Curing time. Lesson topic: “Specific heat of fusion

Many novice builders are familiar with the inevitable appearance of defects on the surface of concrete: small cracks, chips, rapid failure of the coating. The reason is not only non-compliance with concreting rules, or the creation of a cement mortar with an incorrect ratio of components; more often, the problem lies in the lack of care for the concrete during the hardening stage.

The setting time of the cement mortar depends on numerous factors: temperature, humidity, wind, exposure to direct sun rays etc. It is important to moisten the concrete during the hardening stage, this will ensure maximum strength and integrity of the coating.

The setting time of cement mortar depends on numerous factors

General information

Depending on the temperature at which the cement hardens, the hardening period also differs. Best Temperature- 20°C. Under ideal conditions, the process takes 28 days. In hot regions or during cold periods of the year, ensure given temperature difficult or impossible.

In winter, concreting is required for a number of reasons:

laying the foundation for a building located on crumbling soils. During the warm period of the year it is impossible to carry out construction;
In winter, manufacturers make discounts on cement. Sometimes you can really save a lot on material, but storing it until it gets warmer is an undesirable solution, because the quality of the cement will decrease. Pouring concrete on the interior surfaces of buildings and even exterior work in winter is quite appropriate if discounts are available;
private concreting work;
In winter there is more free time and it is easier to take a vacation.

The disadvantage of working in cold weather is the difficulty of digging a trench and the need to equip a heating area for workers. Taking into account additional costs, savings do not always occur.

Features of pouring concrete at low temperatures

The hardening time of the cement mortar depends on the temperature. At low temperatures, the time increases significantly. In the construction industry, it is customary to call the weather cold when the thermometer drops to an average of 4°C. To successfully use cement in cold weather, it is important to take protective measures to prevent the mortar from freezing.

Features of pouring concrete when low temperatures Oh

The setting of concrete at low temperatures proceeds somewhat differently, highest value The final result is affected by the temperature of the water. The warmer the liquid, the faster the process proceeds. Ideally, for winter it is worth ensuring the thermometer reading is at 7-15°. Even in conditions of heated water, the surrounding cold slows down the rate of hydration of the cement mortar. It takes longer to gain strength and set.

To calculate how long cement hardens, it is important to take into account the fact that a drop in temperature by 10° leads to a 2-fold decrease in the hardening rate. It is important to carry out calculations, since premature removal of formwork or use of concrete can lead to destruction of the material. If the ambient temperature drops to -4°C and there are no additives, insulation or heating, the solution will crystallize and the cement hydration process will stop. The final product will lose 50% of its strength. The hardening time will increase by 6-8 times.

Despite the fact that it is necessary to determine how long the concrete hardens, and it is necessary to control the hardening process, there is reverse side– opportunity to improve the quality of the result. Reducing the temperature increases the strength of concrete, but only to the critical level of -4°C, although the procedure takes more time.

Factors affecting hardening

At the planning stage of work with cement, an important factor influencing the final result is the rate of concrete dewatering. The hydration process is influenced by numerous factors; it is possible to more accurately determine how long the cement mortar hardens by taking into account the following factors:

environment. Humidity and air temperature are taken into account. In high dryness and heat, concrete will harden in just 2-3 days, but it will not have time to acquire the expected strength. Otherwise, it will remain wet for 40 days or more;

Factors influencing concrete hardening

filling density. As the cement compacts, the rate of moisture release decreases, this improves the hydration procedure, but slightly reduces the speed. It is better to compact the material using a vibrating plate, but manually piercing the solution is also suitable. If the composition is dense, it will be difficult to process after hardening. At the stage of finishing or laying communications in compacted concrete, it is necessary to use diamond drilling, since pobedit drills quickly wear out;
composition of the solution. The factor is quite important, because the level of porosity of the filler affects the rate of dehydration. The solution with expanded clay and slag hardens more slowly, moisture accumulates in the filler, and it is released slowly. With gravel or sand, the composition dries faster;
presence of additives. Special additives with moisture-retaining properties help to reduce or accelerate the stages of hardening of the solution: soap solution, bentonite, antifreeze additives. The purchase of such components increases the amount of work, but many additives simplify the work with the composition and increase the quality of the result;
formwork material. The hardening time of cement depends on the tendency of the formwork to absorb or retain moisture. The speed of hardening is affected by porous walls: unsanded boards, plastic with through holes or loose installation. The best way complete construction work on time and maintaining technical characteristics concrete - use metal panels or install plastic film on top of the board formwork.

