Evaporation process. Evaporation - write to Antoshka

The surrounding world is an interconnected organism in which all processes and phenomena of living and inanimate nature occur for a reason. Scientists have proven that even minor human interventions bring colossal changes. Despite this, people forget that they are also an integral part of the world around them. In this regard, changes are taking place in humanity as a whole.

Children begin to be taught everything about life processes and natural phenomena already at school, which is very important for their further understanding of what is happening around them. As you know, the topic “Evaporation” (8th grade) is studied precisely as part of the secondary school curriculum, when students are already ready to think about problems.

How does evaporation occur?

Everyone knows what evaporation is. This is the phenomenon of transformation of substances of different consistencies into a state of vapor or gas. It is known that this process occurs at the appropriate temperature.

Usually, under natural conditions, many substances (both solid and liquid) practically do not evaporate or do so very slowly. But there are also samples, for example, camphor and most liquids, which under normal conditions evaporate very quickly. That's why they were called flying. You can notice this process with the help of smell, since many bodies are toxic.

The evaporation of a liquid (water, alcohol) can be monitored by observing it over a period of time. Then the volume of this substance begins to decrease.

The basis of life on Earth

As you know, water is the existence of the surrounding world. Without it, no existence is possible, since all living beings consist of 75% water.

This is a special compound whose properties are exceptional. And only thanks to such anomalies of this phenomenon is life in the form that now exists on the planet possible.

Humanity has been interested in this miracle since ancient times. Even the philosopher Aristotle in the 4th century BC declared that water is the beginning of everything. In the 17th century, the Dutch mechanic, physicist, mathematician, astronomer and inventor Huygens recommended establishing the coefficients of boiling water and thawing ice as the main levels of the thermometer scale. But humanity learned what evaporation was much later. In 1783, the French naturalist and founder of modern chemistry Lavoisier reproduced the formula - H2O.

Properties of water

One of the incredible qualities of this substance is the ability of H2O to exist in three different states under normal conditions:

• in solid (ice);
• fluid;
• gaseous (evaporation of liquid).

In addition, water has a very high density when compared to other substances, as well as a high heat of vaporization and latent heat of fusion (the amount of heat absorbed or released).

H2O has one more quality - the ability to vary its density depending on changes in the thermometer readings. And the most amazing thing is that if this quality did not exist, the ice would not be able to float, and the seas, oceans, rivers and lakes would freeze to the bottom. Then life on earth could not exist, because water bodies are the first refuge of microorganisms.

H2O cycle in nature

How does this process happen? Circulation is a continuous procedure, because everything in the world is interconnected. With the help of the cycle, conditions are created for the existence and development of life. It occurs between bodies of water, land and the atmosphere. For example, when clouds collide with cold air, large drops are formed, which subsequently fall in the form of precipitation. Then the process of evaporation occurs, during which the sun heats the plane of the earth, reservoirs, and the liquid rises upward into the atmosphere.

Vegetation takes moisture from the soil, and water circulation occurs from the surface of the leaves. This procedure is called transpiration and is a physical and biological process.

The layers of the atmosphere, those close to the ground, then become lighter and begin to move upward. The smallest droplets of water in the atmosphere are replenished approximately every eight to nine days.

Evaporation occurs as a result of the cycle, and it is an important component in the circulation of H2O in nature. This process consists of the transformation of water from a liquid or solid state into a gaseous state and the release of inaccessible vapor into the air.

Volatility and evaporation

What is the difference between the concepts “evaporation” and “evaporation”? Let's look at the first term first. This is an indicator of the climate of the area, which determines how much liquid has evaporated from the surface to the maximum. If we take into account that the humidity of the territory, as noted by G.N. Vysotsky, consists of the ratio of precipitation to evaporation, then this is the most important indicator of the microclimate.

There is also a certain dependence: if evaporation is less, then humidity is greater. The described process is based on air humidity and depends specifically on them.

What is a phenomenon in which, in a certain phase, a substance transforms from liquid into vapor or gas. This process is called condensation. If we compare these two phenomena, it is easy to determine how accessible the water or ice resources are for evaporation.

Evaporation process: conditions

There is always some amount of H2O molecules present in the air. This indicator varies depending on certain conditions and is called humidity. This is a coefficient that measures the volume in the atmosphere. Depending on this, the climate of the areas varies. Humidity is everywhere. There are two types of it:

1. Absolute - the number of water molecules in one cubic meter of atmosphere.
2. Relative - percentage ratio of vapor to air. For example, if the humidity is 100%, this means the atmosphere is completely saturated with water particles.

