Why are water droplets spherical in shape ? | Science In Nature 😇

Why are water droplets spherical in shape?

        You probably might have enjoyed dancing during the rain & even after the rain stopped, you would enjoy the cool breeze & amidst that you observe that there are tiny water droplets present on leaves in your garden and if you were to go nearer to a leaf, you would be amazed to see the shape of droplet, its refracting nature. So today we are going to address one of our childhood questions - "Why water droplets are spherical in shape?".

Note: To continue reading this article, you will need a little bit of patience, as we are going to deep dive into it  - from basics to addressing our question. So please take some time to read this article and you will surely enjoy the science behind it.

   

   

        There are number of water molecules inside water. Consider a water molecule inside the water beaker. It is surrounded by many other water molecules around it. This molecule is attracted to each of its neighbouring molecules due to hydrogen bonding.

              Each molecule is attracted to its neighbouring molecules with same amount of force from all sides (because the water molecules want to bunch together), so the net force acting on each molecule inside water is zero which implies that their positions are not going to change with time.

              

              Whereas when we consider a water molecule on surface, it is surrounded by other molecules below and beside it, but there's no water molecule above it. We have air, the atmospheric pressure acting on it and surely the net force acting on it is not equal to zero. This net force is also making the surface molecules to get densely packed  and this makes them have stronger bonds with each other than the molecules in the bulk of the water. 

              This force acting on surface water molecules that is making them have stronger bonds with each other is called Surface Tension.

              Since the surface water molecules form tighter bonds, this allows them to support a certain amount of weight and hence you can see small insects, paper clip are able to float on water.

              Even though a paper clip is more denser than water, it floats, as if the surface molecules form a film on top of water.

                So, now with a clear understanding of  bonding between the molecules, let's address our question.

              

                If we were to take out a water droplet from the beaker, we have air on all sides of the droplet, it is now experiencing a force on all sides and mother nature is asking the water droplet - "hey you better take a good shape now, whenever water was poured into a container, it would take the shape of that container and your shape was not visible to anyone, which shape are you going to choose now in my arena ?".

                Surface tension wants to pull the drop into a ball, while gravity is trying to make it flat. Water molecules on surface are getting pulled inwards. So, the water droplet decides to go with spherical shape for 2 reasons.

               One reason is that, the water droplet wants to take a shape that occupies minimum surface area and among all geometric figures, sphere is the one which occupies minimum surface area.

                Now question arises, what is the problem if it occupies larger area, to address it we will go to our 2nd reason.

              Water droplets decide that it is going to take a shape that possess minimum energy i.e., to be stable in nature. ( Universal law: a body with least energy is said to be stable, while a body with high energy is said to be unstable and every body wants to take the most stable state )

             Sphere is the one that is more stable than others because if you consider a cubical shape, there is wall tension, tension at the corners of the cube, thus making the droplet unstable and same is in other cases too. But sphere removes that (wall) tension on the surface, thus suitably water droplet acquiring the most stable shape in nature - 'Spherical'.

                              

                                                  *****

            

               Hope you have enjoyed reading this article.

          The thing, I want you guys to take away from this blog, is not just the question we addressed today, but to think deeply about simple things. Everything is around you, you need to ask questions - silly or important doesn't matter, but to have the quest in you to answer your 'why' , to question things around you. Don't worry if you don't get answers, because there are some unanswered questions in science too, but don't let the Curiosity die in you!! 

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