The type of base also influences how long the cement mortar hardens. Dry soil quickly absorbs moisture. When concrete hardens in the sun, the hardening time increases significantly; to prevent the material from obtaining low strength, the surface should be constantly moistened and the area shaded.

Artificially increasing the rate of hardening

The hardening time of cement mortar in cold weather increases greatly, but the time frame still remains limited. To speed up the procedure, various techniques have been developed.

BITUMAST Anti-frost additive for concrete

In modern construction, drying time can be accelerated by:

adding additives;
electric heating;
increasing the required proportions of cement.

Using Modifiers

The easiest way to complete work on time even in winter is to use modifiers. When a certain proportion is added, the hydration period is reduced; when using some additives, hardening occurs even at -30°C.

Conventionally, additives that affect the rate of hardening are divided into several groups:

type C – drying accelerators;
type E – water-substituting additives with accelerated hardening.

The foundation hardening calculator and reviews show maximum effectiveness when potassium chloride is added to the solution. The material is consumed economically, since it is mass fraction up to 2%.

If you use type C concrete curing mixtures, you should take care of heating, since they do not protect against freezing.

Plasticizers and additives for concrete

It is recommended to take care of laying communications in the foundation or screed in advance, otherwise drilling holes will be required. Making communication holes after hardening will lead to the need for a special tool and. The procedure is quite labor-intensive and reduces the strength of the structure.

Concrete heating

Mainly to heat the composition, a special cable is used, which converts electric current in the warmth. The technique provides the most natural way solidification. An important factor It is necessary to follow the instructions for installing the wire. The method protects against liquid crystallization; there are also tools (hair dryer, welding machine) and thermal insulation for frost protection.

Increasing cement dosage

Increasing the cement concentration is used only with a slight decrease in temperature. It is important to increase the dosage in small quantity, otherwise quality and durability will be significantly reduced.

Concrete is a multifunctional composition from which any structure can be built. In modern construction, a variety of cement compositions and methods of processing are used:

The first stage of building construction is drawing up a diagram and calculating the load. Strength depends on various characteristics. It is important to follow all masonry rules to obtain design strength;

common in private construction. They improve thermal insulation properties, reduce the load on the foundation, and make it easy and quick to lay walls. You can make them yourself. are formed using a similar algorithm with blocks;
in wet areas there is a need for additional protection of concrete. A special one is used, since standard mixtures do not completely cover the concrete wall;
One of the most popular and frequent procedures for working with mortar is screeding. The proportions of cement and sand for the screed differ depending on the task at hand.

Conclusion

Concreting in hot or cold conditions requires special measures. If you create ideal conditions for hydration of concrete, it will acquire high strength, will be able to withstand significant load-bearing loads and will become resistant to destruction. The main task of the builder is to prevent freezing or premature drying of the mortar.

To effectively plan all construction work, you need to know how long it takes for concrete to harden. And here there are a number of subtleties that largely determine the quality of the constructed structure. Below we will describe in detail how the solution is dried and what you need to pay attention to when organizing related operations.

To make the material reliable, it is important to properly organize its drying

Theory of polymerization of cement mortar

To manage the process, it is very important to understand exactly how it happens. That is why it is worth studying in advance what hardening of cement is (find out here how to make flowerpots from concrete).

In fact, this process is multi-stage. It includes both strength building and drying itself.

