# Formation of meniscus

If molecules at the surface of a liquid have higher energy and want to minimise the surface area, then why is a mensicus formed which of course increases the surface area?

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–  Qmechanic Feb 17 '14 at 14:51

The reason is that the gas-liquid surface area is not the only surface area that is minimized. The total energy of the system (including only surface energies) is given by: $$E=\gamma_{lg} A_{lg}+\gamma_{sg} A_{sg} + \gamma_{sl} A_{sl}$$
Formation of a meniscus as opposed to a flat surface indeed increases $A_{lg}$, but, due to volume conservation, it lowers $A_{sg}$ or $A_{sl}$ depending on whether the meniscus is curved upward or downward respectively. If for example $\gamma_{sg}$ is very large then it can by energetically favourable to increase $A_{lg}$ in order to decrease $A_{sg}$ and lower the total energy. In this way you can in fact derive the contact angle that will result in the minimum energy state.