Science Fair Experiments for Testing Salinity

Testing for salt in water is relatively straightforward.

Making a small circuit to test for salinity is one way to see if water contains salt without having to taste it, which leaves a bitter taste in the mouth. Perform your salt water testing using a basic pair of circuits, which you can also set up on the day of the science fair so your viewers, teachers and judges can see your science in action.

Reading

Read about your experiment, including the constituent parts of the circuit that you will use to test salinity of water, to get a basic understanding of your experiment procedure. In particular, focus your attention on why salt water will make the buzzer in your test sound while regular water will not. Use wide resources for your science fair project, including the Internet as well as library books and articles.

Materials

During this experiment, you will place two similar experiment designs next to one another so you can clearly compare the two conditions. Setup your experiment by placing two transparent plastic cups next to one another 1/2 filling one with tap water and the other with tap water with two tsp. of salt dissolved in. Label your two cups with a marker pen before fashioning your testing probes. Wrap two popsicle sticks in aluminum foil. Tape the red, positive side of the battery to a buzzer with electrical tape. Connect one end of one popsicle stick to the buzzer's black wire before taping the other end to the battery's black, negative wire.

Experiment Procedure

Check that your circuit works by touching the probes together, which should make the buzzer sound. If it does not, check all of your connections to ensure they are secured. First, test the regular tap water by submerging the probes about an inch apart --- make sure they don't touch, as this will inadvertently complete your circuit. Second, test the salt water condition by submerging the probes. The salt in the water will carry the charge between the two probes, causing the buzzer to sound.

Demonstration and Results

Demonstrate your salt water tester by setting up your experiment to repeat on the day of the science fair. Gather your crowd around and demonstrate how your salt water tester works as you explain how the salt, as with all electrolytes, carries electric charge through the water, causing the buzzer to sound. Add a touch of showmanship to your presentation by asking your viewing audience, through a show of hands, to predict whether or not the salt water buzzer will sound.

References

• Edcuation: Does Your Tap Water Have Salt In It?
• PBS Kids: Saltwater Tester
• Education: A Science Fair Survival Guide