Membrane saponose e loro tensione superficiale

Soap bubbles and soap films are interesting and amusing. This article describes an experiment on soap films which can be used at secondary school level that involves forming a film with the shape of a deformed quadrilateral in an area bounded by two rigid straws and two pieces of thread of equal length attached to their ends (Fig. 1). By means of a theoretical demonstration we derive an equation that allows to obtain the surface tension of the soap solution within a precision of about 10%. From a pedagogical point of view, this activity could make pupils reach a deeper understanding of the behavior of the surface tension forces.