Boiling is the process of changing the aggregate state of a substance. When we talk about water, we mean the change from liquid to vapor. It is important to note that boiling is not evaporation, which can occur even at room temperature. Also, do not confuse with boiling, which is the process of heating water to a certain temperature. Now that we have understood the concepts, we can determine at what temperature water boils.

Process

The very process of transforming the state of aggregation from liquid to gaseous is complex. And although people do not see it, there are 4 stages:

1. In the first stage, small bubbles form at the bottom of the heated container. They can also be seen on the sides or on the surface of the water. They are formed due to the expansion of air bubbles, which are always present in the cracks of the tank, where the water is heated.
2. In the second stage, the volume of the bubbles increases. All of them begin to rush to the surface, as there is saturated steam inside them, which is lighter than water. With an increase in the heating temperature, the pressure of the bubbles increases, and they are pushed to the surface due to the well-known Archimedes force. In this case, you can hear the characteristic sound of boiling, which is formed due to the constant expansion and reduction in the size of the bubbles.
3. In the third stage, a large number of bubbles can be seen on the surface. This initially creates cloudiness in the water. This process is popularly called "boiling with a white key", and it lasts a short period of time.
4. At the fourth stage, the water boils intensively, large bursting bubbles appear on the surface, and splashes may appear. Most often, splashes mean that the liquid has reached its maximum temperature. Steam will start to come out of the water.

It is known that water boils at a temperature of 100 degrees, which is possible only at the fourth stage.

Steam temperature

Steam is one of the states of water. When it enters the air, then, like other gases, it exerts a certain pressure on it. During vaporization, the temperature of steam and water remains constant until the entire liquid changes its state of aggregation. This phenomenon can be explained by the fact that during boiling all the energy is spent on converting water into steam.

At the very beginning of boiling, moist saturated steam is formed, which, after the evaporation of all the liquid, becomes dry. If its temperature begins to exceed the temperature of water, then such steam is superheated, and in terms of its characteristics it will be closer to gas.

Boiling salt water

It is interesting enough to know at what temperature water with a high salt content boils. It is known that it should be higher due to the content of Na+ and Cl- ions in the composition, which occupy an area between water molecules. This chemical composition water with salt is different from ordinary fresh water.

The fact is that in salt water a hydration reaction takes place - the process of attaching water molecules to salt ions. The bond between fresh water molecules is weaker than those formed during hydration, so boiling liquid with dissolved salt will take longer. As the temperature rises, the molecules in water containing salt move faster, but there are fewer of them, which is why collisions between them occur less frequently. As a result, less steam is produced and its pressure is therefore lower than the steam head of fresh water. Therefore, more energy (temperature) is required for full vaporization. On average, to boil one liter of water containing 60 grams of salt, it is necessary to raise the boiling point of water by 10% (that is, by 10 C).

Boiling pressure dependences

It is known that in the mountains, regardless of the chemical composition of water, the boiling point will be lower. This is because the atmospheric pressure is lower at altitude. Normal pressure is considered to be 101.325 kPa. With it, the boiling point of water is 100 degrees Celsius. But if you climb a mountain, where the pressure is on average 40 kPa, then the water will boil there at 75.88 C. But this does not mean that cooking in the mountains will take almost half the time. For heat treatment of products, a certain temperature is needed.

It is believed that at an altitude of 500 meters above sea level, water will boil at 98.3 C, and at an altitude of 3000 meters, the boiling point will be 90 C.

Note that this law also works in the opposite direction. If a liquid is placed in a closed flask through which vapor cannot pass, then as the temperature rises and steam is formed, the pressure in this flask will increase, and boiling at elevated pressure will occur at a higher temperature. For example, at a pressure of 490.3 kPa, the boiling point of water will be 151 C.

