First take a bowl of water and shake some pepper until it covers the water's surface. Did your fingers in the water. Notice anything? Probably not. Then coat a finger in liquid dish soap and stick your finger in the water. What happens? Something pretty cool! Check the video below.
The pepper quickly moves to the edge of the bowl and much of it sinks. Why? Water has surface tension and the pepper flakes do not break this tension. They sit right on top of the surface of the water, not in the water. The liquid dish soap quickly breaks this surface tension and the pepper moves to the side and sinks. It's a simple, yet very cool experiment!