Using a microscale conductivity meter

In this experiment, students can use a series of different materials, and a microscale conductivity meter, to see which material is best at allowing an electrical current to pass through. A group of materials has been suggested, but virtually any can be tested in this straightforward practical. 

This practical should take 15 minutes.

Equipment

Apparatus

• Clear plastic sheet (eg OHP sheet)
• Conductivity meter

Chemicals

• Copper(II) sulfate solution
• Sodium chloride solution
• Tap water
• Deionised water
• Sugar solution
• Copper foil
• Aluminium foil
• Iron nail
• Pencil lead

Health, safety and technical notes

• Read our standard health and safety guidance
• Students must wear suitable eye protection (Splash resistant goggles to BS EN166 3).
• Copper(II) sulfate solution, CuSO₄ (aq) causes eye damage (above 0.12 mol dm^—1), is harmful if swallowed and HAZARDOUS to the aquatic environment (see CLEAPSS Hazcard HC027c).

Procedure

1. Cover the worksheet with a clear plastic sheet. 
2. Add three drops of each of the solutions to the circles indicated on the student sheet provided in the downloads section. 
3. Place a small amount of each of the solids in the circle indicated on the student sheet provided in the downloads section. 
4. Test for conductivity by carefully placing just the tip of the electrodes in each of the substances in turn.
5. Make a table of your results.
6. Give explanations for your results, trying to link the conductivity of a substance with its structure.

Observations

Metals and solutions/liquids that contain ions should cause the light emitting diode (LED) to shine.

This experiment provides a quick and simple method for testing conductivity. The LED will light for any substance – whether liquid or solid – that conducts.