Final answer:
Capillary action involves adhesive forces between the liquid and capillary material and cohesive forces within the liquid itself. Stronger adhesive forces relative to cohesive ones allow liquids like water to rise inside narrow capillaries, a phenomenon useful in scientific, medical, and everyday contexts.
Step-by-step explanation:
Capillary action is the net result of two primary forces: adhesive forces and cohesive forces. Adhesive forces occur between the liquid and the surface of the capillary tube, while cohesive forces are the intermolecular forces that keep the liquid molecules together. When the adhesive forces between the liquid and the capillary wall are stronger than the cohesive forces within the liquid, the liquid is drawn up the capillary tube in a process known as capillary rise.
In this process, if the diameter of the capillary tube is smaller, the liquid can climb higher due to the proportional increase in surface area relative to volume, which allows the adhesive forces to have a greater effect compared to cohesive forces. This elegant balance of forces is exemplified by water climbing up a thin glass tube or the transport of water and nutrients in plants through the xylem cells. Because of capillary action, we observe phenomena such as the wicking ability of towels, thin layer chromatography, and even the maintenance of our eyes' lubrication through the pumping of tear fluid.