PHYS 1201W Lecture Notes - Lecture 15: Contact Angle, Capillary Action, Surface Tension
Document Summary
Liquids have a strong tendency to stay intact. Cohesiveness of liquids results from the attractions among the molecules. Liquids have well defined surfaces that tend to have a minimum surface area. Ripples are suppressed because they increase surface area. Molecules of liquids experience attractive or repulsive interactions with eh molecules of other substances. Cohesive properties of liquids can be changed by the addition of small amounts of other substances. Molecules in oil are hydrophobic and oils will not dissolve in water. Molecules in soaps and detergents are hydrophilic and hydrophobic. Denoted by gamma, defined as the force per unit of length exerted by one surface. A molecule in the interior of the liquid experiences attractive forces due to all of its neighbors which lowers potential energy. A molecule at the surface does not have as many neighbors, potential energy is not as low. Surface molecules arrange themselves so they have as many neighbors as possible.
