Based on a related question, some of us are curious about surface tension in liquids commonly used in food and drink. There's a table on Wikipedia containing a tantalizing amount of information, including:
The surface tension of water decreases from 76 mN/m to 59 mN/m as temperature increases from 0C to 100C. It's 72 mN/m at warm room temperature, 25C.
10% acetic acid (very strong vinegar) has a substantially reduced surface tension (55 mN/m at 30C)
Alcohol can strongly reduce surface tension, to 46 mN/m at 11% and 30 mN/m at 40%.
A concentrated sucrose syrup (55%) has somewhat higher surface tension than water, 76 mN/m at 20C.
Very salty water (6M, compared to seawater at .6M) has higher surface tension, 83 mN/m at 20C.
Of interest would be:
How does surface tension typically depend on temperature? (Does it always decrease with increasing temperature?)
How do various everyday solutes (e.g. sugar) and mixture components (e.g. alcohol, acetic acid) affect surface tension of water? Actual data on measured surface tension of liquids would be wonderful - for example, what is the surface tension of milk, tea, vinegar, syrup, various alcoholic beverages, or anything else we commonly cook with or drink? What determines whether something increases or decreases the surface tension of water?
Are there any more exotic (but edible!) solutes or mixture components with dramatic effects on surface tension? Especially interesting would be ones without flavor, which could be used to tweak existing liquids.
Note: I posted a related question on the physics stackexchange.
This article suggests that starch gives a significant increase, and oil emulsions a significant decrease.
The same principles should apply to any small nonpolar molecule (reduces surface tension) and large molecule (increases surface tension). Note that this generally correlates strongly with viscosity. Forces at the surface forces are generally related to forces in the interior of the liquid.
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