Surfactant

The magic of soap

Before performing this experiment, try the penny and paper clip experiments.

Question

What does soap do to water?

Materials

A bowl, preferably glass.
Water
Pepper
Dishwashing liquid
A toothpick

Procedure

  1. Fill the bowl halfway with water.
  2. Sprinkle pepper evenly on top of the water. (Write down your observations. Does the pepper float? Sink? Stay spread out? Clump together?)
  3. Dip the toothpick in some dishwashing liquid.
  4. Touch the toothpick to the water in the middle of the bowl.

Discussion

When you first sprinkled on the pepper, did it float or sink? Why?
Describe what happened when you touched the soapy toothpick to the water.
Using the words cohesion and adhesion, describe what you saw.

 

For more information you can read up on the topic.

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