Surface Tension and Soap continued

To understand the effect that soap has on surface tension we need to remember what soap is.

Initially, the surface of the water (and therefore, the pin) is pulled evenly in all directions.

When soap is added, the polar end of the soap molecule mixes with the water, while the long, non-polar chain is pulled along. Water is not terribly attracted to the long, non-polar end of soap, but, it has to go somewhere and it will end up in between water molecules. This interferes with the attraction between those water molecules.

If the attraction at that spot is interfered with, the surface of the water (and the pin) will experience an unbalanced force and will be pulled away from the spot where the soap was added.