The cohesive forces between liquid molecules are responsible for the phenomenon known as surface tension. Surface tension is the tendency of liquid surfaces to shrink into the minimum surface area possible. In the International System, it is measured in Pascal. The molecules at the surface do not have other like molecules on all sides of them and consequently, they cohere more strongly to those directly associated with them on the surface. This forms a surface “film“ which makes it more difficult to move an object through the surface than to move it when it is completely submerged.
The cohesive forces between molecules down into a liquid are shared with all neighboring atoms. Those on the surface have no neighboring atoms above and exhibit stronger attractive forces upon their nearest neighbors on the surface. This enhancement of the intermolecular attractive forces at the surface is called surface tension.
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