Research
Secrets of the snowflake
2-A class student
MBOU secondary school No. 000
Introduction
1. Selecting a Research Topic
Recently, while walking down the street, I looked at snowflakes. They were translucent and fluffy, graceful and lacy, as if winter were a needlewoman giving us her magical gifts. Smoothly spinning in the air, the snowflakes quietly fell to the ground. Looking at them on my mittens, I noticed that all the snowflakes are different in shape. When I took off the mitten, they quickly melted on my warm palms, turning into droplets of water. I wondered what “secrets” snowflakes kept.
2. Goal of the work: Explore and reveal the secrets of the snowflake.
3. Tasks:
· find out how a snowflake is born, how much it weighs, and what it sounds like.
· determine the beneficial properties of snowflakes;
· find out the “secret” secrets of snowflakes.
4. Object, subject of research:
Object of study: snowflakes.
Subject of study: snow taken in the vicinity of Snezhnogorsk.
5. Hypothesis. I suggest that snowflakes, being a unique natural phenomenon, have interesting properties.
Experiment No. 2.
Purpose: to determine the air temperature on the surface of the snow cover and near the soil.
I first measured the air temperature near the soil with a thermometer. The thermometer dropped to minus 2 degrees Celsius, and on the surface of the snow cover it turned out to be minus 6 degrees.
Conclusion: snowflakes cover the soil with a warm carpet and allow plants to freeze.
Experiment No. 3.
Goal: check when a snowflake can turn into a snowman.
Air temperature. | Property of snow |
|
Morning. Minus 10 degrees | Fluffy, light, crumbles. |
|
Day. The sun is shining. 0 degrees. | The snow has become heavier, but you can already roll a ball. |
Conclusion: As temperatures rise, snow begins to melt. It easily sticks together into lumps. And you can make a snowman out of lumps.
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Experiment No. 4
Goal: check the quality of melted snow and find out whether it can be eaten or not.
For this we needed cardboard funnels, cotton wool, and snow taken for the experiment from the road and our house.
I put this snow in two funnels and began to wait for it to melt.
Then I compared the melted snow. This is what I received:
Indicators | Snow near the road | Snow near the house |
White-gray | ||
Filter dirty | There is dirt | There is dust |
Transparency | ||
You can't eat | You can't eat |
Conclusion: Snow near roads is especially dirty and harmful; it accumulates dirt and gasoline. You can't eat snow near your house either, even though it looks clean. I found particles of dirt and dust in the melted snow.
Snow is very useful for hardening the body and practicing winter sports. Together with my family and friends I love skiing, sledding, and skating. We love to sculpt fairy-tale figures from snow.
I live in the Arctic, in a city with a beautiful snowy name Snezhnogorsk. There is snow in our city from October to the end of May. And in the hills the snow sparkles with its colorful lights until the beginning of June.
Conclusion.
Snowflakes are an amazing, beautiful and mysterious natural phenomenon that are formed from water vapor. Snowflakes have their secrets:
Secret 1. Snowflakes form high in the sky. Moving up and down in the cloud, the snowflake finds itself in conditions with different temperatures and water vapor content. In the air, the shape of snowflakes is constantly changing.
Secret 2. Snowflakes have six sides.
Secret 3. There are no identical snowflakes.
Secret 4. Every snowflake is colorless, like ice. Together they become opaque, do not allow rays to pass through them, but, on the contrary, reflect them into our eyes. And that’s why we see snow as white.
Secret 5. In frosty weather, you can hear the “music” of snow under your feet. These are the rays of snowflakes breaking.
Secret 6. Snowflakes cover the ground and protect plants from freezing.
Secret 7. You can sculpt snow figures from snow.
Secret 8. When snow melts, its volume changes several times.
Secret 9. Snow only seems clean. You can't eat it because it's cold and unclean.
Secret 10. Thanks to snow, people can engage in winter sports.
Bibliography:
1. , A.N. Kazakov “We and the world around us” Textbook for 2nd grade. Publishing house “Educational Literature”.
2. Encyclopedia for younger schoolchildren “What? For what? Why?" Publishing house "Eksmo".
3. I explore the world. Children's encyclopedia. Ecology. Moscow. AST Publishing House, 1999.
4. http://ru. wikipedia. org/wiki
Comments by K.H. n. O. V. Mosina.
Why elementary ice crystals are hexagonal is easy to understand by analyzing the structure of crystalline water - ice.
In a water molecule, two electron pairs form polar covalent bonds between hydrogen and oxygen atoms, and the remaining two electron pairs remain free and are called unshared.
