Surface tension

In my experiment, I wish to examine how soap affects the strenght of the surface tension belonging to different, water-based liquids as well as one, non-water based liquid (low surface tension - supervision and control). I will do so by percieving the motion of pepper upon said liquids when the surface tension begins weakening. So, without further adieu:

What is the relatoin between the surface-tension of a liquid and the patterns of motion upon it under the influence of detergent substances?

Watch the video and follow the instructions below.


1) Pour four liquids into flat plates (recycable): oil, orange juice, vinegar and water. 

*Make sure you use an identical amount of each (use a measuring cup).

2) Scatter black pepper on top.

3) Dip a Q-tip/finger in simple, dishwashin soap.

4) Dip the coated Q-tip/finger within the liquid.

What happenes?   

5) Use a ruler to measure the diameter formed (CM).

6) Write down the results. 

Provide an answer by clicking on "Map" and then on "Add an Answer".

Results, Analysis and Discussion
oil juice vinegar water
0 6 7 10
9 14.5 11 17
0 0.5 0.5 0.6

Final conclusion: the higher is the surface tension of a liquid, thus the diemeter formed in its midst is larger under the effect of the detergent.


What is imortant to understand is that surface tension results from a strong attraction between molecules in a liquid and water has a particulary high one compared to most common liquids - like oil. In my experiment, there is a clear, linear correlation between the percentage of water in the liquid and the diemeter formed in the center.

The reason for the formation of the diameter to begin with is thanks to the soap. soap  is a detergent substance who has two polar ends- one hydrophobic and the other hydrophilic. once coming to contact with water, the hydrophobic end scurried along the surface. In the meanwhile, the hydrophilic end is attracted to the water and attempts to from bonds with - thus, effectively reducing the water's tension.

* occaisionally, the diameter formed in the juice can show a larger number then the one in the vinegar - or both can show similiar results. That depends on the specific percentage of water in either one of the liquids as well as the amount of pepper in the specific plate since it absorbs a small amount of the soap.


History of edits
Edited BY: Dana peleg Edit Date: 2017-01-02 17:57:03
Edited BY: Dana peleg Edit Date: 2017-01-02 17:25:17
Edited BY: Dana peleg Edit Date: 2017-01-02 17:22:34
Edited BY: Dana peleg Edit Date: 2017-01-02 17:13:10
Edited BY: Dana peleg Edit Date: 2017-01-02 17:10:27
Created By: Dana peleg Edit Date: 2017-01-02 17:03:51
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