Introduction
Most of the Earth's surface is covered with water (oceans, seas, lakes, rivers, ice). On Earth, approximately 96.5% of the world's water is in the oceans, 1.7% of the world's reserves are groundwater, another 1.7% is in the glaciers and ice caps of Antarctica and Greenland, a small part is in rivers, lakes and swamps, and 0.001% in clouds, which are formed from particles of ice and liquid water suspended in the air.
Water under normal conditions is in a liquid state, but at a temperature of 0 ° C it turns into a solid state - ice and boils (turns into water vapor) at a temperature of 100 ° C.
The values of 0 °C and 100 °C were chosen to correspond to the melting temperatures of ice and the boiling temperatures of water when creating the “Celsius” temperature scale.
Ice is found in nature in the form of ice itself (continental, floating, underground), as well as in the form of snow, frost, and frost. Under the influence of its own weight, ice acquires plastic properties and fluidity.
Natural ice is usually much purer than water, since when water crystallizes, water molecules are the first to form into the lattice.
The total ice reserves on Earth are about 30 million km³. The main ice reserves are concentrated in the polar caps (mainly in Antarctica, where the thickness of the ice layer reaches 4 km).
In the world's oceans, the water is salty and this prevents the formation of ice, so ice forms only in polar and subpolar latitudes, where winters are long and very cold. Some shallow seas located in the temperate zone freeze over.
In addition, there is evidence of the presence of ice on the planets of the Solar System (for example, on Mars), their satellites, on dwarf planets and in the nuclei of comets.
Research into the properties of water is necessary for humanity.
At the same time, the process of water crystallization can be studied at home, as well as in classes in high school.
The relevance of the work is to be used in physics lessons to familiarize students with the properties of water during crystallization.
The object of study is the crystallization of water.
The subject of the research is to study the properties of water during crystallization.
The purpose of the work is to conduct experiments on water crystallization and prepare proposals for their implementation.
The main task is to study the properties of water during crystallization.
To solve the main problem it is necessary:
- Analyze the basic properties of water.
- Study the significance of water crystallization for the flora and fauna of the Earth.
- Determine the main experiments for conducting the study.
- Conduct experiments and describe the main results.
- Prepare proposals for conducting experiments in high school lessons.
The theoretical significance of the work lies in the systematization of the basic properties of water and the significance of water crystallization for the flora and fauna of the Earth.
The practical significance of the work is the study of the process of water crystallization during experiments, as well as the preparation of proposals for conducting experiments in lessons in high school.
If you want to explore, we work with water
Research work related to water is very common in the scientific world. And how can you miss such an opportunity to discover something new? Several interesting points were revealed not so long ago by British scientists. If we follow the news more carefully, then the chance of seeing something interesting is much greater. So, what was noted by the well-known creators of science? The fact that if you drink a little water before making a difficult decision, it will be much easier. The secret is simple: the liquid, absorbed through the stomach, simplifies the movement of blood through the veins and therefore more brain cells are involved in the work, which significantly improves overall mental work. That is why we can make a decision much faster.
Some people may contrast the effect of water with the effect of alcohol: it also thins the blood. But besides this, it also carries many negative consequences, so on average, the functioning of the brain becomes less successful. There is no doubt: only with the help of water can you really work well with your head.
Preparing for the study
1.1 Analysis of the basic properties of water
Water is one of the most amazing substances on planet Earth. Water can be found almost everywhere under natural conditions, both on the surface of the planet and in its interior in three possible physical states for substances: liquid, solid, gaseous (that is, water, ice, water vapor).
Of course, there are substances that can be obtained in the form of a liquid, solid or gas. However, there is no such chemical substance that occurs naturally in the above three physical states.
Properties of water:
- Water is a substance that has no color, no smell, no taste.
- Water is the only substance known to science on planet Earth that occurs naturally in three physical states: solid, liquid, gas.
- Water is a universal solvent, being able to dissolve more salts as well as other substances than any other substance.
- Water is very difficult to oxidize. Water is quite chemically stable, that is, decomposing it into its component parts or burning it is quite problematic.
- Almost all natural metals can be oxidized by water; especially hard rocks are also destroyed under its influence.
- When water freezes, it has unique expansion properties. Thanks to these properties, ice floats on water, which is in the form of a liquid.
- Water, as a physical substance, is characterized by great affinity with itself. This affinity for water is the greatest among all liquids. As a result, water is placed on the surface in the form of spherical drops, since the sphere has the smallest surface area for a given volume.
- Water freezes not at the temperature conditions of its highest density (at 4 degrees Celsius), but at zero degrees Celsius. These are the properties of fresh water. However, freezing of sea water occurs at lower temperatures: minus 1.9 degrees Celsius, with a salinity of 35%.
