Chemistry » Essential Ideas in Chemistry » Atoms And Compounds

Electrolysis of Water Experiment

Electrolysis of water is the decomposition of water into oxygen and hydrogen gas due to an electric current being passed through the water. The reaction has a standard potential of −1.23 V, meaning it ideally requires a potential difference of 1.23 volts to split water.

Experiment: The Electrolysis of Water


To investigate the elements that make up water.


  • water

  • two pencils sharpened at both ends

  • 9 volt battery

  • connecting wire

  • tape

  • table salt or sodium sulfate



Set up the apparatus as shown above. Observe what happens.


You should observe bubbles forming at the tips of the pencils. Oxygen gas is formed at the positive side and hydrogen at the negative side.

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