The higher the evaporation temperature, the more H2O molecules are contained in the air. So, if the relative humidity on a hot day is 90%, then this is an indicator that the atmosphere is extremely saturated with tiny droplets.

Particulars

Let’s say that in a room with high humidity, the water standing in it will not evaporate at all. Although if the air is dry, then the process of saturation with steam will become continuous until it is completely filled with it. When the air suddenly cools, the water vapor that previously saturated it will evaporate without stopping and settle in the form of dew. But if the air, which is sufficiently humidified, is heated, the saturation process will resume.

The higher the temperature, the more intense the evaporation occurs, and the so-called elasticity of the vapors that saturate the space increases. Boiling occurs when the vapor pressure is equal to the gas pressure that surrounds the liquid. The boiling point varies depending on the gas pressure around it and becomes higher as it increases.

Does evaporation occur quickly?

As you know, the process of converting water into steam is directly related to the existence of liquids. Therefore, we can summarize that this phenomenon is very important for nature and industry.

In the process of studying and experimenting, the rate of evaporation was revealed. In addition, some phenomena accompanying it became known. But they look very contradictory and to this day their nature is not yet clear.

Note that the rate of evaporation depends on many factors. It can be affected by:

• size and shape of the container;
• external weather conditions;
• t° liquid;
• atmospheric pressure;
• composition and origin of water structure;
• the nature of the surface from which evaporation occurs;
• some other reasons, for example, electrification of the liquid.

Once again about water

Evaporation occurs from anywhere there is liquid: lakes, ponds, wet objects, the bodies of people and animals, leaves and stems of plants.

For example, during its short life, a sunflower releases 100 liters of moisture into the air. And the oceans of our planet release approximately 450,000 cubic meters of liquid per year.

The temperature of water evaporation can be any. But when it gets warmer, the liquid transition process accelerates. Note that during the summer heat, puddles on the surface of the earth dry out much faster than in spring or autumn. And if it’s windy outside, then, accordingly, evaporation occurs even more intensely than in situations where the air is calm. Snow and ice also have this property. If you hang your laundry outside to dry in winter, it will first freeze and then dry out after a few days.

The temperature of water evaporation of 100°C is the most intense factor at which the named process achieves its highest result. At this time, boiling occurs when the liquid intensively turns into steam - a transparent, invisible gas.

If examined under a microscope, it consists of single H2O molecules located far from each other. But when the air cools, water vapor becomes visible, for example as fog or dew. In the atmosphere, this process can be observed thanks to clouds, which appear due to the transformation of water droplets into visible ice crystals.

Nature statistics

So, we found out what evaporation is. Now let us note the fact that it is closely related to air temperature. Consequently, during the day, the largest number of cubic meters of water turns into steam around noon. In addition, this process is most intense during the warm months. The strongest evaporation in the annual cycle occurs in mid-summer, while the weakest evaporation occurs in winter.

Every person is responsible for the state of the environment. To understand this proposition, it is necessary to grasp a simple calculation. Let's imagine that a person talks about his helplessness in relation to preventing an environmental disaster and believes that he is unable to do anything. But if you multiply one insignificant action of an individual by 6.5 billion people on earth, it will become clear why it is worth arguing this way.

Scientists have been concerned about this for a very long time. The first studies were carried out in Antiquity, when there was still little knowledge. But even then people wanted to know all the secrets that water conceals. Of course, the greatest amount of research and discoveries useful for life have been made over the past 200 years. Despite the rapid development of physics since the seventeenth century, few people studied water and the only thing that was done in those years was water purification.

And even the fact that hot food existed for thousands of years did not bother scientists. Its effect on the body did not immediately interest physicists. And yet the first steps were taken in the 16th century. At that time, they studied, first of all, the effects of moisture and steam on humans. After all, he was the only object of its kind that could be studied. First of all, we compared the temperatures, compared the characteristics of the impact and agreed on what could have both beneficial and negative effects. It is enough to heat the steam too much, to maintain evaporation for too long - in other words, anything that would be “too much” for human skin would be harmful.

