Video about soap and surface tension

Professor Radhakrishnan showed us how oil and food coloring interacted with water and surface tension. She also discussed how soap works. Soaps are made up of long molecules with one end that loves water, and another that does not. This enables the soap to break apart greasy molecules that are often hard to clean.

I found a video that connects both of these topics. It shows how the surface tension of milk is affected by Softsoap, Gain, Perfect Coat (a dog shampoo), body lotion, and Dirt Devil. In order to see the effects that each different soap has on the milk, the experimenter puts food dye in the milk with a q-tip. The experimenter is able to make intricate designs by adding soap to milk with food dye in it. Each soap the experimenter uses has a different visual effect on the water. I assume the different visual effect each soap has on the water somehow represents the different chemical composition of each soap used.

Milk is unlike water in that it contains more lipids. Soap when added to the surface of milk dissolves the fat and lowers the surface tension in that place. The surface tension of the milk around the soap droplet is higher. The difference in surface tension creates the patterns and colors of the dye in the milk, instead of the colors all just mixing together.

Warning: the music in the video is weird.

https://www.youtube.com/watch?v=X4vA3Agdd6A

http://www.coolscience.org/CoolScience/KidScientists/tiedyemilk.htm