Rice. Water molecule
Because the oxygen atom has more electrons (chemists say that the oxygen atom is more electronegative) than the hydrogen atom, the electrons of the two hydrogen atoms shift towards the more electronegative oxygen atom, causing the two positive charges of the hydrogen atoms to cancel out the equal value of the two atoms hydrogen with a negative charge on the oxygen atom. Therefore, the electron cloud has a non-uniform density. There is a lack of electron density near the hydrogen nuclei, and on the opposite side of the molecule, near the oxygen nucleus, there is an excess of electron density. This results in the water molecule being a small dipole containing positive and negative charges at the poles. It is this structure that determines the polarity of the water molecule. If you connect the epicenters of positive and negative charges with straight lines, you get a three-dimensional geometric figure - a regular tetrahedron.
The unit cell of water is tetrahedra containing five H2O molecules connected to each other by hydrogen bonds. Moreover, each of the water molecules in simple tetrahedra retains the ability to form hydrogen bonds. Due to their simple tetrahedrons, they can be united by vertices, edges or faces, forming a variety of spatial structures.
Rice. In the crystal structure of ice, each water molecule participates in 4 hydrogen bonds, forming a tetrahedron
Thus, the structure of water is associated with the so-called Platonic solids (tetrahedron, dodecahedron), the shape of which is related to the golden ratio. The water molecule also has the shape of a Platonic solid (tetrahedron).
And of all the variety of structures in nature, the basic one is the hexagonal (six-sided) structure, when six water molecules (tetrahedra) are combined into a ring. This type of structure is typical for ice, snow and melt water.
A snowflake is a complex symmetrical structure consisting of ice crystals collected together. There are many options for “assembly” - so far it has not been possible to find two identical ones among the snowflakes. Research conducted in Libbrecht's laboratory confirms this fact - crystal structures can be grown artificially or observed in nature. There is even a classification of snowflakes, but, despite the general laws of construction, snowflakes will still be slightly different from each other even in the case of relatively simple structures.
Rice. 1. Crystal structure of ice
So why are snowflakes hexagonal? In the crystal structure of ice, each water molecule participates in 4 hydrogen bonds directed to the vertices of the tetrahedron at strictly defined angles equal to 109°28" (while in ice structures I, Ic, VII And VIII this tetrahedron is correct). In the center of this tetrahedron there is an oxygen atom, at two vertices there is a hydrogen atom, the electrons of which are involved in the formation of a covalent bond with oxygen. The two remaining vertices are occupied by pairs of oxygen valence electrons, which do not participate in the formation of intramolecular bonds. Now it becomes clear why the ice crystal is hexagonal.
The main feature that determines the shape of a crystal is the connection between water molecules, similar to the connection of links in a chain. In addition, due to the different ratios of heat and moisture, the crystals, which in principle should be the same, take on different shapes. Colliding with supercooled small droplets on its way, the snowflake simplifies its shape while maintaining symmetry.
But why do elongated snowflakes sometimes form? A snowflake is a single crystal of ice, an analogue of a hexagonal crystal, but one that grew quickly under non-equilibrium conditions. Under some conditions, ice hexagons grow intensively along their axis, and then elongated snowflakes are formed - columnar snowflakes, needle snowflakes. Under other conditions, hexagons grow predominantly in directions perpendicular to their axis, and then snowflakes are formed in the form of hexagonal plates or hexagonal stars.
For more information about snowflakes and the processes of their formation, read the article by Sergei Apresov “White Magic”:
K. x. n. O. V. Mosin
WHY ARE SNOWFLAKES HEXAGONAL?
To understand why snowflakes look so beautiful, we need to consider the life history of one snow crystal.
Ice snowflakes in the cloud form at -15 degrees due to the transition of water vapor to a solid state. The basis for the formation of snowflakes are small dust particles or microscopic pieces of ice, which serve as a nucleus for the condensation of water molecules on them. The crystallization nucleus is where the formation of snowflakes begins.
More and more water molecules attach to the growing snowflake in certain places, giving it a distinct hexagonal shape. The key to the structure of solid water lies in the structure of its molecule, which can be simply imagined as a tetrahedron - a pyramid with a triangular base in which angles of only 60° and 120° are possible. In the center there is oxygen, in two vertices there is hydrogen, or more precisely, a proton, the electrons of which are involved in the formation of a covalent bond with oxygen. The two remaining vertices are occupied by pairs of oxygen valence electrons, which do not participate in the formation of intramolecular bonds, which is why they are called lone.