Let's look at these stages in more detail:

Hardening of concrete and other cement-based mortars begins with the so-called setting. In this case, the substance in the formwork enters into a primary reaction with water, due to which it begins to acquire a certain structure and mechanical strength.
Setting time depends on many factors. If we take the air temperature of 200C as a standard, then for the M200 solution the process starts approximately two hours after pouring and lasts about an hour and a half.
After setting, the concrete hardens. Here the bulk of the cement granules react with water (for this reason the process is sometimes called cement hydration). Optimal conditions for hydration is air humidity of about 75% and temperature from 15 to 200C.
At temperatures below 100C there is a risk that the material will not reach its design strength, which is why to work in winter period you need to use special anti-frost additives.

Strengthening schedule

The strength of the finished structure and the rate of hardening of the solution are interrelated. If the composition loses water too quickly, then not all the cement will have time to react, and pockets of low density will form inside the structure, which can become a source of cracks and other defects.

Pay attention! Cutting reinforced concrete with diamond wheels after polymerization often clearly demonstrates the heterogeneous structure of slabs poured and dried in violation of technology.

Photo of a cut with clearly visible defects

Ideally, the solution requires 28 days before complete hardening.. However, if the structure does not have too strict requirements for load-bearing capacity, then you can begin to operate it within three to four days after pouring.

When planning construction or repair work, it is important to correctly assess all the factors that will influence the rate of dehydration of the solution (read also the article “Non-autoclaved aerated concrete and its features”).

Experts highlight the following points:

Vibratory compaction process

Firstly, the most important role is played by conditions environment. Depending on the temperature and humidity, the poured foundation can either dry out in just a few days (and then will not reach its design strength), or remain wet for more than a month.
Secondly – packing density. The denser the material, the slower it loses moisture, which means that the hydration of cement occurs more efficiently. Vibration treatment is most often used for compaction, but when doing the work yourself, you can get by with bayoneting.

Advice! The denser the material, the more difficult it is to process it after hardening. This is why structures that were constructed using vibration compaction most often require diamond drilling of holes in concrete: conventional drills wear out too quickly.

The composition of the material also affects the speed of the process. Mainly, the rate of dehydration depends on the porosity of the filler: expanded clay and slag accumulate microscopic particles of moisture and release them much more slowly than sand or gravel.
Also to slow down drying and more effective recruitment water-retaining additives (bentonite, soap solutions, etc.) are widely used to increase strength. Of course, the price of the structure increases, but you don’t need to worry about premature drying out.

Modifier for concrete

In addition to all of the above, the instructions recommend paying attention to the formwork material. The porous walls of unedged boards draw a significant amount of liquid from the edge areas. Therefore, to ensure strength, it is better to use formwork made of metal panels or lay polyethylene film inside the wooden box.

Porous formwork actively “pulls” moisture from the material

Tips for organizing the process

Self-pouring of concrete foundations and floors must be carried out according to a certain algorithm.

To retain moisture in the thickness of the material and promote maximum strength gain, you need to act like this:

To begin with, we perform high-quality waterproofing of the formwork. To do this, we cover the wooden walls with polyethylene or use special plastic collapsible panels.
We introduce modifiers into the solution, the effect of which is aimed at reducing the rate of evaporation of the liquid. You can also use additives that allow the material to gain strength faster, but they are quite expensive, which is why they are used mainly in multi-story construction.
Then pour the concrete, compacting it thoroughly. For this purpose, it is best to use a special vibrating tool. If there is no such device, we process the poured mass with a shovel or metal rod, removing air bubbles.

The less moisture leaves in the first days, the stronger the base will be.

After setting, cover the surface of the solution with plastic wrap. This is done in order to reduce moisture loss in the first few days after installation.

Pay attention! In autumn, polyethylene also protects cement located in the open air from precipitation, which erodes the surface layer.

After about 7-10 days, the formwork can be dismantled. After dismantling, we carefully inspect the walls of the structure: if they are wet, then you can leave them open, but if they are dry, it is better to also cover them with polyethylene.
After this, every two to three days we remove the film and inspect the concrete surface. When large quantity dust, cracks or peeling of the material, we moisten the frozen solution with a hose and cover it again with polyethylene.
On the twentieth day, remove the film and continue drying naturally.
After 28 days have passed since the filling, the next stage of work can begin. At the same time, if we did everything correctly, the structure can be loaded “to its fullest” - its strength will be maximum!

