4.6.2. Applications of Surface Tension

As the name implies that at the interface of the two fluids or fluid with two liquids or fluid and the gas what it actually happens it if you look at it that way that I have the liquid molecules if you look at this figures okay. I have the liquid molecules and this is the free surface I have the gas. So if I look at what is the intermolecular forces is there, okay like for example if fluid is at rest conditions, the molecules at these points is having the attracting force between the surrounding molecules. There is a same molecules are there so the cohesive force are acting on this. So these cohesive force are making these fluid molecules in moment, moment considerations. But when you have the at the surface levels, if you look it that these molecules will have the cohesive force the molecular bounding force between the two like molecules and the adhesive force between the gas molecules and the water molecules.

Surface tension is the phenomenon at the interface between a liquid and gas (or between two liquids) that arises due to the cohesive forces between liquid molecules. At the surface of a liquid, the molecules experience a net inward force because they are surrounded by other liquid molecules below, sides, and above. This creates a 'skin-like' effect that makes the liquid surface behave like an elastic membrane.

Consider a stretched rubber band; it resists any force applied to it, similar to how the surface of water resists forces due to surface tension. This is why small insects, like water striders, can walk on water without sinking.

If you imagine it that if these force, the cohesive force is much larger than the adhesive force what is there. That means the molecules which is at the surface, they are going to have a net imbalance force is going to work it. Like you have a surface when which the top of the molecules they are having a pulling effect of the cohesive forces what is working it or bounding forces is acting on that. So this the surface will act like an elastic membranes.

When cohesive forces (forces between similar molecules) exceed adhesive forces (forces between unlike molecules), the surface of a liquid experiences a net inward pull. This imbalance leads to the phenomenon we call surface tension. The analogy used here is helpful: just as a stretched elastic material pulls back when you apply pressure, the surface behaves similarly, creating tension within the liquid surface.

Think about a soap bubble. The film of soap has a layer of water on it, where cohesive forces create a tension that keeps the bubble intact and spherical. Just as a balloon keeps air inside due to its surface tension, liquids shape themselves to minimize surface area.

So that is why small insects can walk on the waters, because of the surface tension forces that what is give the force component because of that small insect can they can walk on the on a water and even if they are having the density is more than that, that is because of the surface tension forces that what resulting surface tension force can result in that ones.

Surface tension is not just a theoretical concept but has tangible applications in nature. It enables certain insects, such as the water strider, to walk on water without sinking. This is possible because the surface tension force is strong enough to support their weight, despite the insects themselves being denser than water.

Imagine trying to balance on a tightrope. The thinner the tightrope, the more careful you need to be. Similarly, water striders balance on water's surface tension, which is the 'tightrope' they walk across.

As a result of these effects, the force what will be resultant per unit length will define as a surface tension forces okay. So this is what it happens it. Because of that if you look at the small insects they can walk on the waters, because of the surface tension forces that what is give the force component because of that small insect can they can walk on the on a water and even if they are having the density is more than that, that is because of the surface tension forces that what resulting surface tension force can result in that ones.

Surface tension can be quantified and is defined as the force per unit length acting along the surface of a liquid. For example, surface tension for water at 20 degrees Celsius is approximately 0.074 N/m. This measurement helps in understanding how different liquids interact with solids.

When you fill a glass with water, you might notice that the water can rise slightly above the rim without spilling. This phenomenon occurs due to surface tension acting at the surface of the water, allowing it to hold its shape temporarily even when the forces exceed the physical boundaries of the glass.

As the temperature is going to increase it so you will have a decrease of the cohesive forces. As the cohesive forces decreases, you can know if the net force is going to decrease. So resulting effect the surface tensions will have a decreasing trend. So we can when you have a interface between the liquid to liquid or the gas to liquid, you will have a the surface will be act like a elastic membranes with a tension forces.

Temperature plays a significant role in determining surface tension. As the temperature increases, the cohesive forces between liquid molecules tend to weaken, leading to a decrease in surface tension. Therefore, warmer liquids usually have lower surface tension compared to when they are colder.

If you've ever boiled water, you'll notice that the steam rises off the water surface. As the water heats up, the increased thermal energy weakens the cohesive forces between water molecules, resulting in lower surface tension — the water behaves differently when hot compared to when it is cold.

If you consider the raindrop if you look at that, if you take that drop and make it two splits. At the interface surface there will be surface tension is working it. The surface tension force is acting between the water and the air.

The interface between liquids and gases affects pressure differences within droplets. When you consider a raindrop, the surface tension creates a pressure difference between the inside of the droplet and the surrounding air. Understanding this mechanism allows us to predict the behavior of droplets under different conditions.

Picture a water droplet on a car windshield. The round shape indicates that the surface tension is holding the droplet together, creating a pressure equilibrium between the inside and outside forces. If you tilt the car, the droplet may slide and re-shape, demonstrating the dynamic nature of these forces.

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