PHC320H1 Lecture Notes - Lecture 20: Air Interface, Surface Tension, Minimal Surface
24 Mar 2015
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Difference is that molecules of liquid may change shape thereby going for shape with lower volume or surface area/volume ratio but solids cant do that so shape is given. Erg is a unit of energy, 1 erg=10 ^-7 joule. Also second way to define surface tension and it is obvious, in addition to definition in terms of energy, we can define this in terms of force since n is a unit of force. A=2lds there is a 2 since there are two phases thus dw = gamma2lds. So we have 2 definitions of surface tension and both are equilvalent, one is energy and one is in terms of force. Instead of deltaw the ratio deltaw/a, normalize for area and this is =gammals + gammal- gammas then we introduce the spreading coefficient. Spreading coefficient(s) = -dw/a this is equal to gammas-(gammal+gammals) so we call it spreading coefficient.
