Students reading a “Caution: Keep away from water!” notice on an electrical appliance may assume all water conducts electricity. Clear up their misconception with this easy-to-assemble conductivity tester that uses a piezoelectric buzzer and emits an audible sound when a circuit is complete. Use the first demonstration to engage students in a lively discussion about why three colorless liquids produce varying sounds—or no sound at all! In the second demonstration, students see and hear the effect concentration has on the conductivity of an electrolyte. The buzzer is sensitive enough to track the diffusion of ions as a few crystals dissolve in solution and form a complete circuit. The conductivity of acids and bases is explored in the third demonstration. Listen to the surprising results when an acid and base are combined! Enough chemicals are provided to perform each demonstration seven times with one reusable conductivity tester.
Concepts: Electrical conductivity, electrolytes vs. nonelectrolytes, ions.
Time Required: 20 minutes
Materials Provided: Ammonia, copper wire, copper(II) sulfate, sodium chloride, vinegar, battery clip with wire leads, Fahnestock clips, Petri dishes, piezo buzzer.
Note: A 9-V battery is required and available separately.
Flinn Catalog/Reference Manual Page 398
Flinn Middle School Catalog/Reference Manual Page 431
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