ABSTRACT
The influence of surfaces on the bulk behaviour of materials depends on the ratio of surface area to the total mass. This in turn depends partly on the size and partly on the shape of the individual particles making up the bulk material. All surfaces have one thing in common: the atoms or ions in the surface are subjected to asymmetric or unsaturated bonding forces. Since bonding is taken to lower their energy, the surface atoms or ions will be in a state of higher energy than interior ones. Surface tension differs from an elastic force acting between the surface atoms in that it remains constant whether the film is forced to expand or allowed to contract. The ability of adhesives to spread and thoroughly wet surfaces is critical. The ability of liquids to wet solids depends very much on the cleanliness of the solid, as anyone with any experience of soldering will appreciate.
