Physics in Focus: The Surface Tension Phenomenon
by Yuvi K - December 16, 2023
Surface Tension: An Overview
Surface tension is the phenomenon by which the molecules of a liquid, in an effort to minimize their surface area, draw together to form a skin-like film on the surface, giving the effect of a solid-like object. This physical property of fluids is often seen in everyday life, from rain drops on the window pane to freely-floating bubbles and droplets.
What Are The Factors That Affect Surface Tension?
The magnitude of the surface tension of a liquid at a particular temperature depends on a number of factors, including the nature of the liquid, its temperature, surface area, and the presence of any additives present in the system.
Physics behind Surface Tension: The Molecules Perspective
The phenomenon of surface tension is caused by the attraction between liquid molecules. Every molecule has an unequal attraction for the liquid around it, which is known as surface energy. This creates an internal pressure within the liquid that causes the molecules to draw together on the surface and form a thin film. As a result, the entire liquid behaves as though it has an elastic skin on its surface.
Examples of Surface Tension
Surface tension is commonly seen in everyday life, such as:
- Early morning dew drops on a blade of grass
- Floating paper clips on a bowl of water
- The rise of mercury in a thermometer
- The difficulty of cleaning a greasy pan
- Insects and small objects that can walk on water
How Can We Measure Surface Tension?
Surface tension can be measured using various instruments. Some of the more common instruments used to measure surface tension are:
- Du Noüy Ring Method (डु नूए रिंग विधि): This is an equilibrium measurement technique where a small ring is placed on a liquid surface and a spring force is applied. The spring force is measured and the surface tension of the liquid is calculated.
- The Wilhelmy Method (विल्हेल्मी विधि): This technique is used to measure the surface tension of thin films. It uses a balance to measure the force required to draw a plate across the thin film. The surface tension is calculated based on the force needed.
- Drop Volume Method (ड्रॉप वॉल्यूम विधि): In this method, the volume of a drop of liquid is measured and the surface tension is calculated based on the radius of the drop.
Conclusion
Surface tension is an interesting and important physical property of fluids that affects many aspects of our daily lives. Through a better understanding of the forces that create surface tension, we can use this phenomenon to our benefit in many ways.
