Introduction
Surface tension is an interesting property of all liquids. It is something you can easily observe in our environment when you look at the surface of any liquid like water. While the surface of liquids are expected not to resist any object trying to penetrate it, we observe that there is at least some form of force that repels or holds objects placed on the surface of any liquid. This force that acts like a skin on the surface of liquids is known in science as surface tension.
Today, we make sure of many objects that were made based on the behavior of surface tension. So in this article, we will try to understand what really is surface tension and how it has found application in modern life today.
Surface tension - molecules that bind
So when some water is spilled on glass or other surfaces, they do not spread out. Instead, they form bubbles because the surface acts like an elastic skin that holds the liquid together. That is a great example of surface tension. So, surface tension is a strong cohersive force that exists on the surface of liquids which behaves like a skin, making it harder for any object to enter the liquid.
What surface tension if a force of resistance. It creates a skin for the liquid and protects it from objects that are on the surface. Surface tension can be explained at the molecular level.
Each liquid is made up of molecules interacting with one another. When molecules of a liquid are together, they collide with each other and there is a strong force that binds each molecule to the other. The molecules that the surface exhibit the same forces of cohesion which other molecules have. Thus, the strong forces that binds these molecules at the surface makes them behave like a strong integrated unit. Thus when any object comes to the surface of the liquid, the molecular forces tend to oppose their movement at the surface, acting like a skin.
What really makes surface tension a real force to reckon with is the pressure exerted by molecules below the ones at the surface. Those molecules below pressure the ones at the surface by pulling them down with force. The molecules at the surface thus reacts by attempting to push outside the surface. This creates a strong force at the surface which all objects entering the liquid must break before they enter. This is the reason why surface tension often exists and usually felt on all liquids.
Confirming the strength of surface tension
Surface tension can be observed easily any where liquids can be found. To understand how strong this force could be, notice the following observations:
- Why objects float: Part of the reason why some objects do not sink when placed in liquids is because of surface tension. This is especially true when it comes to objects with light weight - for example plastic and needle. When you place a small piece of plastic in water, it will usually float. This is because the pressure exerted by surface tension on that plastic is strong enough to support its weight. As a result, the object remains at the surface and does not sink. The same is true of needle and other materials with light weight. Surface tension of the fluid is able to support such tiny weights.
The above is one example to illustrate the strength of surface tension in liquids. Here is another example.
- Inserts that do not sink: You will notice that certain tiny inserts appear to walk on water or just perch there without sinking. Some flies and small ants do this. Mosquitoes are a good example. These tiny animals are able to remain on top because the surface tension on that liquid supports their weight. So the next time you observe any animal perch on water and remain there, know that its the work of surface tension.
- Capillarity: Liquids are able to move up narrow tubes partly because of the strong cohesive forces that exist at the surface. Without needing any mechanical energy, water can move up tubes into another container. A person can use the effects of water tension to transfer liquid from one contained to another one using a narrow tube.
When the tube is inserted into the container that has the liquid, a person can simply suck the other end of the tube. The pressure he creates pulls the water because it strongly attracts the forces that exist at the surface or the water. The pressure continues pulling the water once the tube is inserted into the empty container. This is partly because of surface tension at the surface of the liquid.
- Waterproof materials: Materials that are intended to resist water are designed based on the concept of surface tension. For example, umbrellas are made with materials that resist fluids like oil. Thus when its is raining, the water forms droplets when they hit the umbrella and run off. They are able to form those droplets because of the surface tension which acts like a skin on the liquid. Thus, the umbrella remains dry and shelters the owner for rainfall. Umbrellas and similar materials are designed based on the effects of surface tension on liquids.
Finally
Surface tension is a strong force that liquids have and it makes them act like elastics. The next time you notice water running off the surface of some leaves and plants, then you appreciate the role of surface tension in such activities.
Reference
Note: Thumbnail from Pixabay