Why Does Pepper Move to the Edge of the Plate in the Soap Experiment?

  • Context: High School 
  • Thread starter Thread starter Oomph!
  • Start date Start date
  • Tags Tags
    Experiment Soap
Click For Summary
SUMMARY

The soap and pepper experiment demonstrates the effects of surface tension on particles in water. When soap is introduced, it reduces the surface tension of the water, allowing the pepper to move towards the edge of the plate rather than sinking. This occurs because the reduction in surface tension does not happen instantaneously across the entire surface, allowing the pepper to be pushed by the remaining surface tension before it fully dissipates. The movement of the pepper is a result of the soap's gradual effect on surface tension, not a complete elimination of it.

PREREQUISITES
  • Understanding of surface tension and its effects on liquids
  • Basic knowledge of the properties of soap and its interaction with water
  • Familiarity with the concept of gravitational force and buoyancy
  • Experience with simple scientific experiments and observations
NEXT STEPS
  • Research the principles of surface tension in liquids
  • Explore the chemical properties of surfactants like soap
  • Investigate the dynamics of particle movement in fluids
  • Learn about the effects of temperature on surface tension
USEFUL FOR

Students, educators, and science enthusiasts interested in understanding fluid dynamics and the physical principles behind everyday phenomena.

Oomph!
Messages
55
Reaction score
0
Hello.
I have a question... I think that you know the experiment with pepper and soap.
(you put water on plate, than you put a lot of pepper on in, than you put on your finger some soap and than you touch the plate). The pepper goes to edge of the plate. Only some of them fall in the water. It happened because the surface tension was reduced by soap. However, if is the surface tension reduced, than is reduced surface force also. The surface force compensated the gravitational force of pepper at the beginning of the experiment. However, now is the surface force reduced, so it can not compensated the gravitational force. If it is right, the all pepper had to fallen to water, but it is not true, the pepper went to edge of the plate.

Pls, can you tell me why the pepper went to edge of plate? Don't send me a link to wikipedia about surface tension. I understand. I want a straight answer to this problem.

Thank you very much!
 
Physics news on Phys.org
The soap doesn't remove surface tension everywhere instantaneously and totally. It takes time for the area with reduced surface tension to cover the whole surface. I believe what happens is that the pepper moves faster than that area can expand.
 

Similar threads

Graduate How does water rise along a glass plate? (surface tension question)
  • · Replies 2 ·
Replies
2
Views
2K
Fluid Dynamics: Maximizing Downforce Between a Robot and the Floor
  • · Replies 18 ·
Replies
18
Views
3K
A practical way to vaporize fuel for high MPG?
  • · Replies 35 ·
2
Replies
35
Views
3K
Graduate Why does the potential of A decrease when plate B is nearby?
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad Why do wet things stick together?
  • · Replies 2 ·
Replies
2
Views
10K
Try Soap-Free Bathing: Richard's Experiences | Free the Animal
  • · Replies 27 ·
Replies
27
Views
6K
What is the Tidal Bulge Theory and its Controversies?
  • · Replies 13 ·
Replies
13
Views
3K
Undergrad Why Does Charge Flow Between Capacitor Plates When Shorted?
  • · Replies 10 ·
Replies
10
Views
4K
Why Does Detergent Cause a Cotton Loop to Expand on Water?
  • · Replies 3 ·
Replies
3
Views
3K
Why Does Slide Thickness Affect Surface Tension Measurements?
  • · Replies 9 ·
Replies
9
Views
4K