# surface energy versus surface tension and contact angles

I am hoping to measure the surface tension between two fluids (salt water and isopropyl alcohol), by measuring the appropriate contact angles, and applying Young's equation: https://en.wikipedia.org/wiki/Wetting#Simplification_to_planar_geometry.2C_Young.27s_relation

As far as I can tell, the surface energy and surface tension are interchangable, however I thought that I should ask people that know better than I do, just to make sure.

• Nope, both are very different things. Sep 9 '20 at 12:55
• So, would the above measurement, together with a capillary measurement suffice to calculate the surface tension? Sep 9 '20 at 12:58
• Surface energy has dimension J/m^2, surface tension has dimension N/m. Their relation is the famous high school formula Work = Force . distance. A liquid with surface tension e.g. $\pu{70 mN/m}$ has surface energy $\pu{70 mJ/m^2}$ Sep 9 '20 at 13:10
• Interfacial tension between two liquids implies that they are immiscible. I don't think you will get a distinct interface between isopropanol and an aqueous salt solution. Sep 9 '20 at 13:34
• @James Gaidis I generally agree, but I had suspician isopropanol can be salted out, similarly as some other alkohols are. This amateur youtube video seems confirming the idea, resulting in 2 clearly distinguished phases.. Sep 9 '20 at 13:55