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Code Number: 2A10.30
Demo Title: Surface Tension Balance - Tensiometer
Condition: Good
Principle: Measuring Surface Tension
Area of Study: Fluids
Equipment:
Scale for measuring tension, cup with attached mass, 6 inch plastic Petri dish, small lab jack, cup with spring.
Procedure:
Place the cup with attached mass onto the scale in place of the pan. Zero the scale. Place the Petri dish that is 1/2 full of water onto the lab jack and position it under the cup. Raise the lab jack until the surface of the water touches the cup rim, and then adjust the jack up or down until the balance is re-zeroed. Now turn the dial of the scale up slowly. If done correctly, the cup should break free of the water surface when you reach 4.9 to 5 grams (4900 dynes).
An effective but non-quantitative way to demonstrate this is to just attach a spring to the cup. Measure how far the spring is stretched with just the cup hanging onto it, and then touch the rim of the cup to the surface of the water. You should now have to stretch the spring about twice the initial distance before it breaks free from the water surface.
References:
- Alem-Mar B. Goncalves, Welica P. S. Freitas, Diego D. Reis, Cicero R. Cena, Diego C. B. Alves, Doroteia F. Bozano, "Surface Tension Measured with Arduino", TPT, Vol. 57, #9, Dec. 2019, p. 640-641.
- Julius H. Taylor, "Tensiometer", TPT, Vol. 10, # 8, Nov. 1972, p. 478.
- J. Pellicer, V. Garcia-Morales, L. Gaunter, M. J. Hernandez, and M. Doiz, "On the Experimental Value of the Water Surface Tension Used in Some Textbooks", AJP, Vol. 70, # 7, July 2002, p. 705.
- S. Y. Mak and K. Y. Wong, "The Measurement of Surface Tension by the Method of Direct Pull", AJP, Vol. 58, #8, Aug. 1990, p. 791.
- George M. Hopkins, "Molecular Actions", Experimental Science, p. 56.
- R. W. Pohl, Physical Principles of Mechanics and Acoustics, p. 171.
- Yves Pomeau and Emmanuel Villermaux, "Two Hundred Years of Capillarity Research", Physics Today, March 2006, p. 39.