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Electrochemistry is the study of chemical properties and reactions that involve charged species (ions) in solution, and includes both electrolysis and electrochemical cells.
Electrolysis is the production of a chemical reaction, by passing a current through an electrolyte (a liquid that conducts electrons due to the presence of dissolved ions). In electrolysis you INPUT electricity, to PRODUCE a reaction. The positive ions migrate toward the cathode (negatively charged) and the negative ions migrate towards the anode (positively charged); electrons flow from anode to cathode around the circuit. At the cathode, positive ions in solution gain electrons to form new species via reduction, and at the anode, negative ions lose electrons to form oxidation products. Electrolysis is used in electroplating, e.g. for silver-plating jewellery. An example of this process can be seen in the image below whereby CuSO4 (copper sulfate) undergoes electrolysis.
In an electrochemical cell, the reverse process is happening; spontaneous redox reactions are setup in the cell as the INPUT, in order to PRODUCE a potential difference between the two electrodes. The electrode at which the reduction occurs becomes the cathode, which is positively charged, and the oxidation occurs at the anode, which is negatively charged. Electrons flow from anode to cathode; this is how batteries produce electricity.
To learn more about electrochemistry, take a look at the University of Birmingham resource for A-Level Chemistry:
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