Why does snow crunch underfoot when it's cold? What is snow and why is it white? What determines the shape of a snow crystal

18.10.2019

Snow creaks. In very frosty weather, its creak can be heard for several tens of meters. What caused this phenomenon? Why do sounds get louder and weaker as the temperature changes?

It turns out that the creak is a consequence special structure snow, and when the temperature rises / falls, this structure changes and sounds are formed already different.

Snowflakes: education and structure

Snow is “composed” of individual snowflakes - crystalline formations consisting of frozen water (about 5%) and air (about 95%). The composition determines their fragility, lightness and extremely low strength, and the predominant proportion of air -.

Scientists have studied in detail the process of formation of snowflakes. Water that evaporates from the surface of the Earth rises in the form of vapor into the atmosphere, where it cools and concentrates into droplets, forming rain clouds.

With significant cooling, microscopic droplets, in contact with dust particles, freeze, forming six-pointed crystals.

Dust, as well as smoke particles, even insects become the core of crystallization. Snow researcher A. D. Zamorsky talks about a snowflake, in the core of which was small midge- a crystal has grown around the frozen insect.

The six-pointedness of the main crystal of a snowflake is due to the peculiarity of the water molecule, due to which the angle between the rays can be only 120 ° or 60 °. But each of us, looking at a snowflake, saw how much more complex and beautiful its pattern is than an ordinary hexagon. The patterning is caused by the growth of other crystals on the main beams, with their own angles.

There are also snowflakes of irregular shape. It was formed as a result of the constant movement of snow in the air layers, where it either thaws or crystallizes again, building up new rays on the deformed parts.

In the middle of the twentieth century, the Snow and Ice Commission, which is a department International Association scientific hydrology, adopted as the fundamental International Snow Classification. Pundits have divided all the snowflakes into ten large groups. Each could now be defined in one of the classes:

- stars, or dendrites;

- spatial (complex) dendrites;

- irregular crystals;

- plates;

- columns;

- crowned columns;

- hail;

- grains;

— freezing rain.

In each class, subspecies are distinguished, for example, broken crystals, complex particles from many crystals, particles in frost and many others.

The disadvantage of the classification is that it does not take into account the shape of the structure of snow grains in the snow cover, which is even more complex and diverse.

What determines the shape of a snow crystal?

Professor-researcher U. Nakaya, an employee of the University of Hokkaido, has been dealing with this issue all his life. At the beginning of the 20th century, in 1936, in his tiny laboratory, he was the first on earth to obtain an artificial snowflake in terms of appearance.

In memory of the "master of snow" by the Japanese on the territory former laboratory a park was laid out in which the monument was erected.

The professor found out that the shape of a snow crystal depends on the moisture content in the air and its temperature. So, the most beautiful snowflakes - stars - are formed in a narrow range from -14°С to -17°С.

All data were obtained and repeatedly confirmed by U. Nakaya experimentally. The process has not received a theoretical justification and interpretation and is waiting for its discovery.

Causes of snow squeak (crunch)

It is easy to guess from the previous explanations that the creak of snow is crystals breaking when pressed. When we step on snowflakes, their extremely fragile rays break.

An additional creak and crunch is created by the friction of the crystals against each other. Snow creaks especially loudly in frost - 1000–1600 Hz, when the crystals acquire increased (for them) hardness and brittleness and are deprived of the water lubricant permanently present on their surface - evaporation.

As the temperature rises, the snow melts, evaporation increases, water softens the friction of the crystals, and the snowflakes themselves become less fragile - “soft”. When pressed, they break and crumble. The sound from the destruction of "soft" crystals is in the range of 250-400 Hz. When the temperature rises to -6 ° C and above, the crunch and creak noticeably weaken to complete disappearance.

If the snow is caked or the snowflakes are melted into a crust, the bonds between them become much stronger, and they are able to crunch even at 0 ° C. True, it looks a little like a creak, rather, a rustle or a specific noise.

Children love to ask different questions, which can be difficult to answer. We have already found out why the fallen snow white color. At first glance, the answer to this question is very simple. But actually it is not. This time we will talk about snow again, we will figure out why it makes a characteristic sound, crunch or creak at sub-zero temperatures.

To answer this question, why the snow crunches underfoot, you first need to understand what it is all about - snow. High above the ground, among the clouds, water freezes and turns into small crystals. These crystals are called snowflakes. They always take the form of a hexagon.

After freezing, they begin their journey to the ground, and in the process, more and more crystals freeze to each of the six corners. This happens randomly for some time, so the probability of finding two identical snowflakes is extremely small. Each snowflake has its own unique size and shape.

Why do snowflakes crunch when stepped on

It's very simple - when the snow is pressed, a lot of crystals break against each other. It is especially interesting that the loudness of the crunch depends on the air temperature - the colder it is, the louder the snowflakes break.

This is because as the temperature drops, the crystals become harder and harder, and they break more easily. There is another hypothesis - the crunch occurs because the snowflakes rub against each other.

But if we pick up and break one snowflake, we will not hear any sound. He is very quiet, and no one in the world can distinguish him. The crunch effect occurs only when a huge number of ice crystals break at once. It is because so many snowflakes are breaking at the same time that we hear this sound.

If the temperature rises, the crystals begin to turn into water, it becomes more difficult to break them, and the sound disappears.

