Conductivity and concentrations
To determine the relation between current intensity and concentration of a strong electrolyte solution.
The science behind this experiment
Substances that dissociate into ions are called electrolytes. Acids, bases and salts are electrolytes, and their aqueous solutions conduct an electric current. Sodium chloride as a crystal does not conduct, but dissolved in water its Na+ and Cl− ions allow current to flow.
Equipment used
- Digital multimeter — ELE-001
- DC power supply
- 1 × Connecting wire, red — ELE-005, ELE-006
- 1 × Connecting wire, black — ELE-007, ELE-008
- 2 × Crocodile clips — ELE-009
- 4 × Copper electrodes — CHE-018
- 2 × Test cell covers — CHE-021
Chemicals and reagents
- Sodium chloride solutions of different concentrations
- Distilled water
Safety notes
- Be careful when using the power supply and conductive solutions: risk of electric shock.
Questions for students
- Which solution conducts more current?
- Why?
What to expect
0 A current is measured testing distilled water because distilled water does not conduct electricity. Current increases according to the concentration because of the increasing amount of ions present in the solution. A higher value of current is measured every time the solution is replaced with a more concentrated one. As concentration increases a greenish colour appears (due to formation of copper ions in solution) and some bubbles may appear (due to the formation of chlorine gas) at the electrodes. At the cathode (–), some formation of hydrogen occurs because of the reduction of water. At the anode (+), some formation of chlorine occurs because of the oxidation of chloride ions.
Disposal
Dispose of the solutions into the waste container or into the sink.
Run this experiment in your classroom
This experiment is part of ATP Volta — a self-contained mobile science lab that turns an ordinary classroom into a working STEM laboratory, with over 200 experiments in physics, chemistry, biology, robotics and engineering. Gali, the AI tutor built into ATP Connect, guides students through each step and answers their questions at the bench.
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