Steam for personal use

Therefore, in the search for new discoveries, they tried to clarify the permissible steam parameters. More accurate research began much later, when steam began to be used in industry, when the development of steam engines transformed the world. It became necessary to accurately calculate the force that steam carries in itself, which can move pistons and rotate wheels. Classical Newtonian physics ceased to be useful at that moment - it was created for solids, and moisture was not such a thing. Even if there is a little liquid on the surface of the body, then even in this case it would be impossible to calculate the potential interactions of the bodies.

Due to the evaporation of water, changes also occurred in the interactions of bodies. Cooling, deformation - all this was a consequence of the release of liquid molecules from the main volume of moisture. I wonder how strong the impact could be? Let's imagine an ordinary teapot. Three liters of water are poured into it. To completely turn three liters of water into steam on a gas stove, it takes at least an hour and a half (here everything depends on the shape of the kettle and the power of the stove). Three liters of water contain 10 26 molecules. The effect of molecules that break away from the liquid on the liquid itself is only thousandths. This is the reason why no one can notice the impact. In addition, from a perfectly flat surface, any molecule can come off at an angle from 0 to 180 degrees, which on average (according to probability theory) gives a reverse force directed strictly downward.

Watch the video film “What happens when water evaporates from open surfaces”

MCT and some liquid

Of course, all this is somewhat difficult to understand, because the molecular kinetic theory was developed already in the 19th century, when physics reached the constituent parts of elementary substances. But still, without this, it is impossible to understand why the distance between the molecules that evaporate from the surface of the water increases. Moreover, it increases immediately for several reasons.

The first reason is very simple and understandable to everyone: when moving from one state of aggregation to another, the molecules move apart in width, the gaps between them increase, and the interaction decreases. The second reason is also not complicated: when heated, molecules move faster, and therefore they gain more energy and, due to it, get the opportunity to break away from the influence of other molecules located nearby. If you think about it, then the transition to another state of aggregation is also possible only for one or another substance. That's why it all comes down to just increasing kinetic energy.

When water evaporates from the surface of a body, the distance between its molecules increases... does it always?

Let's see what this means. Let's remember simple problems about a ball: we pumped it up in a warm room, took it out into the cold - and it became soft. The fact is that molecules are constantly in motion. It is impossible to detect a state (except for absolute zero, which is also unattainable) in which the molecules would not be in motion. Therefore, among the states +100 and -50, there is only a difference in the speed at which the molecules move. It may seem that the difference is insignificant, but in fact, with a serious change in temperature, the speed of movement increases many times.

Damage caused by a steam boiler

Remembering the dependence of gas pressure on the walls of a vessel on temperature, we find that when it increases by 100 degrees, the pressure increases tens of times. Consequently, the speed increases by the same amount. Considering with normal, high and excess pressure, one can recall the explosion of a boiler that is filled with excessively hot steam, half-flat tires on cars in the cold, as well as many other examples. And if in itself it has some influence, then its steam usually puts much stronger pressure on the walls of the vessel.

Since there is almost always moisture on the surface of the body and on the surface of water (even at minimal humidity and low temperature), pressure is observed under any terrestrial conditions. They are very diverse: Antarctica and Africa seem to be very far apart from each other, but in fact the same humidity can be observed in both places.

As for the influence of humidity and steam on bodies, dozens of factors need to be taken into account: speed of movement, air humidity, ambient temperature, type of environment, and several others. For example, the trajectory of a bullet, the degree of deformation of the body, and much, much more depend on them.

molecular bond

But even when the distance between molecules is large, there is a bonding force. Due to its impact, kinetic energy can increase or decrease. According to the law of universal gravitation, two molecules attract with a force proportional to their masses and inversely proportional to the square of the distance between them. That is, the force decreases with increasing distance, but never completely disappears. Therefore, even very heated steam never breaks up into individual molecules, no matter how high the temperature.

The path to the particle can be reduced, but another theory is already at work here, the theory of an ideal gas. Considering it approximately, one can understand that an increase in temperature does not always lead to a change in gas density. There are three main parameters: temperature, volume and pressure. The higher the temperature, the higher the pressure at a constant volume. If the pressure is increased, then, with a constant volume, the temperature will increase - but the distance will not change. There is nothing surprising, because classical isobaric processes have just been considered.

