Abuzz
Posts: 1
Joined: Thu Mar 07, 2013 6:50 pm

### Surface tension of water ? Help !

Okay So I'm Doing A Science Project On The Surface Tension Of Water , & I'm Going To test it on a penny . But what could be a way i could put it into a scientific question ? And what would be the manipulated and responding variable? Thank you

theborg
Moderator
Posts: 350
Joined: Mon Oct 03, 2011 12:26 pm
Occupation: US Air Force Space & Missile Operations

### Re: Surface tension of water ? Help !

Abuzz,

Welcome to science buddies and thank you for your question. This sounds like a really interesting project.

Surface tension of a liquid is the result of the cohesive force between molecules of that liquid at the surface. Typically individual molecules in a liquid is surrounded on all sides by other molecules and they interact with each other in all directions. However, molecules at the surface do not have other like molecules on all sides and consequently they cohere more strongly to those directly associated with them on the surface. This "surface film" makes it more difficult to move an object through the surface and is known as surface tension. It is measured in dynes. 1 dyne = 0.00001 newtons. It would help if you had a way to measure this directly.

You need to determine what physical property of surface tension you are looking to test. Then you will know what your independent (manipulated) and dependent (responding) variables will be.

For example, you could hold your weight the same (i.e. your penny) and vary the liquid in some way to determine how the surface tension changes. You can do this by using different liquids (or water with various levels of salt concentrations) or by taking the same liquid, like water, and changing the temp to see if temperature has a significant effect of the surface tension (i.e. does ST increase or decrease with an increase in temperature from 0 to 100 deg C).

Let I see that your project was due on 12 March. I hope this is still helpful. Please post back if you have additional questions.
Hope this helps.

theborg
----------
Science Buddies science fair guide:
http://www.sciencebuddies.org/science-fair-projects/project_guide_index.shtml

Science Buddies project ideas:
http://www.sciencebuddies.org/science-fair-projects/project_ideas.shtml