Knowing how long it takes for a concrete foundation to harden, we will be able to properly organize all other construction work. However, this process cannot be accelerated, since cement acquires the necessary performance characteristics only when it hardens for a sufficient time (also find out how to build a concrete cellar).

More detailed information By this issue outlined in the video in this article.

Theory of polymerization of cement mortar

To manage the process, it is very important to understand exactly how it happens. That is why it is worth studying in advance what hardening of cement is ().

In fact, this process is multi-stage. It includes both strength building and drying itself.

Let's look at these stages in more detail:

Hardening of concrete and other cement-based mortars begins with the so-called setting. In this case, the substance in the formwork enters into a primary reaction with water, due to which it begins to acquire a certain structure and mechanical strength.
Setting time depends on many factors. If we take the air temperature of 20 0 C as a standard, then for the M200 solution the process starts approximately two hours after pouring and lasts about an hour and a half.
After setting, the concrete hardens. Here the bulk of the cement granules react with water (for this reason the process is sometimes called cement hydration). Optimal conditions for hydration are air humidity of about 75% and temperature from 15 to 20 0 C.
At temperatures below 10 0 C, there is a risk that the material will not reach its design strength, which is why special anti-frost additives must be used for work in winter.

The strength of the finished structure and the rate of hardening of the solution are interrelated. If the composition loses water too quickly, then not all the cement will have time to react, and pockets of low density will form inside the structure, which can become a source of cracks and other defects.

Pay attention! Cutting reinforced concrete with diamond wheels after polymerization often clearly demonstrates the heterogeneous structure of slabs poured and dried in violation of technology.

Ideally, the solution requires 28 days before complete hardening.. However, if the structure does not have too strict requirements for load-bearing capacity, then you can begin to operate it within three to four days after pouring.

Factors affecting hardening

When planning construction or repair work, it is important to correctly assess all the factors that will influence the rate of dehydration of the solution ().

Experts highlight the following points:

Firstly, environmental conditions play a crucial role. Depending on the temperature and humidity, the poured foundation can either dry out in just a few days (and then will not reach its design strength), or remain wet for more than a month.
Secondly – packing density. The denser the material, the slower it loses moisture, which means that the hydration of cement occurs more efficiently. Vibration treatment is most often used for compaction, but when doing the work yourself, you can get by with bayoneting.

Advice! The denser the material, the more difficult it is to process it after hardening. This is why structures that were constructed using vibration compaction most often require diamond drilling of holes in concrete: conventional drills wear out too quickly.

The composition of the material also affects the speed of the process. Mainly, the rate of dehydration depends on the porosity of the filler: expanded clay and slag accumulate microscopic particles of moisture and release them much more slowly than sand or gravel.
Also, to slow down drying and more effectively gain strength, moisture-retaining additives (bentonite, soap solutions, etc.) are widely used. Of course, the price of the structure increases, but you don’t need to worry about premature drying out.

In addition to all of the above, the instructions recommend paying attention to the formwork material. The porous walls of unedged boards draw a significant amount of liquid from the edge areas. Therefore, to ensure strength, it is better to use formwork made of metal panels or lay polyethylene film inside the wooden box.

Self-pouring of concrete foundations and floors must be carried out according to a certain algorithm.

To retain moisture in the thickness of the material and promote maximum strength gain, you need to act like this:

To begin with, we perform high-quality waterproofing of the formwork. To do this, we cover the wooden walls with polyethylene or use special plastic collapsible panels.
We introduce modifiers into the solution, the effect of which is aimed at reducing the rate of evaporation of the liquid. You can also use additives that allow the material to gain strength faster, but they are quite expensive, which is why they are used mainly in multi-story construction.
Then pour the concrete, compacting it thoroughly. For this purpose, it is best to use a special vibrating tool. If there is no such device, we process the poured mass with a shovel or metal rod, removing air bubbles.