Physics and teapot

When working with water, physics will be encountered constantly. It is impossible to get rid of its laws under any circumstances. When the movement of a wave or the flight of a molecule from the surface of an object is studied, when the movement of a liquid in a vessel is considered, MKT - molecular kinetic theory - is used everywhere. And if physics was boring at school, then even to study everyday things it is worth applying some interesting theories. By the way, the behavior of a liquid in a vessel can be examined in great detail using the example of a teapot. When a liquid evaporates or heats up, individual areas move. Some molecules escape during evaporation, while others come back. If 100% return occurs, the system is called saturated. At zero humidity, the number of returning molecules tends to zero.

This is how, when any physical process occurs, you can use mathematical and physical laws to accurately calculate everything down to the hundredth. But if you just want to know the laws that water obeys, then you just need to read our articles, which reveal not only the nature of the liquid, but also the secrets it keeps.

Water in the atmosphere. Properties of water

Water is everywhere on earth. Oceans, seas, rivers, lakes and other bodies of water occupy 71% of the earth's surface. Water, which is contained in the atmosphere, is the only substance that can be there in all three phase states (solid, liquid and gaseous) at the same time.

The most important physical properties of water for meteorology are presented in Table 6.

Table 6 - Physical characteristics of water (Rusin, 2008)

Properties of water important for climate formation:

· water is an absorber of radiant energy;

· has one of the highest values ​​of specific heat capacity among other substances on earth (this affects the difference in heating of land and sea, the penetration of radiation and heat deep into the soil and water bodies);

· ideal (almost) solvent;

· the dipole (bipolar) structure of water molecules provides a high boiling point (without hydrogen bonds, the boiling point would be -80°C).

Expands when frozen, unlike other substances that contract. (the maximum density of water is observed at a temperature of +4°C; the density of ice is less than the density of water: distilled by 1/9, sea by 1/7; lighter ice floats on the surface of the water).

Thanks to the processes of evaporation and condensation, the water cycle continuously occurs in the atmosphere, in which a significant mass of it participates. On average, the long-term water cycle is characterized by the following data (Table 1):

Table 1 - Characteristics of the water cycle on Earth (Matveev, 1976)

	Precipitation, mm/year	Evaporation, mm/year	Runoff, mm/year
Continents
World Ocean
Earth

A layer of water 1127 mm thick (or 4.07 10 17 kg of water) evaporates from the surface of the oceans (361 million km 2) during the year, and 446 mm (or 0.66 10 17 kg of water) from the surface of the continents. The thickness of the layer of precipitation falling per year on the oceans is 1024 mm (or 3.69 10 17 kg of water), on the continents - 700 mm (or 1.04 10 17 kg of water). The amount of precipitation on the continents significantly exceeds evaporation (by 254 mm, or 0.38·10 17 kg of water). This means that a significant amount of water vapor reaches the continents from the oceans. On the other hand, water that has not evaporated on the continents (254 mm) flows into rivers and further into the ocean. On the oceans, evaporation exceeds (by 103 mm) the amount of precipitation. The difference is replenished by water runoff from the oceans.

Evaporation and volatility

Water enters the atmosphere as a result of evaporation from the Earth’s surface (reservoirs, soil); it is secreted by living organisms in the process of life (respiration, metabolism, transpiration in plants); it is a by-product of volcanic activity, industrial production and the oxidation of various substances.

Evaporation(usually water) - the entry of water vapor into the atmosphere due to the separation of the fastest moving molecules from the surface of water, snow, ice, wet soil, drops and crystals in the atmosphere.

Evaporation from the surface of the earth is called physical evaporation. Physical evaporation and transpiration together - evapotranspiration.

The essence of the evaporation process is the separation of individual water molecules from the water surface or from moist soil and the transfer of air as water vapor molecules. The steam contained in the atmosphere condenses when the air cools. Condensation of water vapor can also occur through sublimation (the process of direct transition of a substance from gaseous to solid, bypassing liquid). Water is removed from the atmosphere by precipitation.

The molecules of a liquid are always in motion, and some of them can break through the surface of the liquid and escape into the air. Those molecules come off whose speed is higher than the speed of movement of molecules at a given temperature and is sufficient to overcome the forces of adhesion (molecular attraction). As the temperature rises, the number of molecules coming off increases. Vapor molecules can return from air to liquid. When the temperature of a liquid increases, the number of molecules leaving it becomes greater than the number returning, i.e. liquid evaporates. Lowering the temperature slows down the transition of liquid molecules into air and causes steam to condense. If water vapor enters the air, it, like all other gases, creates a certain pressure. As water molecules move into the air, the vapor pressure in the air increases. When a state of mobile equilibrium is reached (the number of molecules leaving the liquid is equal to the number of molecules returning), evaporation stops. This condition is called saturation , water vapor in this state – saturating , and the air rich . The pressure of water vapor at saturation is called saturated water vapor pressure (E), or saturation elasticity, or maximum elasticity.

