Snowflakes

Aren't snowflakes beautiful?

Did you know that so much snow falls on the earth's surface and almost no two snow crystals are alike?

Yes, indeed, billions, even trillions of snow crystals are formed as it snows, and almost no two are exactly alike.

Just like people's fingerprints, each one has its own distinct character.

Of course, just like people, snow crystals are also categorized into groups.

However, although these groups are formed according to similar snow crystals, even snow crystals within each group differ from each other in terms of size and shape.

Snow crystals are a wonder of nature. 

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How does this happen?

First of all, almost all of them are hexagonal! Like honeycombs, with angular hexagons.

There are snow crystals that are not hexagonal, though. But even these crystals have their beginnings in the hexagonal form.

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What is the secret of the hexagonal shape?

Actually, the formation of the hexagonal shape is due to the formula of the water molecule. 

As we know, a water molecule consists of one oxygen atom and two hydrogen atoms chemically covalently bonded to it.

When these molecules are in liquid state, they slide over each other like grains of sand, but when their temperature drops to zero degrees Celsius, they start to bond to each other in the position where they are side by side. 

This bond is no longer the chemical covalent bond we know.

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But why the hexagonal shape?

To understand this, we first need to look at how temperature affects atoms and molecules.

What is temperature?

Heat energy, so this is a form of energy. 

What happens when an atom receives energy from outside?

In atoms, the orbits where electrons are located are energy levels. 

This orbit is not a circular or elliptical orbit like the planets in the Solar System orbit around the sun. 

The orbits of electrons are more related to the energy levels around the nucleus. 

The latest model of the atom predicts that electrons are in constant motion in bubble-like energy levels connected to the nucleus. 

Normally, the energy that electrons receive from the outside is transmitted by photons and is called radiant energy. 

If the photon reaching the electron has enough energy, the electron jumps to the orbit at the next higher energy level and continues its motion there.

Heat energy, in contrast to radiant energy, is a type of energy that gives vibrations to the entire atom. 

These vibrations affect all the subatomic particles that make up the atom, from electrons to the nucleus. In other words, heat is a type of energy that also vibrates the atomic nucleus.

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As the temperature decreases, atomic vibrations decrease in atoms or molecules in chemical bonds, and this allows the atoms to be closer to each other.

The size of the atoms, the shape of the molecule if they are in the form of a molecule, and many other factors affect this rapprochement.

In a sense, you can imagine the temperature as iron balls vibrating together, both vibrating and bumping into each other and bouncing farther and farther apart.

If the vibration decreases, the iron balls will be able to stay together more easily. If the vibration increases, the balls will start bumping into each other.

In fact, when the vibration increases even more, the bounces will spread much farther and the balls will be completely far away from each other, like the molecules of gaseous substances.

In the liquid state, on the other hand, the level of vibration of the molecules is not such that the molecules are thrown so far away, nor is it such that they can stand close enough side by side as in the solid state. The liquid state is more like a position where the molecules can slide over each other.

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But what happens when the temperature is low enough, and atoms or molecules can be in close proximity to each other? 

Why don't they disintegrate like dust, but become a single whole, like a liquid stone that turns into a solid?

This is when atoms that are normally in chemical covalent bonds, even if they are neutral in terms of their charge position, start to be affected in some way by the electrical charges of the atom next to them. Electron exchanges begin between molecules.

While the single electron of the hydrogen atom in the water molecule normally orbits the oxygen atom to which it is covalently bonded, it also starts to orbit the orbits of the other water molecule that is very close to it. 

In a sense, the atoms start to use the electrons together. 

This results in the solidification of matter and its behavior as a whole.

Under normal conditions, when an electron passes from a molecule whose electron circulation system is in equilibrium to another molecule, an electron from that molecule also passes to this molecule. In this way, electron exchanges start between all molecules.

Thus, although the total electron balance in the system is not disturbed, all atoms begin to be able to stand together in this new order they have established with their electron sharing. They become solid.

We say that water turns into ice at zero degrees. Because zero degrees means that the vibration levels of water molecules decrease enough to allow them to get close enough to each other to exchange electrons, so water turns into a solid at zero degrees.

Since all substances have different molecular arrangements and shapes, the molecular proximity at which they can exchange electrons is different, and therefore the level of heat required for their transformation into a solid is also different.

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In order to disrupt this new electron-sharing system in solid materials, in other words, in order to break that solid material, each material has its own resistance force. 

Therefore, the forces you need to apply from the outside have to be of different magnitudes.

Since I am a civil engineer, let me give an example from construction materials, for example, the force you apply to break a brick is different from the force you apply to break a concrete mass. 