After setting, cover the surface of the solution with plastic wrap. This is done in order to reduce moisture loss in the first few days after installation.

Pay attention! In autumn, polyethylene also protects cement located in the open air from precipitation, which erodes the surface layer.

After about 7-10 days, the formwork can be dismantled. After dismantling, we carefully inspect the walls of the structure: if they are wet, then you can leave them open, but if they are dry, it is better to also cover them with polyethylene.
After this, every two to three days we remove the film and inspect the concrete surface. If a large amount of dust, cracks or peeling of the material appears, we moisten the frozen solution with a hose and cover it again with polyethylene.
On the twentieth day, remove the film and continue drying naturally.
After 28 days have passed since the filling, the next stage of work can begin. At the same time, if we did everything correctly, the structure can be loaded “to its fullest” - its strength will be maximum!

Conclusion

More detailed information on this issue is presented in the video in this article.

As the temperature decreases, a substance can change from a liquid to a solid state.

This process is called solidification or crystallization.
When a substance solidifies, the same amount of heat is released, which is absorbed when it melts.

The calculation formulas for the amount of heat during melting and crystallization are the same.

The melting and solidification temperatures of the same substance, if the pressure does not change, are the same.
Throughout the entire crystallization process, the temperature of the substance does not change, and it can simultaneously exist in both liquid and solid states.

LOOK AT THE BOOKSHELF

INTERESTING ABOUT CRYSTALLIZATION

Colored ice?

If you add a little paint or tea leaves to a plastic glass of water, stir and, having obtained a colored solution, wrap the glass on top and expose it to frost, then a layer of ice will begin to form from the bottom to the surface. However, don't expect to get colorful ice!

Where the water began to freeze, there will be an absolutely transparent layer of ice. Its upper part will be colored, and even stronger than the original solution. If the concentration of paint was very high, then a puddle of its solution may remain on the surface of the ice.
The fact is that transparent fresh ice forms in solutions of paint and salts, because... growing crystals displace any extraneous atoms and impurity molecules, trying to build an ideal lattice as long as possible. Only when the impurities have nowhere to go does the ice begin to incorporate them into its structure or leave them in the form of capsules with concentrated liquid. Therefore, sea ice is fresh, and even the dirtiest puddles are covered with transparent and clean ice.

At what temperature does water freeze?

Is it always at zero degrees?
But if you pour boiled water into an absolutely clean and dry glass and place it outside the window in the cold at a temperature of minus 2-5 degrees C, covering it with clean glass and protecting it from direct sunlight, then after a few hours the contents of the glass will cool below zero, but will remain liquid.
If you then open a glass and throw a piece of ice or snow or even just dust into the water, then literally before your eyes the water will instantly freeze, sprouting long crystals throughout the entire volume.

Why?
The transformation of a liquid into a crystal occurs primarily on impurities and inhomogeneities - dust particles, air bubbles, irregularities on the walls of the vessel. Pure water has no centers of crystallization, and it can become supercooled while remaining liquid. In this way it was possible to bring the water temperature to minus 70°C.

How does this happen in nature?

In late autumn, very clean rivers and streams begin to freeze from the bottom. Through the layer of clean water it is clearly visible that the algae and driftwood at the bottom are overgrown with a loose coat of ice. At some point, this bottom ice floats up, and the surface of the water instantly becomes bound by an ice crust.

Temperature upper layers water is lower than deep water, and freezing seems to begin from the surface. However clean water freezes reluctantly, and ice primarily forms where there is a suspension of silt and a hard surface - near the bottom.

Downstream from waterfalls and dam spillways, a spongy mass of inland ice often appears, growing in the foaming water. Rising to the surface, it sometimes clogs the entire riverbed, forming so-called jams, which can even dam the river.

Why is ice lighter than water?

