Measuring Surface Tension of Liquid | Methods & Units

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Discussion Overview

The discussion centers around methods for measuring the surface tension of liquids, exploring various techniques and the units used to express surface tension. Participants inquire about the principles behind these methods and the interpretation of measurement units.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant asks about the methods used to measure surface tension and how the units reflect the data.
  • Another participant suggests looking at specific methods, such as the Du Noüy ring method and the Wilhelmy plate method, noting that these methods relate the force needed to detach an object from the liquid surface to the surface tension.
  • A participant questions the meaning of the units mN/m, seeking clarification on their interpretation.
  • It is noted that mN represents 10^-3 N, with the denominator being in meters.
  • One participant proposes that measuring the velocity and wavelength of ripples in a liquid could also provide a means to measure surface tension, indicating that there may be multiple methods available.
  • A mathematical expression for surface tension is presented, suggesting that measuring the force on a unit length line on the surface can yield surface tension, although this is not described as an experimental method.

Areas of Agreement / Disagreement

The discussion includes multiple competing views on methods for measuring surface tension, and no consensus is reached regarding the best approach or the interpretation of units.

Contextual Notes

Participants express uncertainty about the experimental methods and the definitions of units, indicating potential limitations in their understanding of the measurement techniques.

Who May Find This Useful

This discussion may be useful for individuals interested in experimental physics, materials science, or anyone looking to understand the principles behind measuring surface tension in liquids.

derekmohammed
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Hi,

Just a quick question:

How do you meausre surface tension of a liquid? WHat meathods are used and how do the units reflect the data.

Thanks

Derek Mohammed
 
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You might have a look at the following site:
http://www.kruss.info/techniques/methods_overview_e.html#Wilhelmy_Plattenmethode

Here is some further comments on the Du Nuoy ring method and Wuilhelmy plate method:
http://www.ksvinc.com/sigma703.htm

Essentially it seems, each of these methods relies on relating the force needed to detach a simple geometric object from the liquid surface to the surface tension.
 
Last edited by a moderator:
What do the units stand for? mN/m? Newton metres/ Metres??

Thanks
 
mN=10^-3N and the denominator is in metres
 
Presumably you could measure the velocity and wavelength of the "ripples" in a liquid to measure its surface tension, since it provides the restoring force for some waves on the surface. I'm sure there are other ways, though.
 
Numerically Surface Tension (T):

T= \frac{F}{l}

Infact, if you consider a unit length line on the surface of the water and measure the force on it from water on one side will give you Surface Tension. But that's not the 'experimental
method.
 

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