- Water has a very high heat capacity, but heats up relatively little. Water also has a fairly high latent heat of fusion (about 80 cal/g), as well as evaporation (about 540 cal/g). Water can absorb significant amounts of additional heat. The temperature during freezing or boiling remains unchanged.
- Distilled water practically does not conduct electric current, but the presence of even a small amount of salts in water significantly increases its conductive properties.
Properties of snow:
- When mixing salt with snow, two processes are observed: the destruction of the crystalline structure of the salt, which occurs with the absorption of heat, and the hydration of ions. The last process occurs with the release of heat into the environment. For table salt and calcium chloride, the first process prevails over the second. Therefore, when snow is mixed with these salts, heat is actively removed from the environment. Another feature of salt solutions is that their freezing point is below 0 degrees. To make the snow on the sidewalks melt at temperatures below 0 degrees, these salts are sprinkled on it.
- Snow has an amazing property - memory. It keeps traces. You can, for example, study physics using the tracks. The larger the animal, the deeper its footprint, therefore, the more pressure it exerts on the snow. A dog's tracks are deeper than those of her puppies. Mice and caresses leave shallow lines. Nature has provided ungulates with the ability to spread their hooves and increase the area of support. This helps them in winter, when moving through snowy forests and fields, not to sink so deeply into the snow.
1.2 The importance of water crystallization for flora and fauna
We love snow not only because it gives us magnificent winter landscapes. Our love for snow has many rational reasons. “Snow in the fields means bread in the bins,” “Winter without snow means summer without bread,” old Russian proverbs rightly say. Snow cover is a huge supply of moisture, much needed by the fields, and at the same time it is a kind of giant blanket that protects the surface of the earth from cold winds. Academician B.I. Vernadsky emphasized that snow cover is “not just a warm cover for winter crops, it is a life-giving cover”; in the spring it provides melt water saturated with oxygen. It is known that the amount of nitrogen compounds in the soil in summer is proportional to the height of the melted snow cover. It is not without reason that snow reclamation is considered today as one of the most important conditions for obtaining high and sustainable yields.
Snow reserves significantly affect water levels in rivers and determine climate changes over large areas.
In addition, snow is a good building material for various buildings in the north - from igloos (Eskimo dwellings) to large warehouses. There is the world's largest hotel, made entirely of ice and snow, located in Swedish Lapland, 200 kilometers from the Arctic Circle.
It serves as the basis for winter roads and even airfields.
Thanks to snow, every year we admire fabulous winter landscapes, play snowballs, build snow towns, fortresses, skiing, sledding, and a wonderful New Year's holiday comes to us in the snow.
The importance of ice is difficult to underestimate. Ice has a great influence on the living conditions of plants and animals, and on various types of human economic activity. Covering the water from above, ice plays in nature the role of a kind of floating screen, protecting rivers and reservoirs from further freezing and preserving life in the underwater world. If the density of water increased when it froze, the ice would be heavier than water and begin to sink, which would lead to the death of all living creatures in rivers, lakes and oceans, which would freeze completely, turning into blocks of ice, and the Earth would become an ice desert, which is inevitable would lead to the death of all living things.
Ice can cause a number of natural disasters with harmful and destructive consequences - icing of aircraft, ships, structures, road surfaces and soil, hail, blizzards and snow drifts, river congestion with floods, ice avalanches, etc. Natural ice is used for storing and cooling food products, biological and medical preparations, for which it is specially produced and prepared.
1.3 Selection and justification of experiments for research
To conduct experiments with water, it is necessary to select those that most fully characterize and confirm the properties of water.
The analysis showed that this will be best achieved by performing the following experiments:
- Freezing of salt water.
- Expansion of water when freezing.
- Freezing of liquid due to external influence of snow.
- Freezing soap bubbles.
- Icicle fusion.
- The creaking of dry snow.
- Freezing to the surface.
Conducting research
2.1 Preparation of the material part
The following were taken for the experiments:
- objects - a saucepan, a glass bottle, a plastic bottle, disposable glasses, thin copper wire, a straw;
- substances - snow, icicle, salt, water, soap solution, juice.
2.2 Conducting experiments with a description of the main results
Freezing of salt water.
Pour water into two molds - clean and very salty. Take the molds out into the cold or put them in the freezer. You will notice that clean fresh water has turned into ice, and salt water will freeze in very severe frost.
Water freezes not at the temperature conditions of its highest density (at 4 degrees Celsius), but at zero degrees Celsius. These are the properties of fresh water.
However, sea ice differs from freshwater ice in a number of respects. Salt water has a lower freezing point as salinity increases. In the salinity range from 30 to 35 ppm, the freezing point varies from -1.6 to -1.9 degrees. The formation of sea ice can be thought of as the freezing of fresh water, displacing salts into cells of sea water within the ice column. When the temperature reaches freezing, ice crystals form and “surround” the unfrozen water.
