Electrical Conductivity
Definition and meaning of Electrical Conductivity in chemistry.
Electrical conductivity is a measure of how easily a material lets electric charge flow through it. It is the exact mathematical opposite of a property called electrical resistivity. Materials with high conductivity contain freely moving charge carriers like electrons or ions.
In more detail
In solid metals, conductivity comes from a large group of free valence electrons. These outer electrons move easily through the solid metal when you apply voltage. For ionic chemical compounds, the process of electrical conductivity works quite differently.
Solid ionic crystals never conduct electricity because their charged ions are locked tightly in place. You must melt the crystal or dissolve it in water to see conductivity. This action breaks the rigid structure and frees the individual ions to move around.
The positively and negatively charged ions migrate toward opposite electrical poles. This physical movement of ions carries the electric current through the liquid. Chemists classify dissolved substances as strong electrolytes, weak electrolytes, or nonelectrolytes.
This classification depends entirely on how fully the substance breaks apart into separate ions. A substance that splits apart completely will conduct electricity very well. A weak electrolyte only partially splits and conducts current very poorly.
Scientists use conductivity tests daily to check the overall purity of drinking water. Pure distilled water has almost no ions and conducts electricity very poorly. Any sudden spike in water conductivity warns scientists about dangerous dissolved ionic pollution.
Key facts
| Field | Physical Chemistry |
|---|---|
| SI Unit | Siemens per meter (S/m) |
| Mathematical Opposite | Electrical resistivity |
| Metal Charge Carriers | Free valence electrons |
| Liquid Charge Carriers | Mobile dissolved ions |
| Pure Water Property | Extremely poor conductor |
A simple mixture of table salt and water conducts electricity extremely well. The dissolved sodium chloride completely breaks apart into free Na+ and Cl- ions. These mobile charges easily carry the electric current through the liquid water. In contrast, dissolving plain sugar in water creates a useless nonelectrolyte solution. Sugar molecules stay whole and do not conduct any electricity at all. This simple difference helps chemists easily identify unknown white powders in the lab.
Frequently asked questions
Why does solid salt block electricity but melted salt conducts it?
Solid salt crystals lock their charged ions into a rigid and unmoving grid. Melting the salt frees these ions so they can move and carry electrical current.
What makes a strong electrolyte different from a weak electrolyte?
A strong electrolyte breaks apart completely into mobile ions when dropped in water. A weak electrolyte only breaks apart slightly, leaving fewer ions to carry the current.
Can you use electrical conductivity to test water purity?
Yes. Pure water does not conduct electricity well because it lacks free ions. High conductivity indicates that the water contains many dissolved minerals or ionic pollutants.