All About Capillary Rise

Capillary action is the ability of a liquid to flow in tiny places even without external variables like pressure or in contrast to them. Liquids could be drawn up between the hair of a paintbrush, in a small tube, in porous materials such as paper and plaster, in non-porous substances like fine sand and fluid fibreglass, or in a cell. This is caused by molecular interactions between the fluid and the adjacent solid surfaces. The liquid is pushed by interfacial tension and adhesion forces between the liquid and the vessel surface if the capillary tube’s width is narrow enough.

Use of a capillary tube

The use of a capillary tube to demonstrate the phenomenon is common. A concave meniscus forms whenever the minimum rate of a straight glass tube is soaked in a liquid, such as water. The liquid column rises due to adhesion between both the fluid and the solid inner surface until there is enough fluid volume for gravity force to overcome intermolecular interactions. The current contract (around the edge) here between the top of the liquid column and the tube is proportional to the tube’s radius, but the weight of the liquid column is equal to the square root of the tube’s radius.

Capillarity in Everyday Life

(i) Kerosene oil in a lantern and melted wax in a candle rise through the cotton wick’s capillaries and burn.

(ii) Coffee powder is quickly soluble in water because capillary action instantly wets the small granules of coffee.

(iii) The water applied to the fields rises through the numerous capillaries produced in the stems of plants and trees to reach the leaves.

(iv) The tip of a pen’s nib is split to allow ink to ascend through capillary action.

(v) The capillary action of cotton in the towel is responsible for a towel’s ability to absorb moisture from the body.

Cohesion and Adhesion

Intermolecular forces, which are attractive force interactions among individual particles inside a sample, are experienced by the molecules in just about any sample of matter. Many observable characteristics of substances, such as the phase they are in certain pressure and temperature conditions, are caused by such forces. Since they hold the particles of a sample closely together, cohesive forces, or forces that result in cohesion, emerge when attractive forces occur between molecules. Surface tension is caused by these cohesive forces being especially strong near a liquid’s surface. Hydrogen bonds between water molecules, for example, are essential for the cohesion seen in water droplets.

Intermolecular forces are known as adhesive forces whenever they happen between distinct molecules (particularly once they are part of separate states of matter). The particles in a water sample in interaction with a glass surface are attracted to the glass molecules by attraction forces. For these interactions, water has a habit of sticking to such surfaces.

Capillary Action in Water

We understand that whenever a liquid is poured into a vessel, the free area of the liquid along the curves of the walls upwards, either concave or convex. Because the bore of the capillary tube is so narrow, all of the spots on the outer surface are extremely close to the walls, making the entire free surface curve. It’s known as a meniscus. The meniscus of a glass capillary submerged in water is concave upwards. The atmospheric condition is the air pressure on the top or curved side of the meniscus. The force on the convex side of the outer surface will be less than the force on the concave side, as we know. It signifies that the force underneath the meniscus, on the convex side, is lower than air pressure. Atmospheric pressure exists just beneath the level surface of the water in the surrounding vessel. As a result, the system is out of balance, and the liquid rises in the capillary tube until it reaches equilibrium.

Surface Tension

Surface tension is the force applied to a liquid’s surface layer due to the surrounding liquid’s attempt to reduce the surface area by pulling on surface particles. When the liquid’s surface is sufficiently strong, surface tension is used. It can bear a significant amount of weight.

Determination of the Surface Tension of Liquid

A beaker of liquid (for example, water) with the surface tension to be measured is dipped in a capillary glass tube. Surface tension causes the liquid level inside the capillary to rise. This process is known as capillary action or capillarity.

A travelling microscope is used to concentrate on the bottom meniscus of the curved concave surface. The reading is taken under a microscope. The microscope is lowered into the beaker, and the water level is focused on.

Conclusion 

This article explains capillary rise. Capillarity is the phenomenon of a liquid column rising or falling in a capillary tube. We provide a detailed and easy-to-understand sheet on the Physics Notes to help you comprehend the Basic Physics Concepts.