Variation in the molecular properties of different liquids, illustrated by water (dyed red) and drops of mercury on a glass plate. The attractive force between molecules of the same substance is called cohesion, as distinct from the force of adhesion between different molecules. Here, adhesion of water to glass is stronger than cohesion in water mercury, however, cohesion is stronger than its adhesion to glass. Mercury spilled on glass therefore forms spherical or flattened droplets.