A snowflake is a single crystal of ice, a variation on the theme of a hexagonal crystal, but one that grew quickly under non-equilibrium conditions. Under some conditions, ice hexagons grow intensively along their axis, and then elongated snowflakes are formed - columnar snowflakes, needle snowflakes. Under other conditions, hexagons grow predominantly in directions perpendicular to their axis, and then snowflakes are formed in the form of hexagonal plates or hexagonal stars.
A drop of water can freeze to a falling snowflake, resulting in the formation of snowflakes of irregular shape. The common belief that snowflakes necessarily have the shape of hexagonal stars is erroneous. The shapes of snowflakes turn out to be very diverse.
Astronomer Johannes Kepler wrote a whole treatise “On Hexagonal Snowflakes” in 1611. In 1665, Robert Hooke used a microscope to see and publish many drawings of snowflakes of various shapes. The first successful photograph of a snowflake under a microscope was taken in 1885 by American farmer Wilson Bentley. The most famous followers of Bentley's cause are Ukihiro Nakaya and the American physicist Kenneth Libbrecht. Nakaya was the first to suggest that the size and shape of snowflakes depend on air temperature and moisture content, and brilliantly confirmed this hypothesis experimentally by growing ice crystals of different shapes in the laboratory. And Libbrecht, at Caltech, is still busy growing snowflakes all day long. The scientist, together with photographer Patricia Rasmussen, are planning to publish a book that will include the most photogenic snowflakes, some of which can already be seen on his website SnowCrystals.com.
There is another mystery inherent in the structure of a snowflake. In it, order and chaos coexist together. Depending on the production conditions, the solid must be either in a crystalline (when the atoms are ordered) or in an amorphous (when the atoms form a random network) state. Snowflakes have a hexagonal lattice, in which oxygen atoms are arranged in an orderly manner, forming regular hexagons, and hydrogen atoms are arranged randomly. However, the connection between the structure of the crystal lattice and the shape of a snowflake, which is ten million times larger than a water molecule, is not obvious: if water molecules were attached to the crystal in a random order, the shape of the snowflake would be irregular. It's all about the orientation of the molecules in the lattice and the arrangement of free hydrogen bonds, which contributes to the formation of smooth edges.
Water vapor molecules are more likely to fill voids rather than adhere to smooth edges because the voids contain more free hydrogen bonds. As a result, snowflakes take the shape of regular hexagonal prisms with smooth edges. Such prisms fall from the sky, with relatively low air humidity in a wide variety of temperature conditions.
Sooner or later, irregularities appear on the edges. Each tubercle attracts additional molecules and begins to grow. A snowflake travels through the air for a long time, and the chances of meeting new water molecules near the protruding tubercle are slightly higher than at the faces. This is how rays grow on a snowflake very quickly. One thick ray grows from each face, since molecules do not tolerate emptiness. Branches grow from the tubercles formed on this ray. During the journey of a tiny snowflake, all its faces are in the same conditions, which serves as a prerequisite for the growth of identical rays on all six faces. Under ideal laboratory conditions, all six directions of a snowflake grow symmetrically and with similar configurations. In the atmosphere, most snowflakes are irregular crystals; only some of the six branches can be symmetrical.
Nowadays, the study of snowflakes has become a science. Back in 1555, the Swiss explorer Mangus made sketches of the shapes of snowflakes. In 1955, Russian scientist A. Zamorsky divided snowflakes into 9 classes and 48 species. These are plates, needles, stars, hedgehogs, columns, fluffs, cufflinks, prisms, group ones. The International Commission on Snow and Ice adopted a fairly simple classification of ice crystals in 1951: platelets, star-shaped crystals, columns or columns, needles, spatial dendrites, tipped columns and irregular shapes. And three more types of icy precipitation: fine snow pellets, ice pellets and hail.
In 1932, nuclear physicist Ukihiro Nakaya, a professor at Hokkaido University, began growing artificial snow crystals, which made it possible to compile the first classification of snowflakes and identify the dependence of the size and shape of these formations on temperature and air humidity. In the city of Kaga, located on the western coast of the island of Honshu, there is a Museum of Snow and Ice founded by Ukihiro Nakaya, which now bears his name, symbolically built in the form of three hexagons. The museum houses a machine for making snowflakes. Nakaya identified 41 individual morphological types among snowflakes, and meteorologists S. Magano and Xu Li in 1966 described 80 types of crystals.
