Density and Surface Tension ```Name: Heather Status: student Age: N/A Location: N/A Country: N/A Date: N/A ``` Question: Does the density of a liquid affect its surface tension? Replies: The quick answer is that no, density and surface tension are not tightly related. You can find examples of all four combinations dense-high-tension, dense-low-tension, low-density-high-tension, and low-density-low-tension. That is not to say there is no relationship though. This question can get very complicated very quickly, so I will try to be brief -- the nature of the molecules involved and how attractive they are to each other or to other molecules (such as on a surface) affect both density and surface energy. Molecules that are strongly attracted to each other tend to have higher surface tension and higher density. However, since molecules can be very different -- small molecules like water, intermediate molecules like organic alcohols, and large molecules like polymers -- and one place on a molecule can be chemically different than another place, many possibilities exist. Hope this helps, Burr Zimmerman It all depends upon the geometry of the liquid setup -- bubbles, foams, flat surface -- the relation between surface tension and density is different for each case. A common arrangement is the rise of a column of liquid in a uniform capillary of radius 'r'. In this case, the liquid will rise in the capillary a height 'h' which is given by: 1/2 x (h x d x g x r) = S. Here, 'd' is the density of the liquid, 'g' is the gravitational constant, and 'S' is the surface tension. This capillary rise is used to measure the surface tension of liquids. A word of caution, however. Because surface tension is a "surface phenomenon" it is subject to minute changes in the liquid, the surface in contact, and other experimental variables -- it is not an easy property to measure accurately. Vince Calder Click here to return to the Physics Archives

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