Thank you for fantastic delivery on the methamatical derivations. Is it possible to do a video on the theory of dropshape analysis for measuring surface tenstion? Especially the mathematical part.
Prof. Martin, Greetings of the day. Thankyou for the great explanation, however I am unable to imagine that can such a situation arise where both phase 1 & phase 2 has equal tension w.r.to solid I.e., theta = 90.
Hello, Prof.Martin! I'm impressed by your lectures, but you explain "interfacial tension" matter a bit incorrectly. The key is in intermolecular interaction. The molecules at the interface are pulled into volume so the average distances between molecules at the interface become large than inside the volume. Due to this increase of distance you have additional increase in potential energy for the molecules at the interface. Moreover the increase in distance is the tension! That is why the matter is called surface tension. So energy per unit area, sigma, is the PROPERTY of the fluid at certain temperature. Surface energy Wsurf=sigma*Area. Moreover, once you explain Young's equation you don't use the equilibrium of border line which surrounds the water droplet, i.e. molecules of the interface of each phase pull the border line due to tension and that is why the balance equation is introduced in such simple form. In other words, tension force, F, is proportional to the length of border line, i.e. F=sigma*length. If you consider a small segment of border line then F=sigma*dL. There is no sense to introduce "broken bonds" or similar physics because these are secondary matters. Having say that I'm really expressed by subsequent course where you 've introduced the percolation matter, snap off and trapping. Your triangle example is very helpful in understanding of layering or swelling of layers while imbibition. Sorry for my runglish, i.e. Russian English!
Thank you for your comment. You are indeed correct in your physical interpretation as to why the interface between two fluids can be considered literally as a tension. Thank you for adding this explanation in the comments. In my video I kept the idea simple as a change in energy following the approach written by a Nobel Prize winner in Physics: 10. Capillary and Wetting Phenomena: Drops, Bubbles, Pearls, Waves, P-G de Gennes, F. Brochard-Wyart and D. Quéré, Springer (2002).
@@BoffyBlunt Thank you, prof.Martin! You actually motivate me to look for the answer. I'm 44 years old, but it sometimes difficult to realise that you missed something in the school and you need to prepare for the lectures for your colleagues. Books on the subject in oil and gas industry are very poor in terms of physics explanation. Wikipedia also gives final result for Young equation without fundamentals in terms of Newton's law, simple sketch with arrows etc. I found thorough explanation in the lectures of school teacher Pavel Victor from Odessa city. He is really genius in explaining the matter with various examples and simple experiments. ru-vid.com/group/PL1Us50cZo25mikFg7yYkpmpNK7tGcub35&si=8Ya9_1Wds98tp1zo