Until the saturation state is reached, the process of water evaporation occurs, and the elasticity of water vapor (e) above the liquid is less than the maximum elasticity: e<Е.

If the number of returning water molecules is greater than the number of escaping ones, then the process of condensation or sublimation takes place (above the ice): e>E.

The pressure of saturated water vapor depends on

· air temperature,

on the nature of the surface (liquid, ice),

on the shape of this surface,

water salinity.

Most of the water vapor enters the atmosphere from the surface of the seas and oceans. This especially applies to humid, tropical regions of the Earth. In the tropics, evaporation exceeds precipitation. At high latitudes the opposite relationship occurs. In general, throughout the globe, the amount of precipitation is approximately equal to evaporation.

Evaporation is regulated by certain physical properties of the area, in particular the temperature of the surface of the water and large bodies of water, and the prevailing wind speeds there. When the wind blows over the surface of the water, it carries the moistened air aside and replaces it with fresh, drier air (i.e., advection and turbulent diffusion are added to molecular diffusion). The stronger the wind, the faster the air changes and the more intense the evaporation.

Evaporation can be characterized by the speed of the process. Evaporation rate (V) is expressed in millimeters of water layer evaporated per unit time from a unit surface. It depends on the saturation deficit, atmospheric pressure and wind speed.

Evaporation is difficult to measure under real conditions. To measure evaporation, evaporators of various designs or evaporation pools (with a cross-sectional area of ​​20 m 2 or 100 m 2 and a depth of 2 m) are used. But the values ​​obtained from evaporators cannot be equated to evaporation from a real physical surface. Therefore, they resort to calculation methods: evaporation from the land surface is calculated based on data on precipitation, runoff and soil moisture content, which are easier to obtain by measurements. Evaporation from the sea surface can be calculated using formulas close to the overall equation.

A distinction is made between actual evaporation and evaporation.

Volatility– potential evaporation in a given area under the existing atmospheric conditions.

This means either evaporation from the surface of water in the evaporator; evaporation from the open water surface of a large body of water (natural freshwater); evaporation from the surface of excessively moist soil. Evaporation is expressed in millimeters of the layer of evaporated water per unit of time.

In polar regions, evaporation is low: about 80 mm/year. This is due to the fact that low temperatures of the evaporating surface are observed here, and the pressure of saturated water vapor E S and the actual pressure of water vapor are small and close to each other, therefore the difference (E S – e) is small.

In temperate latitudes, evaporation changes over a wide range and tends to increase when moving from the northwest to the southeast of the continent, which is explained by an increase in the saturation deficit in the same direction. The lowest values ​​in this belt of Eurasia are observed in the north-west of the continent: 400–450 mm, the highest (up to 1300–1800 mm) in Central Asia.

In the tropics evaporation is low on the coasts and increases sharply in inland parts to 2500–3000 mm.

At the equator evaporation is relatively low: does not exceed 100 mm due to the small value of the saturation deficit.

Actual evaporation on the oceans coincides with evaporation. On land it is significantly less, mainly depending on the moisture regime. Difference between evaporation and precipitation can be used to calculate air humidification deficit.

Solar energy powers an incredibly powerful heat engine, which, overcoming gravity, easily lifts a huge cube into the air (each side is about eighty kilometers). Thus, a meter thick layer of water evaporates from the surface of our planet every year.

During evaporation, a liquid substance gradually turns into a vapor or gaseous state after the smallest particles (molecules or atoms), moving at a speed sufficient to overcome the cohesive forces between the particles, break away from the surface.

Despite the fact that the process of evaporation is better known as the transition of a liquid substance into vapor, there is dry evaporation, when at sub-zero temperatures ice passes from a solid state to a vapor state, bypassing the liquid phase. For example, if you hang wet laundry to dry in the cold, it freezes and becomes very hard, but after some time it softens and becomes dry.

