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Electrolysis being used in a laboratory Electricity can be used to separate a chemical compound into the molecules that make it up. This process is called electrolysis. For it to work, the compound has to conduct electricity, it must be in liquid form (molten or in solution) and it must contain ions (electrically charged atoms), that are free to move about. Two rods, made of conducting material such as carbon or a metal—the electrodes—are placed in the liquid compound, called the electrolyte. An electrical current is then passed through the liquid. The negative ions in the compound are attracted to the positively charged electrode, called the anode, while the positive ions move to the negatively charged electrode, the cathode.

The electrolysis of water using a voltameter

Electrolysis of water

Water, a compound (H2O), can be broken down by electrolysis into molecules of oxygen (O2) and hydrogen (H2). When an electric current is passed through the water, negative hydrogen ions are attracted to the cathode, the negatively charged electrode. Here, electrons from the cathode are given to the hydrogen ions to make neutral hydrogen gas (this is a reduction reaction). Meanwhile the negative oxygen ions are attracted to the anode, the positively charged electrode. Here, the oxygen ions give up their electrons to form neutral oxygen gas (this is an oxidation reaction). Because water contains two hydrogen atoms for every oxygen atom, twice as much hydrogen gas as oxygen gas is produced. In a voltameter, the gases bubble up through the water to collect in tubes above both the cathode and anode.

Electrolysis can be used for removing unwanted hair from the body. The body itself is the electrolyte, while a device called a galvanic epilator delivers a tiny electric current. Sodium hydroxide, which forms at the the needle-shaped probe—the cathode—kills the hair cells.

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