Explain the concept of surface tension and its ... - SS1 Chemistry States of Matter Question

Surface tension is a property of liquids that arises due to the cohesive forces between liquid molecules at the liquid-gas interface. It is defined as the force per unit length acting parallel to the surface of a liquid.

 

The significance of surface tension in liquids can be understood through the following points:

-       Surface tension and droplet formation: Surface tension enables liquids to form droplets. Due to the cohesive forces between liquid molecules, liquids tend to minimise their surface area, forming spherical droplets with the smallest possible surface area.

-       Capillary action: Surface tension plays a crucial role in capillary action, the ability of a liquid to flow against the force of gravity in narrow tubes or capillaries. The cohesive forces cause the liquid to rise or fall in the capillary, depending on the relative strength of adhesive forces between the liquid and the capillary walls.

-       Meniscus formation: Surface tension causes the formation of a curved surface at the boundary between a liquid and a solid or a liquid and a gas. This curved surface is known as a meniscus and can be observed, for example, in a glass of water, where the water level is higher at the edges due to the adhesive forces between the water and the glass.

-       Bubble formation and stability: Surface tension is responsible for the formation and stability of bubbles in liquids. The cohesive forces within the liquid pull the liquid molecules inward, creating a thin film across the bubble's surface and allowing it to retain its shape.

 

Understanding surface tension is crucial in various practical applications, such as the functioning of soap bubbles, the rise of water in plants through capillary action, the operation of ink pens based on capillary action, and the use of detergents to reduce surface tension and improve wetting ability.