Under certain conditions, in the absence of wind, falling snowflakes can adhere to each other, forming huge snow flakes. In the spring of 1944, flakes measuring up to 10 centimeters in diameter, similar to whirling saucers, fell in Moscow. And in Siberia, snow flakes with a diameter of up to 30 centimeters were observed. The largest snowflake was recorded in 1887 in Montana, America. Its diameter was 38 cm, and its thickness was 20 cm. This phenomenon requires complete calmness, because the longer the snowflakes travel, the more they collide and adhere to each other. Therefore, at low temperatures and strong winds, snowflakes collide in the air, crumble and fall to the ground in the form of fragments - “diamond dust”. The likelihood of seeing large snowflakes increases significantly near bodies of water: evaporation from lakes and reservoirs is an excellent building material.
The ice that forms a snowflake is transparent, but when there are a lot of them, sunlight, reflected and scattered on numerous faces, gives us the impression of a white opaque mass - we call it snow. The snowflake is white because water absorbs the red and infrared parts of the light spectrum very well. Frozen water largely retains the properties of liquid water. Sunlight, passing through a layer of snow or ice, loses red and yellow rays, which are scattered and absorbed in it, and the light that passes through is bluish-green, blue or bright blue - depending on how thick the layer was in the path of the light .
DATA about snowflakes
Snowflakes form a snow cover that reflects up to 90% of sunlight into space.
In one cubic meter of snow there are 350 million snowflakes, and throughout the entire Earth - 10 to the 24th power.
The weight of the snowflake itself is only about a milligram, rarely 2…3. Nevertheless, by the end of winter, the mass of snow cover in the northern hemisphere of the planet reaches 13,500 billion tons.
Snow is not only white. In arctic and mountainous regions, pink or even red snow is common. This is due to algae living between the crystals. But there are cases when snow fell from the sky already colored. So, on Christmas Day 1969, black snow fell in Sweden. Most likely, this is soot and industrial pollution absorbed from the atmosphere. In 1955, phosphorescent green snow fell near Dana, California, killing several people and causing severe harm to those who tried it on their tongues. There were different versions of this phenomenon, even atomic tests in Nevada. However, they were all rejected and the origin of green snow remained a mystery.
Kenneth Libbrecht: snow under a microscopeThe popularity of the American Kenneth Libbrecht all over the world was brought by winter, or rather by such a necessary attribute as snow. The epigraph to his work is the words of Henry David Thoreau: “The air in which they arise is filled with creative genius. It’s unlikely that I would have admired it more, even if real stars had fallen on my coat.” Can you guess what we're talking about? Right. About snowflakes! Kenneth Libbrecht was born in 1958 in Fargo, North Dakota. And he is not a photographer, as it might seem at first glance, but a scientist. Kenneth is a professor of physics at the California Institute of Technology. At the beginning of his career, our hero was interested in astronomy, but his latest research is devoted to studying the qualities of ice crystals, and especially the structure of snowflakes. It was as a complement to Kenneth's professional research that several popular books were published, illustrated with photographs of snowflakes of a wide variety of shapes and sizes. Most snowflakes have six-sided symmetry, although there are specimens with three and twelve sides. But it is impossible to see a crystal with four, five or eight sides, Kenneth assures us. The most ideally shaped snowflakes, according to the author, can be found when there is light snowfall and a light wind blowing, and the weather is especially cold. The popularity of Kenneth's work is further demonstrated by the fact that four of his photographs were selected by the United States Postal Service as designs for the 2006 Winter Holiday stamps. The total circulation of stamps was about three billion copies. “Every snowfall is an adventure for a photographer because they all bring different crystals,” says Kenneth Libbrecht. “And it’s true – no two snowflakes are alike.” Well, if this is so, then we can confidently say two things: the author is provided with work for life, and his creations can be viewed endlessly. Photographer Yaroslav Gnatyuk - HIV virus model - visualscience.ru/illustrations/modelling/gripp-H1N1-interactive/ |
Winter. It's not very cold outside and it's snowing. Place your sleeve under the falling flakes - how many snowflakes are stuck together with their prickly edges! And each of them can be looked at for a long time - its unique pattern is so beautiful and perfect. How are they formed?
Gift from heaven
Each time a close examination of an ordinary snowflake causes surprise and delight. While exploring this weather phenomenon about 400 years ago, the German astronomer Johannes Kepler was the first to scientifically describe what snowflakes are in his treatise “New Year's Gift. About hexagonal snowflakes." Subsequently, many researchers from different countries studied this natural phenomenon. More than three hundred years ago, snow flakes were first examined using a microscope and sketched. Photographers also contributed to the knowledge of this winter miracle. The original method of photographing snowflakes was invented by Russian photographer A. A. Sigson at the end of the 19th century.
He captured about 200 different shapes of snowflakes on film. However, the American Wilson Bentley managed to take the most photographs of icy stars - about 5000! His collection of photographs of snowflakes is still the most famous.
