What force is responsible for the spherical shape of liquid droplets and their ability to keep this shape when placed into an aerosol suspension?
a. Cohesion
b. Adhesion
c. Viscosity
d. Surface tension
ANS: D
Surface tension is a force exerted by like molecules at a liquid's surface. A small drop of fluid provides a good illustration of this force. As shown in Figure 6-8, cohesive forces affect mole-cules inside the drop equally from all directions. However, only inward forces affect molecules on the surface. This imbalance in forces causes the surface film to contract into the smallest pos-sible surface area, usually a sphere or curve (meniscus). This phenomenon explains why liquid droplets and bubbles retain a spherical shape.
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