ABSTRACT
The concepts of ‘interface’ and ‘surface tension’ are very important in colloid and surface chemistry, with many phenomena like capillarity, the existence of bubbles and drops depending on them. An interface is a two-dimensional plane, frontier or boundary, with no thickness, formed at the meeting point of two surfaces. Surface tension is force per unit length, acting perpendicularly at the surface of a bulk liquid phase. First, the chapter introduces the concept of interfaces and describes how they are formed. This is followed by a description of the types of interfaces and their typical examples. Second, the concept and origin of surface tension are given together with a detailed description of its measurement using the Wilhelmy plate, the du Noüy ring, the maximum bubble pressure, the capillary rise, the drop volume or weight, the pendant and sessile drops methods as well as spinning drop tensiometry and other methods. In addition to these, the chapter discusses the phenomena of capillarity and wicking, the origin and consequences of drops and bubbles formation. Lastly, solved examples along with end-of-chapter questions are given to help the reader appreciate the use of some of the mathematical equations derived during the presentation of the various concepts.
