This ‘course-tutorial’ focuses on the study of forces that occur at the molecular level in an interface (liquid-liquid, liquid-solid and liquid-gas). It represents « the study of interactions between chemical species and a surface ». It aims to analyse and identify the properties and characteristics of surfaces and interfaces, and to estimate and calculate the latter. It contains four chapters with a series of tutorials and is intended for second-year students in a professional bachelor's degree programme (L2/S21), specialising in « Oil and Gas Processing Technologies ».