Did you know that you can use salt water to make a light bulb shine? It sounds crazy, but it's true! 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.
(An ion is an atom that has an electrical charge because it has either gained or lost an electron, also meaning it has a positive charge and a negative 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) can help to produce electricity. 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.
DIY Saltwater Circuit Project
What You Need:
- Cup or beaker
- Masking tape
- Water (can be tap water)
- Insulated copper wire
- Salt (table salt)
- 9-volt battery
- Aluminum foil
- A 3.7-volt light bulb in a socket (or buzzer)
- Tongue depressors (or popsicle sticks)
What You Do:
- 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 masking tape. (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.
How to Test a Circuit in Water
- Pour 1 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.
The light bulb lit up because the sodium and chlorine ions conducted the electricity (an electrical current) from one electrode to the other. This completed the simple circuit, causing the light bulb to shine.
Try adding more table salt and see if the light bulb shines 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.
If you want to try another science experiment, you can complete this solar distillation project to get fresh water out of saltwater and then use your saltwater circuit to test the water you distill! Freshwater won't conduct electricity as well as saltwater.