Snow melts in the city. Educational event "Why does snow melt faster in the city than outside the city?". The life of a modern person is unthinkable without sophisticated technology. Even in his dwelling, he is surrounded by many devices and devices, most of which are required.
In autumn, children and adults are looking forward to the appearance of snow, which will cover the dirt and slush of the roads with lush snowdrifts. It will be possible to make snowmen all day long and throw snowballs! But spring will come and sooner or later the snow will melt - first in the city, then in the forest. Why does snow melt, and why does it melt unevenly?
What is snow
Snow is a type of precipitation, it is tiny ice crystals that form in the air. Snow is formed when water microdroplets in clouds are attracted to dust particles under the influence of low temperature and freeze into complex symmetrical crystals that fall down and grow due to the fact that moisture continues to condense on them. Have you noticed that snowflakes always have a six-pointed shape? This is due to the fact that the structure of water molecules can only form crystals with beams located at an angle of 60° or 120° to each other. The main crystal in the form of a hexagon is overgrown with small hexagons, and this is how snowflakes are obtained, which we simply call snow.
When the snow starts to melt
From school course In physics, we all know at what temperature snow melts: Snow begins to melt when the air temperature rises above 0 ° C. But in nature, snow can evaporate even at sub-zero temperatures. When water changes from a solid state to a gaseous state, bypassing the liquid stage, this is called sublimation, and the probability of this phenomenon is increased by the action of bright sunlight. Do you know which snow melts faster? Dirty snow melts faster than clean snow. Mud reduces the reflective properties of snow and is heated by the sun's rays, causing the snow to melt. That is why snow melts faster in the city than in the field. The snow melts faster in the field than in the forest. This is due to the fact that in the forest the sun breaks through the crowns of trees less, so the temperature in the forest is lower than in the field and the snow can lie without melting for quite a long time.
Will the salt help melt the snow? In fact, salt does not melt the snow, it breaks the ice. When salt hits the ice, it diffuses, during which the ice first cools and then returns to temperature. environment, but at the same time it turns into salt water. At the same time, outwardly it seems that the salt corrodes the ice. Thus, it turns out that this is just an illusion. As a conclusion, we can say that in nature the snow melts mainly because with the change of seasons there is a change in the temperature regime.
EDUCATIONAL EVENT
"Solution of the project problem" for students in grades 3-4
Stage 1. Conversation.
Dear guys, you are invited to a project task-game
“In spring, the snow in the city always melts faster than outside the city. Sasha offered his explanation for this and said that he would need a sheet of black paper, a lamp and a thermometer to check. What assumption did Sasha make and what item required for verification did he forget to name?
By doing it, you will be able to show a lot of what you learned in school. The peculiarity of this task is that it involves a group of students of different ages or different classes. We hope that each of you will find your place in the game, be able to benefit your group. But in order to succeed, in the process of solving this problem, you will have to agree on which part common task It will be up to each of you to come to the aid of each other, to show the ability to prove your point of view and to treat the opinion of your comrades with understanding.
The project task is carried out in two stages. At the first stage, you will prepare for solving problems, and at the second stage you will go to a scientific laboratory and conduct a series of experiments and make a report on how the experiment went, what are its results. .
During the research, you will need to complete a number of tasks. You can move from table to table, and perhaps you will perform some tasks at the same time, distributing them among themselves. It may be more convenient for you to work on the content of the tasks in a different order than they are given. The main thing is to try to complete the work in the allotted time (80 minutes). There will be a break between stages.
We wish you to show your best human qualities as well as knowledge and skills.
There are two photographs on the board: 1 - a road in a field at the edge of a forest and 2 - a road in a city among houses.
Check out these pictures the guys took. Where are the events taking place? If you were an artist, what colors would you need the most? Why?
You are now sitting at the tables and white and black circles are glued to each seat. These are teams of 6 people. Divide into teams by color and come up with a name for your teams.
TASK #1
Here is a map of the Solntsevo Park area. One group will go in the direction indicated on the route sheet and you must plot this route on the map. And the second one lays its route in the direction indicated on the second route sheet. The first and second groups should come to their experimental site and conduct research there that will help solve our problem.
