Electricity can be created when two different metals are placed in sodium chloride solution. Simple batteries can be made this way. The voltage created is due to ionic chemistry – when a metal is placed into an electrolyte (sodium chloride solution in this case) positive metal ions are formed on its surface. These ions pass into the solution making the electrode progressively more negative. If another metal is set up in the same electrolyte, one electrode will become charged to a greater extent than the other because of their different reactivity. This creates a voltage difference between the electrodes which we measure as electrical power.
Different combinations of metals behave differently and therefore create more or less electricity. This practical enables pupils to investigate which combination creates the most electricity as well as teaching them about ionic chemistry.
Equipment required (per set):
- Small beaker
- Strips of: zinc, copper, iron, lead, magnesium and lead
- Crocodile clips
- Digital voltmeter
- Sodium chloride solution
Strips of these metals are available through usual lab suppliers. Magnesium ribbon can be used as magnesium strips are hard to come by.
Dataloggers equipped with a voltage sensor can be used to monitor the voltage differences between the various metals.