If a water sample has high conductivity, what does that indicate?

• A. There are many dissolved ions or salts.
• B. The water is extremely pure.
• C. The water is very cold.
• D. The water lacks minerals.

Answer: (A)

Conductivity measures how well a solution can carry an electric current, which depends on the presence of dissolved ions. The more ions or salts in the water, the better the solution conducts electricity, so conductivity is high when there are many dissolved ions. Therefore, a water sample with high conductivity indicates there are many dissolved ions or salts, such as Na+, Cl−, Ca2+, or SO4^2−. If the water were extremely pure, it would have very few ions and thus low conductivity; water lacking minerals would similarly show low conductivity. Temperature can affect conductivity, but the main idea here is the quantity of dissolved ions.