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Simple Electrolysis

This time, we are going to do a very quick and easy demonstration of electrolysis, and learn some chemistry at the same time.

You will need:

  • a nine volt battery
  • aluminum foil
  • water
  • salt
  • a plastic cup
  • turmeric (a spice)

Fill the cup about 2/3 with water. Add a heaping spoon of salt, and stir until it is dissolved. Tear two thin strips of foil. Crumple one end of a strip around one terminal of the battery. Crumple one end of the other strip around the other terminal of the battery. Sprinkle a little of the turmeric on the surface of the water. Then stick the two free ends of the foil into the saltwater.

As soon as the foil hits the water, things start to happen. You get lots of bubbles rising from the strip that is attached to the negative terminal, and a few bubbles rising from the strip attached to the positive terminal. After a few seconds, some of the turmeric between the two strips begins to turn red.

What is happening? Through a process known as electrolysis, the electric current separates the water into hydrogen (H+) and hydroxide (OH-) ions. The table salt separates into sodium ions (Na+) and chlorine ions (Cl-). The positive ions (H+ and Na+) are attracted to the negative terminal on the battery. The hydrogen ions combine to form bubbles of hydrogen gas. That is what causes all the tiny bubbles that fizz up from that side of the battery.

The negative ions (OH- and Cl-) are attracted to the positive terminal on the battery. The chlorine ions combine with the copper to form green copper chloride.

The remaining sodium ions combine with the hydroxides to form sodium hydroxide, commonly known as lye. Since sodium hydroxide is alkaline, you can easily detect it by sprinkling a little of the spice turmeric on the surface of the water. Usually turmeric is yellow, but in the presence of an alkaline substance, such as sodium hydroxide, it turns red.