Solid water
How are such perfect lines formed in nature, as if drawn from a drawing? The Earth's atmosphere contains a lot of water due to constant evaporation. From warmer layers of air it moves to cold ones, with sub-zero temperatures, and freezes there. It turns out that the answer to the question “what are snowflakes” is very simple: they are ice crystals. They form high in the sky, where it is very cold, from frozen water vapor and slowly fall down. On their way to Earth, complex metamorphoses continuously occur with them.
What is the secret of the form?
Why are ice crystals so diverse? What is a snowflake made of and how does it get its shape? First, very tiny crystals form inside the water cloud. Oddly enough, in the center of each of them there is usually a tiny particle of dust, blown into the sky by the wind. The initial crystal size is approximately 0.1 mm. How do snowflakes appear from such ice floes? The cloud is constantly moving, and the temperature inside it changes. As a result of this, transformations occur in the crystal - it continuously attracts to itself the same frozen tiny particles of water, which “stick” to it.
That is why the shape of snowflakes is unique. It changes with the ambient temperature. From experience we know that most often snow flakes, consisting of many large, perfectly even sparkling snowflakes, fall from the sky at sub-zero temperatures from -10 to 0 o C. This is explained by the fact that air humidity increases with rising temperatures, and from this more and more water crystals floating there collide with each other and connect. Sometimes there are snowflakes of simply gigantic size. The largest of them was about 38 cm in diameter.
The solution is in the molecular formula
A simple scientific explanation can always be found for any natural phenomenon. Let's remember our chemistry lessons to understand what a snowflake is. The formula of water is H 2 O, its molecule consists of two hydrogen atoms and one oxygen atom. Therefore, in a solid state, water forms crystals with three or six faces. This is how six-pointed snow flowers with an intricate unique pattern are obtained.
New connections arise at the nodes of the hexagonal crystal lattice, and it becomes more complex and grows in these directions. Ice rays with an identical pattern grow on each face, since the growth of crystals on one snowflake occurs synchronously under the same conditions in a single period of time. The angle between them can be 600 or 1200 degrees. None of the snowflakes repeats the other - this is the main mystery and attractiveness of this icy beauty.
Light as snow
As we know, the snow is very light. The thing is that when snow crystals of bizarre shape are formed, multiple air voids are formed inside them. What are snowflakes, or rather, their crystals? This is a kind of openwork mesh, 95% filled with air. Snowflakes are the lightest and most voluminous type of snow crystals. They usually weigh about a milligram. Therefore, they are very light and quietly float in the atmosphere, gradually descending.
The trajectory and speed of each ice crystal are individual. Due to this, they move in air masses with different temperatures and water vapor content and form unique patterns containing up to 200 individual crystals. Snowflakes are the lightest and most voluminous variety.
Snow also comes in the form of small, prickly snow pellets - there the crystals are compressed more tightly. One cubic meter of snow contains more than 300 million snowflakes.
As we know, water has no color. Why then are snowflakes and snow generally white? Their edges reflect sunlight, which, as we know, consists of a color spectrum into which white color breaks up. This can explain the “amazing” snowfalls of different colors - between the water crystals, depending on various reasons, various substances can freeze - from exotic red algae to ordinary coal dust.
Snowflakes in a scientific way
It turns out that scientists are studying snowflakes and even distinguish several varieties based on the method of crystal formation. They came up with various classifications for them, in which the number of varieties reaches 80. The simplest definition system was proposed in 1951 by the Snow and Ice Commission of the International Association of Scientific Hydrology.
It includes seven types of crystals:
- needle-shaped - elongated and sharp at the ends, really similar to needles;
- star-shaped - classic hexagonal snowflakes that have long sharp rays with an intricate pattern;
- plates - resemble flat hexagons;
- columns - thin tubes filled with air;
- voluminous dendrites - several snowflakes that have thawed and frozen again;
- crowned columns - crystals similar to plates, only three-dimensional;
- irregular crystals - with broken rays.
In winter, snowflakes do not always look like a perfect hexagonal flower. As we wrote above, this depends on humidity and air temperature.
Miracle from cold lands
As we know, the weather depends on the time of year and the degree of distance of the area from the cold poles. We can observe falling snowflakes in winter only in certain temperature zones of the planet.
When the air temperature near the earth's surface is above zero degrees, the snow simply does not reach it, melts and turns into rain. Therefore, residents of many countries located in hot latitudes are deprived of the opportunity to observe this natural phenomenon in reality - snowfall. They only saw him in pictures. And vice versa, there are places on the planet where eternal winter reigns.