How liquid evaporates

The molecules of the liquid are located almost right next to each other, and, despite the fact that they are connected by forces of attraction, they are not tied to certain points, and therefore move freely throughout the entire area of ​​​​the substance (they constantly collide with each other and change their speed).

Particles that go to the surface gain momentum during their movement, sufficient to leave the substance. Once at the top, they do not stop their movement and, having overcome the attraction of the lower particles, fly out of the water, transforming into steam. In this case, some of the molecules return to the liquid due to chaotic movement, while the rest go further into the atmosphere.

Evaporation does not end there, and the next molecules break out to the surface (this happens until the liquid completely evaporates).

If we are talking, for example, about the water cycle in nature, we can observe the process of condensation when steam, having concentrated, returns back under certain conditions. Thus, evaporation and condensation in nature are closely related to each other, since thanks to them there is a constant exchange of water between the earth, land and the atmosphere, due to which the environment is supplied with a huge amount of useful substances.

It is worth noting that the intensity of evaporation for each substance is different, and therefore the main physical characteristics that affect the rate of evaporation are:

1. Density. The denser the substance, the closer the molecules are to each other, the more difficult it is for the upper particles to overcome the force of attraction of other atoms, therefore, the evaporation of the liquid occurs more slowly. For example, methyl alcohol evaporates much faster than water (methyl alcohol - 0.79 g/cm3, water - 0.99 g/cm3).
2. Temperature. The rate of evaporation is also affected by the heat of evaporation. Despite the fact that the evaporation process occurs even at sub-zero temperatures, the higher the temperature of the substance, the higher the heat of evaporation, which means the faster the particles move, which, increasing the intensity of evaporation, leave the liquid en masse (therefore, boiling water evaporates faster than cold water). Due to the loss of fast molecules, the internal energy of the liquid decreases, and therefore the temperature of the substance decreases during evaporation. If at this time the liquid is near a heat source or directly heated, its temperature will not decrease, just as the intensity of evaporation will not decrease.
3. Surface area. The larger the surface area a liquid occupies, the more molecules evaporate from it, the higher the evaporation rate. For example, if you pour water into a jug with a narrow neck, the liquid will disappear very slowly as the evaporated particles begin to settle on the narrowing walls and descend. At the same time, if you pour water into a bowl, the molecules will freely leave the surface of the liquid, since there will be nothing for them to condense on in order to return to the water.
4. Wind. The evaporation process will be much faster if air moves above the container in which the water is located. The faster he does this, the greater the evaporation rate. It is impossible not to take into account the interaction of wind with evaporation and condensation. Water molecules, rising from the ocean surface, partially return back, but most of them condense high in the sky and form clouds, which the wind drives to land, where the drops fall in the form of rain and, penetrating into the ground , after some time they return to the ocean, supplying vegetation growing in the soil with moisture and dissolved minerals.

Role in plant life

The importance of evaporation in the life of vegetation is difficult to overestimate, especially considering that a living plant consists of eighty percent water. Therefore, if a plant does not have enough moisture, it may die, since the nutrients and microelements necessary for life will not be supplied to it along with water.

Water, moving through the plant body, transports and forms organic substances inside it, for the formation of which the plant needs sunlight.

But here evaporation plays an important role, since the sun's rays have the ability to heat objects extremely strongly, and therefore can cause the death of a plant from overheating (especially on hot summer days). To avoid this, water evaporates from the leaves, through which a lot of liquid is released at this time (for example, from one to four glasses of water evaporate from corn per day).

This means that the more water enters the plant’s body, the more intense the evaporation of water by the leaves will be, the plant will cool more and grow normally. You can feel the evaporation of water by plants if you touch the green leaves while walking on a hot day: they will definitely be cool.

Connection with a person

The role of evaporation in the life of the human body is no less important: it fights heat through sweating. Evaporation usually occurs through the skin, as well as through the respiratory tract. This can be easily noticed during illness, when the body temperature rises, or during exercise, when the rate of evaporation increases.

If the load is small, the body leaves from one to two liters of fluid per hour, with more intense sports, especially when the external temperature exceeds 25 degrees, the intensity of evaporation increases and from three to six liters of fluid can be released with sweat.

Through the skin and respiratory tract, water not only leaves the body, but also enters it along with environmental evaporations (it’s not for nothing that doctors often prescribe seaside holidays to their patients). Unfortunately, along with useful elements, harmful particles often get into it, including chemicals and harmful fumes, which cause irreparable damage to health.

