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Electrochemistry is a branch of physical chemistry that studies the relationship between electricity and chemical change. It encompasses chemical reactions that create electricity and the chemical changes that result from electricity. These processes occur through the transfer of electrons between substances.

At the heart of electrochemistry are redox reactions, which involve oxidation and reduction. Oxidation is the loss of electrons, while reduction is the gain of electrons. These two processes always occur simultaneously. In an electrochemical system, these reactions are separated spatially, allowing for the flow of electrons through an external circuit.

Electrochemical cells are devices that harness these redox reactions. There are two main types: galvanic (or voltaic) cells and electrolytic cells. Galvanic cells produce electricity from spontaneous chemical reactions, such as in batteries. Electrolytic cells use electricity to drive non-spontaneous chemical reactions, as seen in electroplating and electrolysis of water.

Key components of an electrochemical cell include electrodes, which are conductive materials where the redox reactions occur, and an electrolyte, which is a substance containing free ions that conducts electricity. The electrodes are typically an anode (where oxidation occurs) and a cathode (where reduction occurs). An external circuit connects the electrodes, allowing electrons to flow from the anode to the cathode.

The study of electrochemistry has numerous practical applications, including energy storage (batteries, fuel cells), corrosion prevention, industrial synthesis, and biosensors. Understanding the fundamental principles of electron transfer and chemical reactivity is crucial for developing and improving these technologies.