Notice how the pepper (and the surface water) shot to the perimeter of the dish when soap was added. This happened because soap is a SURFACTANT - a substance that breaks surface tension. The pepper was floating because of the surface tension caused by the cohesion of water molecules on the surface. Imagine having a sheet of rubber stretched tight. If you cut that sheet in the middle, the hole will expand. The water is also attracted to the sides of the petri dish. What property of water is responsible for the water being attracted to the sides of the dish?
Cohesion
Adhesion
Surface tension
Heat capacity