Interface Tension

Experiment Setup:

Water basin, Erlenmeyer flask filled with oil, glass rod, dishwashing liquid

The Experiment:

The water basin is filled with water and the Erlenmeyer flask is filled with oil is submerged under the water surface in the basin.

Observation:

If you stir the surface of the oil with a rod, the oil will float to the top of the water surface. When you add dishwashing liquid to the oil, the oil spot on the water surface is dissolved and bubbles of dishwashing liquid sink to the bottom of the basin.

Conclusion:

If the interface is torn, the oil ascends to the water surface and forms an oil slick. The dishwashing liquid parts the oil slick and sinks to the bottom. The oil droplets assemble into an oil slick again.