Surely you have ever stared at the rain, puzzled and amazed by the way the raindrops fall on it. Drops that always resemble a circular or oval shape and that, in person, you see them fall as if they were needles. What mysteries are behind the formation of drops of water? What is hidden under the surface of tiny water droplets and why do water droplets form?
If you want to decipher all these enigmas and doubts, keep reading 
A drop of water
Water is the most abundant element on Earth's surface. Thanks to water, life as we know it can exist. Without it, there would be no rivers, lakes, seas, or oceans. Furthermore, we ourselves could not live, since we are made up of approximately 70% water.
Water can be found in three states: solid (as ice), liquid (water), and gas (water vapor). Its change of state depends entirely on temperature and pressure. When heat is applied to ice, its energy increases the vibrations of the water molecules inside, and it begins to melt. If this heat continues, the particles will separate so much that they will become a gas. Water vapor is nothing more than tiny droplets of water. But…
Why are drops of water formed?
When we point to the molecules that make up water, we picture them as circular, like balls held together by vibrating and rotating. If this were the case, why doesn't water spread out to the thickness of a single molecule when it's spilled? This happens because of something called surface tension. Thanks to the surface tension between molecules, we can float a needle on top of a glass, or water striders can walk on water.
To understand this, you need to know what is going on inside the liquid. Water is made up of molecules and these, in turn, are atoms. Each atom has positive charges (protons) and negative charges (electrons) and they have one or the other form, depending on the type of molecule they are forming. Sometimes the electron shell attracts each other more, and sometimes the protons and electrons. Therefore, we know that there are forces of attraction and repulsion.
When we observe a molecule inside a liquid, we can see how it is completely surrounded by other molecules, and how all the intermolecular forces cancel each other out. If one molecule pulls to the left, another will pull to the right with the same intensity, so they cancel each other out. This makes the molecules have less energy and be more stable . The state that requires the least energy to maintain is always sought; what is hot cools down, what is high falls, and so on.
Things get complicated when we look at the molecules in the water's surface layer. These molecules aren't completely surrounded by other molecules. They only experience forces from one side, but not the other. To overcome this problem, the molecules rearrange themselves, trying to find a shape that minimizes the surface area they occupy. For a given volume, the geometric shape with the smallest surface area is the sphere.
For all these reasons, water droplets form when water is poured and take on a circular or spherical shape. This is also why objects with little mass and that are denser than water (such as water striders) can float, since the water's surface tends not to break to allow a foreign object to enter. To learn more about the behavior of water, you can consult the section on water vapor or continue reading about the shape of raindrops.
The surface tension in water is higher than in other liquids since the geometry of its molecules is angular and causes more forces to exist.
Why are raindrops shaped like a teardrop?
Once the reason why drops of water are formed, it is time to explain why these drops take the shape of a tear when they fall from the sky during the rain.
Raindrops are usually depicted as teardrop-shaped. However, unless they fall on a window, they don't have a teardrop shape. Small raindrops have a radius of less than one millimeter and are spherical. Larger raindrops take on a hamburger bun shape when their radius exceeds 4,5 mm. When this happens, the drops become distorted, forming a parachute with a tube of water around the base, and then disperse into smaller droplets.
This change in the shape of water droplets is due to the interaction of two forces acting simultaneously. The first is the surface tension mentioned earlier, and the second is air pressure , which pushes the base of the droplet upward as it falls. When the water droplet is smaller, surface tension exerts a greater force than air pressure, so the droplet takes on a spherical shape. As the size of the water droplet increases, its falling speed also increases, as does the force of air pressure acting on it. This causes the droplet to flatten and develop a depression within it.
When the radius of the drop exceeds 4 mm, the depression in the center of the drop increases in such a way that it forms a pocket with a ring of water on top , and from this large drop several smaller ones are formed.
With this information you will be able to know a little more about the drops of water and why they have that shape when they are in different places. Now you can look through the window with a greater knowledge about the element that gives us life.