ROUTE SHEET - 1
Exit the school building (marked with an asterisk on the map), turn northeast and walk 350 m, then turn southeast and walk another 350 meters. Then you turn east and walk 250 meters before turning, turn northwest and walk 100 meters. Your test site is in front of you.
ROUTE SHEET -2
Exit the school building, turn southwest and walk 400 meters. Then turn west and walk another 100 meters. Go to the edge of the forest near the pond and in front of you is your experimental site.
ADVICE OF THE EXPERIENCED TRAVELER
The main requirement for the route is its safety. When planning a transition, obstacles should be avoided, since it is precisely when they are overcome that dangers lie in wait for travelers, in addition, overcoming obstacles requires more time than bypassing them along a longer path. When planning a route, you should carefully study the map of the area, as well as the descriptions made by those who have already visited these places. Pay attention to the environment, vegetation, roads, population. Follow the rules traffic.
Stage 2. Equipment for the experiment.
On this table are objects that you can take for the experiment.
Equipment: sheets of black and white paper, table lamp, thermometer, stopwatch, hourglass for 3 minutes
What items did you choose and why would you need them?
1 pair - marks the time,
2 pair - writes down the results,
3 steam - determines the temperature.
Determine the name of the professions that are engaged in this work. (on the board: weather forecasters, accountants, time manager)
Conduct an experiment to answer the problem.
Record the data of your experiments in the observation sheet
observation sheet
Study No.
t° C
at the beginning
Time (minutes)
t° C
at the end
Average temperature (for the purity of the study)
Stage 4 . Presentation of the work of groups 1 and 2.
RESULT: Drawing up a conclusion - an answer to the problem based on the observations of four groups.
SPRING PLANNING
Observations of inanimate nature
Snow observations.
It is interesting to watch the snow melt. Point out to the children that snow melts differently in different places. Where does snow melt first? At tree trunks. Why? Because the tree trunks are dark. Dark colors absorb more sunlight than light colors; Dark-colored objects heat up more than light-colored ones. Dark tree trunks heat up more than white snowdrifts, so the snow around the trees melts faster. Dirty snow also melts faster than clean snow.
You can tell the children that the snow in the forest and in the city also melts in different ways. If the children have a weekend walk in the forest, ask them to pay attention to the snow in the forest. Discuss with the children why snow melts faster in the city than in the forest. Why in the forest, even in late spring, islets of unmelted snow can be found? Because in the city the air temperature, as a rule, is always higher than in the forest (because of the many cars, because a large number people, various heating plants, factories and plants that produce heat). In addition, there are many trees in the forest that provide a dense shade; through the interweaving of branches, it is more difficult for the sun's rays to penetrate to the ground, and therefore the snow under the trees in the forest melts longer.
Snow in the spring becomes porous, it is not at all like winter. You can explain to the children why this happens: from the heat of the sun, the snowflakes on the snow surface melt one after another and turn into water, the water flows down, so depressions form in the snow.
Sun observations.
Why does the sun shine brighter in spring than in winter? This question is often asked by children. You can explain to children that in spring our planet Earth is turned towards the sun, so that more sunlight falls on it than in winter, they give more heat and light. Therefore, in spring, not only is it warmer, but the days are getting longer, and the nights are getting shorter.
Invite the children to touch the sleeves of the dark and light coats and tell which one is warmer: the children can see for themselves that warm light absorbs more sunlight than light. Therefore, the wipers scatter snow and ice along dark paths - this way it melts faster. For the same reason, snow melts fastest around dark tree trunks.
Cloud observations.
In spring, many cumulus clouds form in the sky. You can explain to children the mechanism of their formation: steam rises from melting snow under the influence of sunlight. Above, where the air is much cooler than near the ground, the steam turns into tiny ice crystals, and clouds form from them. The more snow melts, the more such cumulus clouds. They often change shape. Children love to fantasize, looking at the clouds, imagining what they look like.
Observations of melt waters.
In spring, many streams form. Where do they come from - once again ask the children about this. They should already know that snow is frozen water, and when it melts it turns back into water.