Inside the ice there are many pores and spaces filled with air, but this is not the reason that can explain the fact that ice is lighter than water. Ice and without microscopic pores
still has a density less than that of water. It's all about the features internal structure ice. In an ice crystal, water molecules are located at the nodes of the crystal lattice so that each has four “neighbors.”

Water, on the other hand, does not have a crystalline structure, and the molecules in the liquid are located closer together than in the crystal, i.e. water is denser than ice.
At first, when ice melts, the released molecules still retain the structure of the crystal lattice, and the density of water remains low, but gradually the crystal lattice is destroyed, and the density of water increases.
At a temperature of + 4°C, the density of water reaches a maximum, and then begins to decrease with increasing temperature due to an increase in the speed of thermal movement of molecules.

How does a puddle freeze?

When cooling, the upper layers of water become denser and sink down. Their place is taken by denser water. This mixing occurs until the water temperature drops to +4 degrees Celsius. At this temperature, the density of water is maximum.
With a further decrease in temperature, the upper layers of water can become more compressed, and gradually cooling to 0 degrees, the water begins to freeze.

In autumn, the air temperature at night and during the day is very different, so the ice freezes in layers.
The bottom surface of ice on a freezing puddle is very similar to a cross section of a tree trunk:
concentric rings are visible. The width of the ice rings can be used to judge the weather. Usually the puddle begins to freeze from the edges, because... there is less depth there. The area of the resulting rings decreases as they approach the center.

INTERESTING

That in the pipes of the underground part of buildings, water often freezes not in frost, but in thaw!
This is due to poor thermal conductivity of the soil. Heat passes through the ground so slowly that the minimum temperature in the soil occurs later than at the surface of the earth. The deeper, the greater the delay. Often during frosts the soil does not have time to cool, and only when a thaw sets in on the ground does frost reach underground.

That when water freezes in a sealed bottle, it breaks it. What happens to a glass if you freeze water in it? When water freezes, it will expand not only upward, but also to the sides, and the glass will shrink. This will still lead to the destruction of the glass!

DID YOU KNOW

There is a known case when the contents of a well-chilled bottle of Narzan in the freezer, opened on a hot summer day, instantly turned into a piece of ice.

The metal “cast iron” behaves interestingly, which expands during crystallization. This allows it to be used as a material for the artistic casting of thin lace lattices and small tabletop sculptures. After all, when it hardens, expanding, cast iron fills everything, even the thinnest details of the mold.

In Kuban they cook in winter strong drinks- “frost”. To do this, the wine is exposed to frost. The water freezes first, but what remains is concentrated solution alcohol It is drained and the operation is repeated until the desired strength is achieved. The higher the alcohol concentration, the lower the freezing point.

The largest hailstone recorded by humans fell in Kansas, USA. Its weight was almost 700 grams.

Oxygen in a gaseous state at a temperature of minus 183 degrees C turns into a liquid, and at a temperature of minus 218.6 degrees C it turns into a liquid solid oxygen

In the old days, people used ice to store food. Carl von Linde created the first home refrigerator, powered by a steam engine that pumped freon gas through pipes. Behind the refrigerator, the gas in the pipes condensed and turned into liquid. Inside the refrigerator, liquid freon evaporated and its temperature dropped sharply, cooling the refrigerator compartment. Only in 1923, Swedish inventors Balzen von Platen and Karl Muntens created the first electric refrigerator, in which freon turns from a liquid into a gas and takes heat from the air in the refrigerator.

THIS IS YES

Several pieces of dry ice thrown into burning gasoline extinguish the fire.
There is ice that would burn your fingers if you could touch it. It is obtained under very high pressure, at which water turns into a solid state at a temperature well above 0 degrees Celsius.

Any element can be in several different states, subject to some external conditions . Melting and solidification crystalline bodies– major changes in the structure of materials. A good example is water, which can exist in liquid, gaseous and solid states. These different shapes are called aggregate states (from the Greek “I bind”) states. The state of aggregation is the forms of one element, differing in the nature of the arrangement of particles (atoms), which do not change their structure.