Expansion of water when freezing.
Fill a plastic cup, a plastic bottle and a glass bottle with water. Leave them out in the cold. When water freezes, it increases in volume, “crawls out” of the glass, and breaks the glass bottle even when it is half filled. The plastic bottle remains without visible changes.
When water freezes, it has unique expansion properties. Thanks to these properties, ice floats on water, which is in the form of a liquid.
In winter, due to this property of water, accidents occur in water pipelines. In severe frosts, the main cause of such accidents is the freezing of flowing water. It expands, so that the resulting ice easily breaks the pipes, since the density of ice is 917 kg/m3, and the density of water is 1000 kg/m3, that is, the volume increases by 1.1 times, which is quite significant.
Freezing of liquid due to external influence of snow.
Pour juice into a plastic glass (test tube) and place it in a pan with salted snow. The juice will freeze, and very soon you will be enjoying popsicles.
When mixing salt with snow, the crystalline structure of the salt is destroyed, which occurs with the absorption of heat. Therefore, when snow is mixed with salt, heat is actively removed from the juice and the juice turns into ice.
Freezing soap bubbles.
Prepare a soap solution. In cold weather, keep the solution in a mitten so that it does not freeze. Blow bubbles with a juice straw. Due to the temperature difference between inside and outside the bubble, a large lifting force arises, instantly carrying the bubbles upward. A thin film of soap freezes quickly in the cold, turning bubbles into ice balls.
Thus, the thinnest film of the soap bubble freezes in a matter of seconds.
Icicle fusion.
Take the icicle. Throw a thin wire over it, the ends of which are weighted with weights. Watch how the wire melts the ice and penetrates deeper into the icicle. The water above the icicle freezes again.
This confirms the property of heat absorption by a larger mass of ice.
Ice grows from below, immediately above the wire, as the melt water flowing down freezes upon contact with the cold walls of the icicle.
The creaking of dry snow.
Pour granulated sugar into a plate and start crushing it with a spoon. You will hear a characteristic creak. Wet the sand and rub again. The creaking disappeared. On frosty days, sound travels long distances.
Snow creaks only in cold weather (below -5°C), and the sound of the creaking changes depending on the air temperature - the stronger the frost, the higher the pitch of the creaking. With enough experience, you can estimate the air temperature by the sound that creaking snow makes. The creaking is formed due to the fact that the smallest snow crystals are destroyed under pressure. Moreover, each of them individually is very small to produce a sound accessible to the human ear, but together they break quite loudly. Increasing frosts make ice crystals harder and more fragile. With every step, the ice needles break. At air temperatures below -50°C, the creaking of snow becomes so strong that it can be heard through triple glass (this is also facilitated by the high density of frosty air).
Freezing to the surface.
Add table salt to the pan with snow in a ratio of approximately 1 to 6. Stir the mixture thoroughly. If you now want to move the pan, you will have to lift it along with the stool.
This also confirms the absorption of heat from the environment.
When salt is mixed with snow, a solution is formed, accompanied by strong cooling due to the large absorption of heat by the ice when it melts and by the salt when it dissolves. For example, the temperature of a mixture of 29 grams of salt and 100 grams of ice drops to -21°C. And if you take 143 grams of salt and 100 grams of ice, the temperature can be lowered to -55°C.
2.3 Proposals for conducting experiments
It is advisable to conduct experiments to study the properties of water in classes in secondary and primary schools.
At the same time, for elementary school children, it is recommended to conduct experiments No. 1 and 2 at home under the supervision of parents.
For secondary school students, it is possible to conduct experiments No. 3, 6 and 7 in lessons under the guidance of a teacher, and experiments No. 4 and 5 - optionally or independently at home.
How much fluid can you drink?
We can drink as much as we want, but another interesting research study showed that only two liters can be considered normal for a person . Is it a lot or a little? Of course, the calculation was based on the fact that the experiment involved adults who consume enough water, much more than children. It is worth noting the fact that the indicated average value of two liters can in no way serve as a guide for those people who previously drank less or more water. Agree that with a height of 150 cm and a weight of 55 kilograms, a person will be able to drink much less water than if he were almost two meters tall and weighed about 100 kilograms. Therefore, the values given by scientists do not always need to be observed. Moreover, an overdose of water also carries with it some health problems.
The simplest of problems: kidney overload. Fluid passes through the kidneys, which we never feel until something unfortunate happens to the organs. But every organ must rest: even individual heart muscles work half as long as their “rest” lasts. If you constantly overload your kidneys with water, they will eventually work less efficiently. Therefore, it is worth thinking about how to make drinking water less hazardous to your health. That is, drink enough liquid or, conversely, reduce the amount you drink.
