Electrochemistry

Electrochemistry is the study of the relationship between chemical reactions and the flow of electric current. It centres on reactions in which electrons are transferred between substances — oxidation, the loss of electrons, and reduction, the gain of electrons. When such a reaction is arranged so that the electrons travel through an external wire rather than passing directly between particles, chemical energy can be converted into electrical energy, or vice versa.

A device that does this is an electrochemical cell. In a galvanic, or voltaic, cell a spontaneous reaction drives electrons from one electrode to another, producing a usable voltage; this is the principle behind batteries. A classic teaching example is the Daniell cell, in which a zinc electrode in a zinc-salt solution is connected to a copper electrode in a copper-salt solution, with zinc dissolving and copper depositing as current flows. The lead–acid accumulator used in vehicles and fuel cells, which combine hydrogen and oxygen to generate electricity, work on related principles. The reverse process, electrolysis, uses an external current to force a non-spontaneous reaction, as in splitting water into hydrogen and oxygen.

These ideas are well suited to animation, since the underlying events — metal atoms dissolving into ions, ions migrating through a solution, and electrons moving through a circuit — cannot be seen in a real cell. Simulations of a voltaic cell or an electrolysis apparatus let learners follow the charge carriers and connect the visible voltage or current to the chemistry occurring at each electrode.

Frequently asked questions

What is the difference between a galvanic cell and electrolysis?

A galvanic cell uses a spontaneous reaction to produce electricity, while electrolysis uses an external electric current to drive a reaction that would not happen on its own.

What is a Daniell cell?

It is a classic galvanic cell pairing a zinc electrode with a copper electrode in their respective salt solutions; zinc dissolves and copper is deposited as current flows.

How does a fuel cell generate electricity?

It combines a fuel such as hydrogen with oxygen in a controlled electrochemical reaction, producing electric current and water rather than burning the fuel.