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Conductivity of aqueous solutions
Test of conductivity
if a solution is conductive, a conductivity test is performed. This
test is based on the same principle as the test performed on solid
The aqueous solution is inserted in an electrical circuit comprising a
battery and a bulb that lights when electric current flows and
therefore when the aqueous solution is conductive.
test involves some differences:
- It is necessary to use a vessel containing the tested solution.
This solution is connected to the rest of the circuit using metal rods
that are immersed (these rods are called electrodes).
- The bulb does not light up if the current is too low and it can't
To detect low currents an ammeter is therefore also inserted in the
Electrical circuit diagram used to test conductivity of aqueous
3) Some results of the conductivity test
bulb light ?
of copper sulfate
Test of conductivity: interpretation
is totally insulative but we can nevertheless distinguish two groups
among tested solutions:
- Distilled water, tap water and sugar water for which the electric
current is very low (in general it is considered that distilled water
is an insulator).
- The salt water and the solution of copper sulfate for which the
current is much higher, which indicates they are good conductors of
current is consists of electrically charged particles in motion: it can
then be concluded that distilled water, tap water and sugar water
contain few particles of this kind.
- Pure water contains almost only water molecules which are
- Tap water contains molecules of water and mineral salts.
- Sugar water contains water molecules, molecules of sugar (sucrose
molecules) and mineral salts.
It can be
deduced that sugar water and the solution of copper sulfate are
conductive because they contain electrically charged particles.
These particles are called ions.
sugar water and tap water are not completely insulative because of
their mineral salts that are composed of ions.
Distilled water is not totally insulated as it is not perfectly pure:
it may contain, ions from the atmospheric gases that are dissolved.
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