Some of them are toxic, others cause allergies, others are carcinogenic, others cause cancer and other equally dangerous diseases, while many have several harmful properties at once. Harmful fumes enter the body mainly through the respiratory system and skin, after which, once inside, they are instantly absorbed into the blood and spread throughout the body, causing toxic effects and causing serious illnesses.

In this case, a lot depends on the area where the person lives (near a factory or plant), the premises in which he lives or works, as well as the time spent in conditions hazardous to health.

Harmful fumes can enter the body from household items, for example, linoleum, furniture, windows, etc. In order to preserve life and health, it is advisable to avoid such situations and the best way out would be to leave the dangerous territory, including exchanging an apartment or job, and when arranging your home, pay attention to the quality certificates of the purchased materials.

Department of Education, Youth Policy, Physical Culture and Sports

administration of Morgaushsky district

Municipal educational institution

"Kashmash basic secondary school"

Research

Subject: "Evaporation"

Municipal educational institution "Kashmashskaya school"

Zaitseva Victoria

Supervisor:

village Kashmashi - 2010

Introduction
Main part:
Conclusion
Application
Literature

Introduction

Relevance of the topic:

In nature, water constantly evaporates from the surface of seas, rivers, lakes, and soil. It rises high in the form of steam. The steam cools there and forms many water droplets or tiny pieces of ice. Clouds are formed from these droplets and pieces of ice. From the cloud, water returns to the earth in the form of rain and snow.

Topic problem:

Why does wet laundry dry and water poured on the floor disappear?

Theme object:

The process of evaporation of substances

Topic subject:

Liquids and vapors

Goal of the work: study of the evaporation process in domestic conditions.

Job objectives:

1. Study the literature on the topic of work;

2. Experimentally prove how the evaporation process occurs;

3. Identify the reasons affecting the evaporation processes.

Methods:

Study of literature;

Observation;

ChapterI Evaporation

Evaporation is the process by which a liquid gradually changes into air in the form of vapor or gas.

All liquids evaporate, but at different rates.

When the liquid is heated, evaporation occurs faster - in a warm liquid the speed of movement of molecules is greater, more molecules have a chance to leave the liquid.

The larger the surface area of ​​the evaporating liquid, the faster the evaporation occurs. Water in a round frying pan will evaporate faster than in a tall jug.

By wetting your hand with some quickly evaporating liquid (alcohol, perfume), you can feel a strong cooling of the wetted area. The cooling will increase if you blow on your hand.

Water cycle in nature

In extreme heat, rivers, ponds and lakes become shallow, water evaporates, that is, it goes from a liquid state to a gaseous state - it turns into invisible steam. During the day, the water of puddles, ponds, lakes, rivers, seas, moisture contained in plants is heated by the Sun and evaporates, and the more quickly it is heated. You can notice this if two identical plates are filled with different amounts of water and one of them is placed in the sun, and the other is placed in the shade. Where water is heated by the sun's rays, it will evaporate noticeably faster. Accelerates evaporation and wind. A wet piece of paper in the wind will dry faster than one left where the air is calm and still.

On hot, dry days, a person sweats, but the sweat doesn’t bother him much: it dries instantly. And when it’s humid and hot, even your clothes get wet from sweat. But if moisture constantly evaporates from seas, rivers, lakes, if it leaves plants and disappears in the atmosphere, then why doesn’t the Earth dry out?

This does not happen because the water is in a constant cycle. Having evaporated, it rises along with the heated air, taking the form of tiny droplets.

Conclusion:

The process of evaporation is a very interesting phenomenon, it is interesting to observe it and note how often it occurs in our lives.

I think that science will use the evaporation process more than once for the benefit of humans and our planet.

ChapterII Practical experiences

The rate of evaporation depends on:

1) liquid surface area;

2) temperature;

3) movement of molecules above the surface of the liquid (wind);

4) type of substance;

1. Dependence of evaporation on the area of ​​the evaporated surface if the temperature of the liquid is the same.

Progress of the experiment:

Pour the same amount of water into the glass and saucer. Let's leave it until the morning.

The next morning we see that the water in the saucer has evaporated (the volume of liquid has become smaller), but there is still water in the glass.

Conclusion: The larger the surface of the evaporating liquid, the faster the evaporation occurs, since the number of evaporating molecules will be greater over a larger area.

