Why does the toothpaste toss the water away from itself when it drops into the sink?
In: Physics
Interestingly, toothpaste is not hydrophobic in nature but actually attracted to water. Toothpaste contains a compound (usually sodium lauryl sulfate) which is surfactant. Surfactants act on the surface of water to alter its surface tension making it bead. Sinks on the other hand are commonly coated with a hydrophobic surface. Therefore. When toothpaste mixes with the water in the sink the water rushes into the tooth paste and the surfactant causes it to bead and be repelled from the sink. What you are seeing are these edges forming from the separation of the toothpaste and water mixture from the sink surface!
Imagine the phenomenon when you see soap droplets in water begin to form beads that appear to be separated from the water but are also mixing with the water!
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