Water always flows down from high places. Children will be able to see for themselves when
will make grooves for their boats. Water flows somewhere through a grate laid on the asphalt. Where? You can explain to the children that water flows into special receivers, and from there it enters the city rivers. Wildlife Observations
plant observations
Observation of buds on trees.
In winter and early spring, the buds are small, as if shrinking from the cold. As the sac gets warmer, the buds seem to swell, get bigger, then open up. First, a tiny tip of a green leaf appears. If at this time the kidney is cut and unfolded, then inside it you can see a tiny leaf, as if folded many times. Small young leaves - light green, sticky, sticky, odorous. You can explain to the children that in the spring, when it gets warmer, the earth becomes wet, "everyone is the necessary conditions for plant growth. At the same time, you can repeat with the children what these conditions are:
Sunlight,
Grass observation.
Young grass appears much earlier than the first leaves. It pecks out of the ground on thawed patches even when not all the snow has melted. The first flowers also appear before the leaves open. These are yellow coltsfoot flowers. Among forest flowers, the snowdrop is the first to bloom. The flowers of the lungwort are beautiful, they change their color: at first they are red, then purple, and then they turn blue. On all these plants, the flowers bloom before the leaves.
Bird watching.
Spring is the time for the return of migratory birds. Pay attention to the children that there are no more bullfinches, goldfinches and waxwings, which we often met in winter, at the feeders. Explain that these birds flew north because they like colder climates.
Wintering birds also behave differently. Crows and jackdaws fly in pairs, looking for nesting sites and screaming loudly. Buntings have changed plumage: in winter they looked very much like sparrows with gray feathers, and now their feathers are yellow. Sparrows began to chirp merrily, start fights among themselves, bathe in spring puddles.
Rooks are the first to return from warm lands and immediately set to work, looking for harmful worms and slugs on the thawed patches. They are putting in order their large, sturdy nests of sticks that have been waiting for them all winter.
Then starlings appear. They make nests in birdhouses. It is interesting to watch how they scurry around the opening of the birdhouse, dragging blades of grass and thin twigs there. Sometimes real battles break out in birdhouses between the starlings that have arrived and the sparrows that lived in the birdhouse in the winter, while the starling hosts were absent.
Insect observations.
The first spring butterflies are yellow lemongrass, motley urticaria, dark mourning. They appear as soon as warm weather sets in. These butterflies winter as adults in secluded places, so they appear very first. Those butterflies that winter in the form of pupae will appear much later.
It will be interesting for children to watch how butterflies suck nectar from flowers with their long proboscis, as if through a straw. Butterflies have a very beautiful pattern on their wings - one of the most beautiful that nature has created. But you can’t grab butterflies by the wings, as they are covered with delicate pollen, which is easy to wipe off, and after that the butterfly will not be able to fly.
You can explain to children that butterflies lay eggs, from which caterpillars then hatch. Caterpillars are serious pests of plants - they eat their leaves. Later, the caterpillars entangle themselves with a thread that is isolated from the abdomen and. turn into pupae.
As you watch the beetles, help the children identify what they have in common: 6 legs and 4 wings.
Weather observations.
Continue to teach children to analyze the weather with subsequent marks in the calendar of nature.
To teach children to find a connection between the activity of the sun's rays and the awakening of life in plants, insects, and birds.
Observe with the guys on which side of the veranda, the roof more icicles form, and on which side they melt faster. Analyze which side melts faster snow where the first thawed patches form.
See how long the day has become. This is due to the fact that much more sunlight now hits the Earth than in winter.
Warmer weather in springtime is associated with the same reason. The Earth is so turned towards the Sun, more sunlight falls on it, which means that it receives much more heat in spring than in winter.
In early spring, in the mornings, an ice crust forms on the surface of the snow - crust. Together with the children we will try to answer the question - why does crust appear on the snow? Because the sun warms during the day, and the top layer of snow thaws, and at night it is still frosty, and the melted snow seizes again, freezes - that's the ice crust of the crust.
Children are very interested folk omens. They like to watch and check whether they are really performed, whether it is possible to predict the weather from them, how accurate they are.