Or since these solid state bonds are much stronger in metals, the breaking forces of iron are quite high.

Of course, the force you apply is also related to how regularly the atoms of that substance come together as it transforms into a solid state and whether cracks form between them. In concrete, we call it setting, and when there are hairline cracks for different reasons at this stage, the strength of the concrete decreases.

These solid state bonds I'm talking about are not chemical covalent bonds, but there are different types of bonds. For metals, for example, the metallic bond is one of them.

There are many types of bonds that hold the atoms of substances together. 

We call the bonds formed by chemical reactions covalent bonds, but there are also ionic bonds, metallic bonds, physical interaction bonds called Van der Waals bonds, and there is another type of bond called hydrogen bonds. 

All these bonds have different levels of bond energies, and these energy levels change depending on the electron sharing of the interacting atoms, the position and energy level of the potential free electron orbital in that orbital.

So it takes a lot more force to break a mass of concrete than to break a brick.

Or you need much more force to break ice.

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We started with snow crystals and wasted so much time with chemistry.

But without knowing these details, unfortunately it is not possible to understand snow crystals and why they have so many shapes.

Yes, I say crystals, because when molecules lose their heat and get close to each other, they take on certain shapes according to their physical structure. 

We call these physical shapes crystals.

When water molecules get close to each other due to their molecular structure, they solidify in a hexagonal form by bonding with hydrogen bonds. 

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What is hydrogen bonding?

Since hydrogen has only one proton in its nucleus, it naturally has only one electron in its orbit. 

But this first level of electron orbit is also the closest to the nucleus and normally there is room for two electrons at this level. Because this level is the closest to the nucleus, it creates a very strong bond between the proton and the electron. 

But as I said, it's also a two-electron level. 

So even though it has only one proton, the hydrogen atom is more inclined to incorporate a second electron than other atoms. 

When a second electron from other atoms enters the vacant orbital, the proton in its nucleus releases its current electron, but this hydrogen bonding is very effective when the water molecule containing hydrogen atoms solidifies into a solid state, and this causes solid water to solidify into a water crystal consisting of six molecules.

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Water molecules also have a property that may be the reason why life began in nature.

This hexagonal molecular arrangement, with a gap in the middle, causes water to increase in volume when it turns into ice, unlike many other solid substances.

Indeed, almost all substances lose volume when they turn solid. 

Because a drop in temperature means that the molecules move closer together. This means a decrease in volume.

However, in the case of water molecules, even though there is a certain volume decrease at first with the decrease in temperature, the molecular alignment in the crystallization stage causes the volume to increase more than in the liquid position.

This allows the freezing water to shatter huge rocks.

The formation of soil in nature, and therefore the continuation of life, depends on this interesting property of water molecules.

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In the light of this information, let's go back to the snowflakes.

When the temperature drops, the water molecules, which are arranged in a hexagonal form like a honeycomb, start to grow from the corners of the honeycomb with hydrogen bonds at the corners.

The result is the formation of beautiful hexagonal snowflakes.

The shapes of these very different snowflakes take different shapes depending on the density of the water vapor environment around the hexagonal crystal at that moment, the temperature of the air at that moment and the different layers that the crystal passes into under the influence of gravity.

Even with very sudden temperature changes, the crystal grows in the same way in all directions because the hexagonal honeycomb creates an equal environment on all sides at all times. 

But because the layer through which it passes creates different conditions for each snowflake, this magnificent hexagonal form grows differently for each crystal.

The result is millions of different snowflakes.

For example, a crystal that suddenly passes through a very cold environment causes the top and bottom surfaces of the honeycomb to collect free molecules instead of the corners of the hexagonal starting crystal. That's why very cold temperatures produce needle-like pointed snow crystals.

But milder temperatures are more favorable for the honeycomb to grow from the corners, so flaky snowflakes form in mild weather. And within these flaky snowflakes are magnificent hexagonal snow crystals.

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Scientists who have been studying this subject initially thought that there were more than a hundred types of snow crystals.

In recent years, the classification has been narrowed down to forty-odd levels.

One way or another, snowflakes are the crystals we all love. I don't know about you, but I love snowflakes.

While I was looking out the window, the snowfall increased as the weather softened a little. And what beautiful snowflakes are falling on the window.

Each one shows me the snow crystals inside before melting.

I also put on Nilüfer's song "Snowflakes" from the internet, it's quite romantic here.

/Like birds of prey

Don't go round and round on my head

We're gonna link arms

Don't hit my face with snowflakes/

Stay with science.

Love and regards to everyone from Moscow.