Define the surface of a liquid.

(N/A) The surface of a liquid is defined as the boundary layer between the liquid phase and the gas phase (or vacuum) or between two immiscible liquids.
It is a thin layer,typically a few molecular diameters thick,where the molecules experience a net inward force due to the imbalance of intermolecular forces.
This imbalance leads to the phenomenon of surface tension,where the surface acts like a stretched elastic membrane.