Folk omens
Long icicles - for a long spring.
Early arrival of rooks and larks - to a warm spring.
I saw a rook - meet spring.
The swallows have arrived - soon the thunder will rumble.
If a lot of cobwebs fly in the spring, the summer will be hot.
Frogs do not croak until the first thunderstorm.
Late flowering of mountain ash - by a long autumn.
Dictionary activation
Spring vocabulary: thaw, thaw, porous snow, icicle, drops, streams, melted snow, puddles, migratory birds, swollen buds, the vernal equinox, the first flowers and leaves, the awakening of nature.
Together with the children, you can discuss why the spring months in the folk calendar have the following names:
March-morning of the year, drip, protalnik, winter.
April - snowman, aquarius, birch.
May - grass, pollen.
Labor on site
1 Scattering snow, placing it in dark places so that it melts faster. Ice breaking on the veranda. Breaking icicles - explain to the children why this is necessary (so that the fallen icicle does not fall on someone's head).
; We remove last year's yellowed and dry grass so that it is easier for young green sprouts to break through to the sun. Explain to the children why it is impossible to burn last year's grass without first collecting it in a pile. If you set fire to the old grass right where it grew, then the young sprouts also die from the fire.
1 Putting things in order on the site: collecting papers, rubbish brought by the wind, sweeping the veranda.
We collect sand in the sandbox, fill it with new sand, sweep the sides of the sandbox.
: We build dams and canals for makeshift boats.
Role-playing games on a walk
"Young Captains" - a game with homemade and toy boats, ships.
"Building a canal" is a construction game for diverting water from a site into special dams.
"We are shipbuilders" - children learn to make boats from wood chips and paper.
"Spring Journey to the Forest" - children go on an imaginary walk in the forest, guided by the proposed plan or oral description.
Didactic games
“What tree is the leaf from?”, “Migratory birds” - learn to recognize birds by description, “Funny classes” - an exercise in direct and backward counting, “12 months”, “Say the opposite” and “Say it differently” - selection synonyms and antonyms, "Vodyanoy Grandmother" - recognition by touch. :
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When the first snow falls on the ground, and air fluffs cover everything around with a soft snow-white carpet, it seems that there is nothing more weightless than a tiny and small snowflake: it weighs about a milligram and rarely reaches three.
It cannot but surprise how, in a matter of hours, snow-white precipitation manages to cover vast expanses of land with a thick fluffy blanket, which turns out to be so heavy that it directly affects the speed of rotation of our planet. For example, snow in the summer, in August, covers only 8.7% of the entire surface of the Earth, while its weight is 7.4 billion tons, and by the end of winter, before the beginning of spring, its mass doubles.
Snow is a type of atmospheric precipitation, which consists of small ice crystals that fall on the surface of our planet from nimbostratus clouds in the winter season, creating a snow cover that constantly or with minor interruptions covers earth's surface before the arrival of spring.
In the region where the snow has fallen, sub-zero temperatures are established, holding the precipitation in crystalline form.
When temperatures get above zero, the snow melts, and if this process occurs in early spring, this symbolizes the end of the cold period. Ice crystals do not fall everywhere: people living in countries located in equatorial latitudes (in Africa, Australia, South America, South-East Asia, New Zealand and some Central Asian countries).
Snowflakes fly to the ground from nimbostratus clouds after water droplets stick to condensation grains in the clouds, the smallest particles of dust. If the temperature in the upper layers of the atmosphere is between -10°C and -15°C, precipitation is of a mixed type, since it consists of drops and ice crystals (in this case, it will rain with snow or sleet), and if it is below -15° C - will consist only of ice crystals.
When the formed crystals begin to move up and down the cloud, they gradually increase due to the droplets adhering to them (they partially melt and crystallize again). As a result, the ice acquires six-pointed forms of plates or stars, the rays of which are either at an angle of 60 or 120 degrees. After that, new crystals begin to stick to the tops of the rays, to which drops also freeze, as a result of which snowflakes acquire a wide variety of shapes.
