Surface tension test

IloveConverse

Hi guys,

Spent my day doing an experiment to compare two solutions per surface tension.

I just filled up two clear plastic measuring jugs with the two solutions, and recorded how many pins could stay afloat in each solution (100ml).

Then using the equation, F= 2sd or s= F/2d, I attempted to derive a value for each in dyn/cm

So f is force, s surface tension, d is the length of the pin (multiplied by 2 because it has two sides) etc

So, I worked out F, multiplied mass of the amount of pins that each solution can hold by 9.83×10-3 grav. force.

Then to divide by 2d, do I get the length of all the pins in the solution combined and divide by that?


This is really annoying me, and I'm just fustrated at this stage.

basis of the test, except mine is different somewhat http://www.sciencebuddies.org/science-fair-projects/project_ideas/Phys_p012.shtml

Thanks for all replies.

krd

From my reading of the science buddies experiment. d in the equations is the sum of the lengths of all the pins you've used.

But your version of the experiment is a slightly different twist on the science buddies, I'm not sure if it measure surface tension in the same way.

Have you tried it more than once?.....Are you getting a similar number of pins to float each time?

IloveConverse

Are there any other equations that I could use with the test that I'm doing?

Yep, on repeating the test a good few times the amount of pins were on or close to the mean.

krd

IloveConverse wrote: »

Are there any other equations that I could use with the test that I'm doing?

Yep, on repeating the test a good few times the amount of pins were on or close to the mean.

That you're getting results close to the mean on repeating the experiment, means you're definitely measuring something accurately. You are probably getting the surface tension.

The one thing I wonder about the formula, is where it treats the surface of the water as having two sides (the inner surface and the outer surface) - that's where the 2 is coming from. If you did the science buddies version and the results came up double what you have, then in your version you've only broken one surface. All the same I think you have an accurate method of measuring surface tension.

What was the figure you got?

Looking at the Wikipedia page on surface tension, I can see other ways of working it out. But some are really complicated.

But this one looks easy enough. Measuring surface tension with puddles of water on a smooth surface. If you create droplets of water on a smooth surface, you'll notice they all have the same height. Surface tension is holding them in little droplets on the surface. So if you measure the height - and get the density for water at room temperature from somewhere, then you can work out the surface tension.



http://en.wikipedia.org/wiki/Surface_tension Puddles on a surface.

IloveConverse

krd wrote: »

That you're getting results close to the mean on repeating the experiment, means you're definitely measuring something accurately. You are probably getting the surface tension.

The one thing I wonder about the formula, is where it treats the surface of the water as having two sides (the inner surface and the outer surface) - that's where the 2 is coming from. If you did the science buddies version and the results came up double what you have, then in your version you've only broken one surface. All the same I think you have an accurate method of measuring surface tension.

What was the figure you got?

Looking at the Wikipedia page on surface tension, I can see other ways of working it out. But some are really complicated.

But this one looks easy enough. Measuring surface tension with puddles of water on a smooth surface. If you create droplets of water on a smooth surface, you'll notice they all have the same height. Surface tension is holding them in little droplets on the surface. So if you measure the height - and get the density for water at room temperature from somewhere, then you can work out the surface tension.



http://en.wikipedia.org/wiki/Surface_tension Puddles on a surface.

Thanks a million- Sorry for the late reply! Will try this method out.