Christmas Light Electrolyte

Objective:  Determine whether a substance can carry enough electricity through water to illuminate a Christmas light. A substance that conducts electricity in water is called an electrolyte.

Materials

9V battery
1 old set of Christmas lights
wire cutters
cereal bowl
salt

ProcedureDownload the Word document.

  1. Cut one bulb out of the string of Christmas lights, keeping several inches of wire extending from each side of the bulb.
  2. Cut an extra piece of wire from the string without a bulb.
  3. Strip the plastic coating off the ends of the wire to expose one centimeter of metal.
  4. Connect one of the bulb wires to one of the battery terminals, and the empty wire to the other battery terminal. Use anything you can to keep the connection. Alligator clips are ideal, but paperclips also work.
  5. Test the connection by briefly touching the loose ends of the wires. If the bulb lights, all is well. If it doesn't light, something is wrong with your connection, bulb, or battery. Do not leave the wires directly connected or you will burn out the bulb and/or battery in less than a minute.
  6. Fill the bowl with water.
  7. Dip the loose ends of the wires into the water. Does the bulb light?
  8. Water does not conduct electricity on its own. You need some ions to carry the charge. Dissolve some salt in the water. A spoonful is good.
  9. Dip the loose ends of the wires into the water. Does the bulb light?
  10. Salt separates into sodium ions and chloride ions in water, allowing an electrical charge to pass through. What other substances do you think might do the same thing?
  11. Rinse the bowl and repeat the procedure with other substances. See if these are electrolytes:
    • milk
    • sugar
    • baking soda
    • flour
    • vinegar
    • Gatorade
    • orange juice

Questions

  1. When the bulb lights, what is happening to the wires in the water?
  2. Why do you think the conductivity decreases?
  3. What can you do to revive the conductivity?

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