The crystals are usually white in color, which they acquire due to the air trapped inside them: after the snow has fallen, Sun rays, bouncing off the air and boundary surfaces of the snowflake, scatter and give it a snow-white appearance. It is worth noting that any snowflake is 95% air, and therefore is characterized by low density and slow falling speed (about 0.9 km / h).
Exist the following types ice precipitation:
- Crystals - their diameter is several millimeters, they are crystals mainly hexagonal in shape;
- Snowflakes - each contains about a hundred crystals fastened together, which in the case of wet precipitation can reach large sizes (up to 10 cm in diameter);
- Frost - extremely cold and small droplets (for example, fog);
- Hail - this snow usually falls in the summer in the form of large hard ice floes and is formed when large drops stick to the crystal.
Types of snow cover
After the snow fell for the first time, comes the climatic winter (the period when the temperature readings are below zero degrees Celsius for five days). If the temperature in the lower atmosphere at the time the snowflakes fall down is very low and a strong wind blows, the crystals will collide with each other, break, crumble and fall to the ground in the form of debris.
But if ice crystals start flying to the ground at a positive temperature, wet snow will fall. It is worth noting that if rain with snow falls from a cloud at a negative temperature, the precipitation, freezing to the road, forms ice.
The snow on the ground is constantly changing. How exactly the snow cover will look depends largely on the winds (they make it uneven), rains (they compact it), thaws, seas (in eastern Russia there is much more ice precipitation than in Western Europe: due to the influence of the Atlantic Ocean, precipitation here falls in the form of rain).
There are the following main types of snow cover:
- Fluffy snow - after the snow has fallen, for some time it is an untouched fluffy cover. This snow in winter is remarkable in that it is a soft pillow, and therefore a fall usually does without injury: loose snow softens the blows. It is very difficult to move along it, it may well hide stones, ice, tree branches under it, and due to the fact that it is impossible to accurately determine the depth of the snow cover, you can suddenly find yourself knee-deep in a snowdrift and even get bogged down.
- Hard - than more people trample down the snow cover, the harder it becomes. If it is not rolled out, then it is much easier to move around.
- Nast - crust solid ice that covers the fluffy snow. It is formed by the sun and the wind: the snow first melts under the sun's rays, after which the cold air freezes it again. Nast can be soft, medium and hard: soft crust will fall through, you can walk on hard crust, and if it turns out to be medium, the pedestrian will either slide or fall through. In the mountains, the weak grip of the crust with snow can cause an avalanche.
- Ice is frozen wet snow that has melted several times and then refrozen. This type of snow cover is the most troublesome, as it is very hard, smooth, slippery, and falling is fraught with serious consequences that can lead to injury or even death. You need to move along it very carefully and, if possible, bypass it.
- Wet snow - after the air temperature is above zero, the ice crystals begin to melt and, filled with water, turn into sleet. As a result, snowflakes begin to stick together and form lumps of ice. Walking on it is quite dangerous: you can get your feet wet, which is fraught with a wide variety of diseases, and if you slip, you can end up in cold water and get wet.
Snowfall time
Since the climate of our planet has been changing tremendously lately, given the unpredictability of the weather, it is quite difficult to predict when the first snow will fall. For example, in Yakutia, in Chukotka, in the Krasnoyarsk Territory, the first snow can be seen already in early October, and snowmelt in some areas occurs only in June.
But in Oymyakon (located south of the Arctic Circle) it is impossible to determine when the first snow will appear. Despite the fact that permanent snow cover here usually appears at the end of September, it can be seen in August (snowmelt in this region occurs in the spring, at the end of May).
As for Europe, the first snow here is already at the end of October or at the beginning of November (the very first snow was recorded in the seventies in Moscow: it fell on September 25). It falls mainly at night, when the air temperature drops and gives the snowflakes the opportunity to reach the ground.
The first snow does not lie for long: during the day, when the temperature rises significantly, and disappears after a few hours. But after a permanent, winter cover is established, the snow lies for a long time, until spring: the snow finally melts in March or even April.