Snow is a sign real winter. It is formed when small raindrops freeze. Fluffy White snow- a real miracle. Children make snowmen out of it, play snowballs with them, and northern peoples build their houses out of snow. A thick layer of snow warms the earth. It does not allow frosty air to reach it, and maintains a positive temperature in the depths of the soil.

What is snow and how is it formed?

If to speak scientific language then snow is a view precipitation. This means that snow falls from the sky in the form of frozen rain. Snow is cold, white and fluffy. It consists of individual snowflakes that look like six-pointed stars. I wonder how snow is formed?

The first condition for the appearance of snow is cold. The temperature at which water turns into ice is 0ºC. When it gets cold outside, the water in puddles and lakes becomes covered with ice (freezes). In the sky at this time freeze rain clouds. Raindrops turn into snow.

The second way snow is formed is scientifically called evaporation. Hear how it goes. If you wash clothes and hang them outside in winter, the wet sheet will first freeze and become hard. After a few days, the sheet will turn into a soft, dry cloth. What happened? First, the water in the sheet turned to ice. It happened pretty quickly. Then the ice began to evaporate: small microscopic pieces of ice broke off the sheet and rose into the sky. These ice floes were so small that, looking at the drying sheet, we did not notice their flight.

Why is it snowing?

Many small ice floes are found in the heavenly heights. There they gather in a snow cloud. There are so many snowflakes in a cloud that they join together in several pieces. A few small ice stars form a large snowflake, which becomes too heavy and falls down. This is how the snow starts.

In order to form a large snow cloud, one wet sheet is not enough. Many tiny pieces of ice rise into the sky from a frozen lake, puddle or river. There they gather in large snow clouds.

The wind can carry such a cloud far. For example, where there is no frost. Thanks to the wind, snow can fall even in places where lakes and rivers have not yet frozen.

How are snowflakes formed?

Have you ever seen a snowflake under a microscope? It looks like a six pointed star. Each end of the asterisk consists of a white branch on which small white twigs grow.

These branches are scientifically called crystals. They intersect in the middle of the snow star. Each snowflake begins to grow from the center - from the place where the snow branches intersect. The growth of a snowflake is similar to the growth of a tree: six trunks grow from the center, on each of which branches begin to grow. Stars can have different branches (long or short, thick or thin), but always only 6 large branches grow in a snow star.

When water in a river or puddle freezes, ice is formed. The stars in the ice are located close to each other. When the fog or cloud freezes, the stars are located at some distance from each other. If there are too many stars, they are connected in several pieces and fall down. So the snow falls out of the clouds and covers the roads, houses and fields. Falling snowflakes adults call snowfall.

Why does the snow creak underfoot?

If there is a slight frost on the street (-2 or -3 ºС), then there is a lot of water in the fallen snow. They say about such snow that it is “wet”. It is easy to make snowballs out of wet snow and snowman, build "fortresses".

When the frost gets stronger (the air temperature drops to -5 or -10 ºC), the snow freezes harder and becomes dry. It is impossible to make a snowman out of dry snow, but it creaks loudly underfoot. Why does dry snow creak?

Each snowflake is like a small star. If we step on the snow, the branches in the icy snowflakes break. So when breaking many snowflakes, a crunch and creak is formed.

Snow creaks with any pressure:

if it was stepped on;
went on skis;
rode on sleds.

Snow stops creaking only when it becomes almost warm (air temperature approaches 0ºC). Or when he was heavily rolled (this happens on the hills, where the snow rolls and turns into ice).

When the snow creaks very loudly?

Snow can squeak louder or quieter. When does the crunch of snow get very loud?

This happens in extreme cold. For example, on far north at -50ºC the crunch of the snow becomes so loud that it can be heard in the next street.

With warming, when the air temperature approaches 0ºC, the crunch disappears completely. Snowflakes become soft, drops of water appear on their icy branches, which prevents the icy stars from creaking.

Scientists conduct curious experiments with frozen water. It turns out that water hears us and reacts differently to gentle and rude words. That's what the next video is about.

How is snow born?

Snow is a lot of beautiful sparkling snowflakes that fall from a height to the ground.

In winter, the wind drives clouds to our land from the side of warm oceans and seas. Above the ground, when clouds cool, small crystals form in them, and new vapor particles settle and cool on their surface, which turn into new ice crystals. This hexagonal crystal grows, develops all the time and, finally, becomes an amazingly beautiful snowflake, which we admire during a snowfall.

Why is snow white?

If we look at the snowflake, this little star through which Sunbeam, then we will notice that it is colorless. Then why is snow white if it consists of snowflakes? Because when it snows, snowflakes fall randomly on top of each other, lie in a homogeneous mass and become opaque, since they cannot completely let the sunbeam through them. A sunbeam is white, so we see the snow as dazzling white.

Why does the snow creak underfoot in cold weather?

The fact is that each snowflake is a small crystal. When you step on the snow, the mass of these crystals shrinks, rubs against each other and breaks. When the frost is small, then when stepping on the snow, the snowflakes-crystals shrink, but at the same time, some of the snowflakes melt and turn into water. Water becomes a kind of lubricant for the rest of the crystals, and they do not creak. But in hard frost there is no melting of snowflakes and the creak of snow is heard - the noise from crushed snow crystals. Moreover, the stronger the frost, the higher the sound.

(From "The First Encyclopedia of Little Whys")