By dissolving ions in water, the overall resistance of the water is reduced, increasing the conductivity. .
Many factors contribute to the conductivity of water. Of course, the local geography of an area will determine the base level of conductivity. As a result, when speaking of the conductivity of a substance, one generally refers to the specific conductivity. Other sources of ions also exist. Pollution from urban areas, salts applied to roads, and agricultural runoff are a few examples of man's contributions. Many natural factors besides the local geography are also involved, such as rainwater from ocean sources, evaporation as it leaves a higher concentration of ions behind, and bacterial metabolism. Because of the abundance of sources for ions, conductivity is not the most specific test of a water source's quality. However, it serves as an indication that something has contributed to the ionic concentration of the body of water, so it can be useful as an easy test to determine changes in quality. .
Experimental Design.
The experiment was designed to study the effects of three different variables on the conductivity of distilled water. Distilled water, through purification processes, has a relatively low conductivity due to the removal of many ions. Therefore, changes in the conductivity should be easy to detect. The first variable examined was the effect of different types of soil samples on the conductivity. One sample was taken from a pile of dirt outside my apartment complex. The other sample it was compared with was taken from a typical bag of potting soil. A second variable was the amount of each soil type used in the experiment. I therefore used samples of five, ten, and fifteen grams for each type of soil. The final variable for this experiment was the amount of time that the soil was introduced to the water. .
Exposing the soil to the water was the difficult part of the experiment.