and manganese dioxide electrodes with an alkaline electrolyte. They're cheap and reliable for everyday devices. Lithium batteries use lithium metal electrodes and give higher voltage — perfect for phones and laptops where space matters.
Car batteries are different again. They use lead electrodes in sulfuric acid and can be recharged hundreds of times. The chemical reactions are reversible — applying electricity forces the reactions backwards, storing energy for later use.
Exam questions on cells and batteries often test your understanding of what affects voltage and how to calculate total voltage in series circuits. Here's how to tackle them confidently.
Watch out for questions that mix up cause and effect. The voltage depends on the materials you choose, not on how much current flows. A cell produces the same voltage whether it's powering a small LED or sitting disconnected on the shelf.
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Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.
An electrode is a conductor through which electricity enters or leaves an electrolyte during chemical reactions. In a cell, one electrode loses electrons (anode) while the other gains electrons (cathode).
A car battery uses lead electrodes in sulfuric acid and can be recharged hundreds of times. Its chemical reactions are reversible, so applying electricity forces the reactions backwards, storing energy for later use.
The total voltage of a battery made of identical cells connected in series is the number of cells × the voltage of each cell. For example, 8 cells of 1.5V give a total voltage of 8 × 1.5V = 12V.
A chemical cell produces electricity through redox reactions between electrodes and an electrolyte: one metal gives up electrons more easily than the other and becomes the negative terminal. The reactions create a potential difference that drives current through an external circuit.
The voltage of a cell depends on the materials used: the type of electrodes, the type of electrolyte and the concentration of the electrolyte. For example, magnesium and copper give more voltage than zinc and copper, because magnesium is much more reactive than zinc.
A cell is a single device that converts chemical energy into electrical energy, while a battery is two or more cells combined to give a higher voltage. For example, one cell might give 1.5V, but a laptop needs 12V.
A simple cell is made of two different metal electrodes dipped into an electrolyte, such as salt water, and connected by a wire. The electrolyte contains free ions that complete the circuit by moving between the electrodes.
A magnesium and copper cell gives more voltage than a zinc and copper cell because magnesium is much more reactive than zinc. The type of electrodes is one of the main factors that controls the voltage a cell produces.
The metal that gives up electrons more easily, the more reactive one, becomes the negative terminal of a simple cell, while the other metal becomes positive. The electrolyte completes the circuit by allowing ions to move between the electrodes.
A cell's voltage depends on the materials chosen, not on how much current flows. A cell produces the same voltage whether it is powering a small LED or sitting disconnected on the shelf.