Capillarity

Capillarity, also known as capillary action, is the phenomenon where a liquid spontaneously rises or falls in a narrow space, such as a thin tube (a capillary), against the force of gravity. This action arises from the interplay of intermolecular forces within the liquid (cohesion) and between the liquid and the surrounding solid (adhesion). If adhesion is stronger than cohesion, the liquid will rise; if cohesion is stronger, the liquid will be depressed. The height to which the liquid rises or falls depends on factors like the liquid's surface tension, the tube's diameter, and the contact angle between the liquid and the solid surface.

Capillarity meaning with examples

• The classic demonstration of capillarity involves dipping a thin glass tube into a beaker of water. Due to strong adhesive forces between the water and the glass, the water climbs up the tube, demonstrating capillarity. This upward movement is visible proof of the surface tension at play, a crucial aspect of water's behavior. This is a direct result of the differing molecular forces at work.
• In the process of oil absorption by a wick, capillarity plays a pivotal role. The porous structure of the wick provides countless tiny channels, through which the oil rises against gravity, fueled by capillarity. The oil travels upwards to the flame for continuous burning. This constant process is crucial for oil lamps, providing a sustained fuel supply.
• The function of paper towels in the context of liquid spills is a strong indication of capillarity. These towels have many tiny, interlocking fibers that create minute spaces. When a liquid is spilled, it quickly spreads through the paper, utilizing capillarity, driven by its adhesion to the fibers, which makes the surface areas huge. Therefore, the water is absorbed efficiently.
• In botany, capillarity enables plants to draw water from the soil up through their roots and stems, and finally into the leaves. The xylem, the plants' water-conducting tissue, creates tiny vessels that facilitate this upward movement via capillarity. This natural phenomenon of capillary action is essential for plants and their survival and growth.