From a chemistry andor physics point of view. How do you explain pepper repelling from dish soap?

Tuesday, May 5th, 2009 | Chemistry

Mike asked:


You know when you put ground pepper ontop of water in a dish.

The pepper floats on top, covering the water. But when you put some dishwater soap on your finger and stick it in the middle of the dish, The pepper moves away from the finger.

How do you explain this in terms of chemistry and physics?

Related posts:

  1. How do I explain the physics of an egg drop? nancy c asked: For my egg drop project, me...
  2. What can you find out about go karts you can explain in physics? Tana c asked: I need imformation on the go...
  3. What is the chemistry of cat urine and how does hydrogen peroxide 3% work to get rid of the odor? Jon G asked: I learned (and saw for myself)...
  4. What are the physics behind a homopolar motor? How does a homopolar motor work? and why? golden c asked: In physics terms, can someone please...

Tags: , ,

Related posts:

  1. How do I explain the physics of an egg drop? nancy c asked: For my egg drop project, me...
  2. What can you find out about go karts you can explain in physics? Tana c asked: I need imformation on the go...
  3. What is the chemistry of cat urine and how does hydrogen peroxide 3% work to get rid of the odor? Jon G asked: I learned (and saw for myself)...
  4. What are the physics behind a homopolar motor? How does a homopolar motor work? and why? golden c asked: In physics terms, can someone please...

1 Comment to From a chemistry andor physics point of view. How do you explain pepper repelling from dish soap?

ChatNoir
May 8, 2009

The answer is on this site:

The “simple” answer is that the surface tension of the pepper particles is less than “pure” water (about 72 ergs/cm^2), so the pepper particles tend to float on the water’s surface. When you add a drop of soap, you greatly reduce the surface tension of the water near the point at which you add the soap. Initially, this causes a repulsion of the pepper particles and the particles tend to follow the high surface tension areas. If you shake the solution, you will find that the pepper particles get “wetted” by the soap solution and the pepper will disperse in the soap solution.

Leave a comment

You must be logged in to post a comment.

Search