As for the southern hemisphere, the northernmost points where snow has ever fallen are Buenos Aires in South America, the Cape of Good Hope in Africa, and Sydney in Australia. True, it melts quickly and falls infrequently: for example, in July 2007, snow fell in Buenos Aires for the first time in eighty years (the reason is cold air from the Arctic). According to meteorologists, they witnessed a rare event, a similar type of precipitation can be observed here only once every hundred years.
Melting
Snow usually melts in the spring when temperature changes occur: snowmelt occurs at temperatures above zero degrees Celsius. Often there are situations when it melts at sub-zero temperatures (under the influence of sunlight: ice crystals evaporate, bypassing the liquid stage) .
If the snow is dirty, it melts faster (which is why it disappears much faster in the city than in the forest): the sun's rays heat up the mud, causing the snow to melt.
Salt also often helps to disappear the snow cover, while it does not melt the ice, but destroys the crystals, which first cool and then return to ambient temperature in the form of salt water, giving the impression that the snowflakes have melted.
During the snowmelt in spring, the density of the snow cover changes very quickly. First, it is 0.35 g/m3, then 0.45 g/cm3, and at the very end it reaches its critical density of 0.6 g/cm3. T Snow melting ends when wet snow reaches a density of 0.99 g/m3 and turns into water. After that comes the long-awaited spring.
Many people are interested in the question of which snow melts faster: clean or dirty? By the way, there are at least three correct answers to it.
To find the answer to the question of which snow melts faster: clean or dirty, you need to figure out what the subject of discussion is.
Looking at snowflakes, everyone can notice that they consist of small ice needles that stick together into a certain geometrically correct design. Why this happens is a completely different question. Now it is important to understand that snow in its own way chemical composition is water in the solid (frozen) state.
What is the melting point of ice and snow?
There is a second important factor needed when looking for an answer to the question of which snow melts faster: clean or dirty. It's ice and snow.
It is known that water from its solid state to liquid passes at 0 degrees Celsius. It was this point that was taken as a reference when compiling the degree scale, which we all use in practical life. That is, there is no surprising coincidence that ice melts at 0 degrees. It was just convenient for scientists to take this temperature as the main starting point. Just like 100 degrees Celsius is nothing but (transition from liquid to gaseous) the same water. In other words, at this moment steam is formed. In general, this is understandable. After all, water on Earth is the very substance that we can easily observe in all three states.
This is the steam coming from the spout of the kettle, that is, gas. This is directly water, that is, a liquid. This is snow with ice, that is, a solid substance.
Which snow melts faster: clean or dirty?
In this case, two more factors are important. Firstly, where is the snow - in a room isolated from sunlight, or in an open area. Secondly, what is meant by the word "dirty".
If we assume that snow is dirty with earth, sand or other solid substances that cannot dissolve in water, then there will be one answer to the question of which snow melts faster: clean or dirty. But if we talk about a mixture of snow with soluble substances, such as salts, then the answer will be different. This happens because salt solutions have more low point freezing.
That is, snow with an admixture of salt at 0 degrees begins to melt, since at the point of contact there is a mixing of substances - water and salt. A saline solution can be in a solid state at a temperature slightly lower than 0 degrees.
Now everyone understands why the ice on the roads is sprinkled with salt in winter? So that it melts and loses its hardness and, as a result, slipperiness.
Dirty and clean snow in the room
But suppose we are not talking about snow sprinkled with salt, but about the one on which coal or earth was poured. How will this fact affect the rate of its melting?
Speaking from the point of view of the melting point, then no way. The clean and dirty snow brought from the street into the room will turn into water at the same time. Since the transition temperature of both of them from a solid state to a liquid state is the same.
Melting clean and dirty snow on the street
But here the question arises: "Why is snow that interferes with pedestrians sprinkled with sand and earth in spring? And why is dirty snow faster than clean snow?"
The answer is simple: it happens because White color repels the sun's rays, and dark - attracts. Hence, dirty snow heats up faster than white, clean.
It turns out that the janitors also need to be at least a little familiar with the basics of physics and chemistry in order to do their job well. After all, it was only a competent snow cleaner who came up with the idea of \u200b\u200bsprinkling ice paths with salt and sand in order to quickly and easily bring his site into proper order.