2. Dependence of evaporation on temperature

Progress of the experiment:

I took 2 identical vessels, poured cold water into one of them, and hot water into the other. The water level was the same. After some time, there was less liquid in the vessel containing hot water.

Conclusion: The higher the temperature, the faster the evaporation rate

3. Dependence of evaporation on wind.

Progress of the experiment:

The rate of evaporation depends on the movement of air over the free surface of the liquid. When we create wind, evaporation happens faster

Apply the same amount of water to 2 sheets of paper. We will create a wind over one sheet of paper using a notebook or a hairdryer.

Conclusion: If the air above the liquid moves, the rate of evaporation increases because the air flow helps the liquid molecules break away from the surface and change into a vapor state. Hot air will speed up this process.

Dependence of evaporation on the type of substance.

Progress of the experiment:

To conduct this experiment, I took two paper napkins. She poured a little water on the first one, and sprayed perfume on the second one. Then I began to observe the evaporation of liquids.

The perfume evaporated most quickly, leaving no trace on the napkin. All that was left was a pleasant smell. The second thing to evaporate was the water.

Conclusion: I think different liquids have different evaporation rates.

5. This is interesting!

Progress of the experiment:

I applied a thin layer of perfume to the back of my hand. As the perfume evaporated from my hand, I felt cold.

Conclusion: This means that in order to evaporate the liquid, a constant flow of energy from the palm is necessary.

6. This is interesting!

Progress of the experiment:

I wiped one half of the board with a wet, wet rag, and the other with a slightly damp rag. The second half of my board was dry, but the first half was still wet.

Conclusion: This means that the board needs to be wiped with a drier cloth.

Conclusions:

While working on the topic “Evaporation”, I found answers to my questions. I found out why wet laundry dries and water poured on the floor disappears.

The rate of liquid evaporation depends on the free surface area of ​​the liquid. The larger the evaporation area, the faster evaporation occurs.

The rate of evaporation depends on the temperature of the liquid. The higher the temperature of the liquid, the faster evaporation occurs.

The rate of evaporation depends on the movement of air over the free surface of the liquid.

The rate of evaporation depends on the type of liquid taken.

Conclusion

While working on the topic of evaporation, I found answers to my questions. I learned how evaporation occurs, that the rate of evaporation of substances is different. People actively use the evaporation process in their lives, use it in the production of various mechanisms and machines, and use it in everyday life. In nature, this process occurs regardless of human activity, and the task of people is not to disrupt this process. To do this, you need to love nature and love our Earth! The experiments I did were very interesting, and I think there are many more experiments that can be done on this topic. Now I always pay attention to evaporation that occurs in nature or in human life, and I am glad that I already know so much about it!

Annex 1

The process of evaporation in human life.

Evaporation can sometimes be dangerous. For example: if your thermometer breaks, mercury may spill out of it, which quickly evaporates. Its vapors are very dangerous and poisonous to humans. Gasoline is also dangerous due to its vapors: spilling gasoline and an accidental spark can lead to an instant explosion and fire. In the kitchen, the housewife often uses the evaporation process to prepare and preserve food. For example: the steam generated inside a pressure cooker presses on the water, as a result of which it boils at a higher temperature and the food cooks faster.

The evaporation process is often used to sterilize utensils for food preservation.

For colds, people often use the evaporation process when inhaling medicinal herbs.

People can feel the aroma of perfume for a long time only through evaporation; first, alcohol evaporates from the surface of the skin, and then less volatile aromatic substances, which continue to remind of the person even when he has left.

The evaporation process using a hot stream of air allows you to create beautiful hairstyles. A hairdresser's work without a hairdryer is impossible!

Evaporation process in nature

Rivers dissolve many chemicals contained in rocks in their waters and carry them to the sea. One of these substances is ordinary salt, which we eat. When seawater evaporates, the salt dissolved in it remains in the sea. That's why the seas are so salty.

When water droplets in a cloud meet a mass of warm air, they evaporate - and the cloud disappears! Therefore, clouds constantly change their shape. The moisture they contain is constantly converted into water or steam. The water droplets contained in the cloud have weight, so gravity pulls them down and they are released lower and lower. When the main part of them, falling, reaches warmer air layers, this warm air causes them to evaporate. This is how you get clouds from which rain does not fall. They evaporate, and the drops do not have time to reach the earth's surface.