(N/A) The addition of soap or detergent to water reduces the angle of contact. Dirt particles are trapped within the fabric fibers. The molecules of detergent are hairpin-shaped,with one end attracted to water (hydrophilic) and the other end attracted to molecules of grease,oil,or wax (hydrophobic/dirt). This structure forms water-oil interfaces,which drastically reduces the surface tension of the water. As a result,the water can penetrate the fabric more effectively and lift the dirt away,allowing clothes to be washed easily.
Conversely,a waterproofing agent is added to fabrics to increase the angle of contact between water and the fibers,preventing water from wetting the material.