Build a Saltwater Circuit

Did you know that you can use salt water to make a light bulb illuminate? This is because saltwater is a good conductor of electricity which makes ocean water a resource for renewable energy. Salt molecules are made of sodium ions and chloride ions.

Salt molecules are made of sodium ions and chloride ions. 

An ion either has a positive OR a negative charge based on whether it has gained or lost an electron. Gaining an electron equates to the atom having a negative charge and losing an electron gives the atom a positive charge. 

When you put salt in water, the water molecules pull the sodium and chlorine ions apart so they are floating freely, increasing the conductivity. These ions are what carry electricity through the water with an electric current. In short, saltwater (water + sodium chloride) acts as an electrolyte to transfer the electrical energy (current) through the water. While this can be done on a large scale, let's try a small-scale fun science project to see how it works! A project like this would make a great science fair project for elementary or middle school. 

What You Need to Build a Saltwater Circuit:

Build a Saltwater Circuit in 8 Easy Steps

Wrap two tongue depressors in aluminum foil. These will be your electrodes.


Cut three 6-inch pieces of insulated copper wire and strip a half-inch of insulation off each end.


Connect one end of a wire to the positive terminal of the battery - hold it in place with alligator clips. (If you are using a battery cap, connect it to the red wire.) Connect the other end of the wire to the light bulb socket. (Just wrap the wire around the bottom of the bulb, if you don't have a socket. You may have to secure it with tape.)


Take the second piece of wire and connect the light bulb socket with one of the electrodes. Use masking tape to stick the bare end of the wire on the aluminum foil near the top of the electrode.


Use the third piece of wire to connect the negative terminal of the battery with the other electrode.


Test out your circuit by touching the two electrodes together. This should complete the circuit and allow electricity to flow from one terminal of the battery to the other, lighting up the light bulb in the process. If the bulb doesn't light up, check your wire connections to make sure they are all secure, and then try again.


Pour one cup of water into a cup or beaker. (If you have distilled water, that will work best.) Put the two electrodes in the cup, but don't let them touch each other. What happens to the light bulb?


Remove the electrodes from the cup and then stir in a teaspoon of salt until it dissolves. Put the electrodes in the saltwater without touching them together. Watch the light bulb.


Circuit Kits to Take Learning to the Next Level

Science Lesson:

    The light bulb lit up because the sodium and chlorine ions conducted the electricity (an electrical current) from one electrode to the other.  

    The negative electrode is the anode and the positive electrode is the cathode. The electrons naturally flow from the negative anode toward the positive cathode because the electrons are negatively charged. The flow of electrons through that wire is electricity.  

    This completed the simple circuit, causing the light bulb to illuminate. 

    Try adding more sodium chloride (salt) and see if the light bulb illuminates brighter. Use a buzzer instead of a light bulb and see if more or less salt in the water makes the buzzer ring louder or softer. 

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