These are called weak electrolytes. We can detect this kind of compound from conductivity measurements. One way to bring meaning is to establish baseline conditions, e.g., what measurements do you get for water without anything in it and what might be typical values for possible categories. For example, water does have a pH and it does conduct electricity. Impurity particularly CO 2 picked up from the air is the source of these readings.
Water also ionizes a small extent again giving background pH and conductivity measurements.
To answer this you need to measure pH and conductivity of distilled water. Another problem when making measurements is how to decide if differences are significant. Experience helps and so does statistical decision making methods. We want you to learn to recognize the difference between large differences due to differences in the system and differences due to randomness in samples. We want you to do this in a qualitative way.