Turning Electricity into Matter
Electrolysis is the process of using electrical current to drive a non-spontaneous chemical reaction. When you pass current through a solution of copper sulfate, copper ions in solution gain electrons at the cathode and plate out as solid metal. Michael Faraday quantified this in the 1830s, establishing laws that remain the foundation of electrochemical engineering two centuries later.
Faraday's Quantitative Laws
The first law states that mass deposited is proportional to charge (m ∝ Q), while the second law states that for the same charge, the mass deposited is proportional to the equivalent weight M/z. Together they yield m = MIt/(zF), a remarkably precise equation. In practice, if you know the current, time, molar mass, and valence, you can predict the deposited mass to within a few percent.
Industrial Scale
The aluminium in every aircraft wing was produced by electrolysis. The Hall-Héroult process dissolves alumina in cryolite and passes enormous currents (100,000+ amps) through the melt. Aluminium smelting consumes roughly 5% of all electricity generated in some countries, making Faraday's laws relevant not just to chemistry but to energy policy and economics.
Electroplating and Beyond
Beyond bulk metal production, electrolysis enables precision applications: chrome plating for durability, gold plating for electronics, and anodizing aluminium for corrosion resistance. Electrochemical machining uses controlled dissolution to shape hardened steel with micron precision. In each case, Faraday's laws predict exactly how much material moves per amp-second.