ADULT SUPERVISION REQUIRED.

Set up a simple six-volt circuit with a light bulb. Separate the free wires, and dip the ends in fresh water, then in a salt water solution. You will see that the salt water allows the light to light up.

Now repeat the activity, beginning with fresh water and adding salt spoonful by spoonful until the light comes on and then gets brighter and brighter. Next, slowly move the free ends of the wires in the salt solution further apart.

Salinity (the amount of salt) in water is sometimes measured by the brightness of the light generated in just this kind of circuit.

If possible, obtain some ocean water, and compare the brightness of the light generated in ocean water to the brightness in the previous tests.

(Note: In some areas hard water will conduct electricity, and distilled water should be used instead of tap water in the initial tests.)

Does the salt water make those blind fish have bright colors that are like lights?