premise: Water, the most common liquid used for cleaning, has a property called surface tension. Molecules in the body of the water are surrounded by other molecules, but at the surface a tension is created as molecules are only surrounded by other molecules on the waterside. This tension inhibits the cleaning process, as it slows the wetting of surfaces due to tension causing the water to bead up. This is where water droplets hold their shape and do not spread. For effective cleaning to take place surface tension must be reduced so that water can spread. Surface-active agents, or surfactants, are chemicals which are able to do this effectively.
hypothesis: the molecules on the waterside hinder the cleaning process.