[amp_mcq option1=”surface tension” option2=”cohesion of the liquid” option3=”adhesion of the liquid molecules and the molecules on the surface of a solid” option4=”all of the above” correct=”option4″]
The correct answer is: D. all of the above
Capillary action is the ability of a liquid to flow in narrow spaces without the assistance of, and in opposition to external forces like gravity. The three main forces that are responsible for capillary action are surface tension, cohesion, and adhesion.
Surface tension is the tendency of a liquid surface to contract into the smallest possible area. This is due to the attraction between the molecules of the liquid. The molecules at the surface of the liquid are not surrounded by other liquid molecules on all sides, so they experience a net inward force. This inward force causes the surface of the liquid to contract.
Cohesion is the attraction between molecules of the same substance. The molecules of a liquid are attracted to each other, and this attraction causes them to stick together. This cohesive force is what holds the liquid together and prevents it from flowing out of a container.
Adhesion is the attraction between molecules of different substances. The molecules of a liquid are attracted to the molecules of a solid surface, and this attraction causes the liquid to wet the surface. This adhesive force is what causes the liquid to rise up a narrow tube.
All three of these forces work together to cause capillary action. The surface tension of the liquid pulls the surface of the liquid inward, while the cohesion of the liquid molecules pulls them together. The adhesion of the liquid molecules to the molecules on the surface of the solid pulls the liquid up the tube. The combination of these forces causes the liquid to flow up the tube against the force of gravity.