Problem 2.81 [Difficulty: 5] Open-Ended Problem Statement: Plan an experiment to measure the surface tension of a liquid similar to water. If necessary, review the NCFMF video Surface Tension for ideas. Which method would be most suitable for use in an undergraduate laboratory? What experimental precision could be expected? Discussion: Two basic kinds of experiment are possible for an undergraduate laboratory: 1. Using a clear small-diameter tube, compare the capillary rise of the unknown liquid with that of a known liquid (compare with water, because it is similar to the unknown liquid). This method would be simple to set up and should give fairly accurate results. A vertical traversing optical microscope could be used to increase the precision of measuring the liquid height in each tube. A drawback to this method is that the specific gravity and co ntact angle of the two liquids must be the same to allow the capillary rises to be compared.
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