Surface Tension

Meghan added three different food colours around the bowl of milk so they were not touching. Next she dipped the skewer into some dishwashing liquid. Then she dipped the skewer into the milk a few times. Suddenly the food dyes moved through the milk even though she did not stir it. She did the same thing with a bowl of water sprinkled with pepper. When she put the dishwashing liquid dipped skewer into the bowl the pepper literally zoomed to the outside of the bowl.

So what’s happening?

Dishwashing liquid reduces the surface tension of the milk. This lets the particles of milk at the at the surface to spread out more. As the particles spread out they push the food colouring/pepper out as well. The dyes then merge together to make patterns.