How changes happen

There are several processes that characterize changing forms different substances:

hardening;
boiling;
(from solid form immediately to gaseous);
evaporation;
fuse;
condensation;
desublimation (reverse transition from sublimation).

Each transformation is characterized by certain conditions that must be met for a successful transition.

Formulas

What process is called thermal? Any where there is a change states of aggregation materials, since temperature plays a big role in them. Any thermal change has its opposite: from liquid to solid and vice versa, from solid to vapor and vice versa.

Important! Almost everything thermal processes reversible.

There are formulas that can be used to determine what the specific heat will be, that is, the heat required to change 1 kg of solid.

For example, the formula for solidification and melting is: Q=λm, where λ is the specific heat.

But the formula for displaying the cooling and heating process is Q=cmt, where c – specific heat is the volume of heat to heat 1 kg of material by one degree, m is the mass, and t is the temperature difference.

Formula for condensation and vaporization: Q=Lm, where specific heat is L, and m is mass.

Description of processes

Melting is one of the ways to deform a structure, translation from solid state into liquid. It proceeds almost the same in all cases, but in two different ways:

the element is heated externally;
heating occurs from the inside.

These two methods differ in tools: in the first case, substances are heated in a special furnace, and in the second, current is passed through the object or it is inductively heated by placing it in an electromagnetic field with high frequencies.

Important! The destruction of the crystalline structure of the material and the occurrence of changes in it leads to the liquid state of the element.

Using different tools you can achieve the same process:

temperature rises;
the crystal lattice changes;
particles move away from each other;
other disturbances of the crystal lattice appear;
interatomic bonds are broken;
a quasi-liquid layer is formed.

As has already become clear, temperature is the main factor due to which the state of the element changes. The melting point is divided into:

light - no more than 600°C;
medium - 600-1600°C;
tight – over 1600°C.

The tool for this work is chosen according to its membership in one group or another: the more the material needs to be heated, the more powerful the mechanism should be.

However, you should be careful and check the data with the coordinate system, for example, the critical temperature of solid mercury is -39°C, and that of solid alcohol is -114°C, but the larger of them will be -39°C, since according to the coordinate system this is the number closer to zero.

No less important indicator is also the boiling point, at which liquid boils. This value is equal to the heat of vapor formed above the surface. This indicator is directly proportional to pressure: as pressure increases, the melting point increases and vice versa.

Auxiliary materials

Each material has its own temperature indicators at which its shape changes, and for each of them you can create your own melting and solidification schedule. Depending on the crystal lattice, the indicators will vary. For example, ice melting graph shows that it requires very little heat, as shown below:

The graph shows the relationship between the amount of heat (vertical) and time (horizontal) required to melt ice.

The table shows the quantities needed to melt the most common metals.

A melting chart and other auxiliary materials are extremely necessary during experiments in order to track changes in the position of particles and notice the beginning of changes in the shape of elements.

Solidification of bodies

Hardening is changing the liquid form of an element into a solid one. A necessary condition is a decrease in temperature below freezing point. During this procedure, a crystalline structure of molecules can be formed, and then the change in state is called crystallization. In this case, the element in liquid form must cool to the temperature of solidification or crystallization.

Melting and solidification of crystalline bodies occurs under the same conditions external environment: crystallizes at 0 °C, and ice melts at the same temperature.

And in the case of metals: iron required 1539°C for melting and crystallization.

Experience proves that in order for a substance to solidify, it must release an equal amount of heat as during the reverse transformation.

The molecules are attracted to each other, forming crystal lattice, unable to resist as they lose their energy. Thus, specific heat determines how much energy is needed to transform a body into a liquid state and how much of it is released during solidification.

Curing Formula – this is Q = λ*m. During crystallization, a minus sign is added to the Q sign, since the body in this case releases or loses energy.

We study physics - graphs of melting and solidification of substances

Crystal melting and solidification processes

Conclusion

All these indicators of thermal processes must be known for a deep comprehension of physics and understanding of primitive natural processes. It is necessary to explain them to students as early as possible, using available tools as examples.