Boiling distilled water

Distilled water is purified water without any impurities. It is often used for medical or technical purposes. Given that there are no impurities in such water, it is not used for cooking. It is interesting to note that distilled water boils faster than ordinary fresh water, but the boiling point remains the same - 100 degrees. However, the difference in boiling time will be minimal - only a fraction of a second.

in a teapot

Often people are interested in what temperature water boils in a kettle, since it is these devices that they use to boil liquids. Taking into account the fact that the atmospheric pressure in the apartment is equal to the standard one, and the water used does not contain salts and other impurities that should not be there, then the boiling point will also be standard - 100 degrees. But if the water contains salt, then the boiling point, as we already know, will be higher.

Conclusion

Now you know at what temperature water boils, and how atmospheric pressure and the composition of the liquid affect this process. There is nothing complicated in this, and children receive such information at school. The main thing to remember is that with a decrease in pressure, the boiling point of the liquid also decreases, and with its increase, it also increases.

On the Internet, you can find many different tables that indicate the dependence of the boiling point of a liquid on atmospheric pressure. They are available to everyone and are actively used by schoolchildren, students and even teachers in institutes.

If you leave a container of water uncovered, then after a while the water will evaporate. If you do the same experiment with ethyl alcohol or gasoline, then the process is somewhat faster. If a pot of water is heated on a powerful enough burner, the water will boil.

All these phenomena are a special case of vaporization, the transformation of liquid into vapor. There are two types of vaporization evaporation and boiling.

What is evaporation

Evaporation refers to the formation of vapor from the surface of a liquid. Evaporation can be explained as follows.

During collisions, the velocities of the molecules change. Often there are molecules whose speed is so great that they overcome the attraction of neighboring molecules and break away from the surface of the liquid. (Molecular structure of matter). Since even in a small volume of liquid there are a lot of molecules, such cases are obtained quite often, and there is a constant process of evaporation.

Molecules separated from the surface of the liquid form vapor above it. Some of them, due to chaotic motion, return back to the liquid. Therefore, evaporation occurs faster if there is wind, since it carries the vapor away from the liquid (here, the phenomenon of "capture" and detachment of molecules from the surface of the liquid by the wind also takes place).

Therefore, in a closed vessel, evaporation quickly stops: the number of molecules "torn off" per unit time becomes equal to the number of "returned" into the liquid.

Evaporation rate depends on the type of liquid: the smaller the attraction between the molecules of the liquid, the more intense the evaporation.

The larger the surface area of ​​the liquid, the more molecules have the opportunity to leave it. This means that the rate of evaporation depends on the surface area of ​​the liquid.

As the temperature rises, the speed of the molecules increases. Therefore, the higher the temperature, the more intense the evaporation.

What is boiling

Boiling is intense vaporization, which occurs as a result of heating a liquid, the formation of vapor bubbles in it, floating to the surface and bursting there.

During boiling, the temperature of the liquid remains constant.

The boiling point is the temperature at which a liquid boils. Usually, speaking of the boiling point of a given liquid, they mean the temperature at which this liquid boils at normal atmospheric pressure.

During vaporization, the molecules that have separated from the liquid carry away part of the internal energy from it. Therefore, during evaporation, the liquid is cooled.

Specific heat of vaporization

The physical quantity that characterizes the amount of heat that is required to evaporate a unit mass of a substance is called the specific heat of vaporization. (link for a more detailed discussion of this topic)

In the SI system, the unit of measure for this quantity is J / kg. It is denoted by the letter L.

Everything that surrounds us in everyday life can be represented as physical and chemical processes. We constantly perform a lot of manipulations that are expressed by formulas and equations, without even knowing it. One of these processes is boiling. This is the phenomenon that absolutely all housewives use during cooking. It seems to us absolutely ordinary. But let's look at the boiling process from a scientific point of view.

Boiling - what is it?

Since the school course of physics, it is known that matter can be in a liquid and gaseous state. The process of transforming a liquid into a state of vapor is boiling. This happens only when a certain temperature regime is reached or exceeded. Participates in this process and pressure, it must be taken into account. Each liquid has its own boiling point, which triggers the formation of vapor.

This is the essential difference between boiling and evaporation occurring at any temperature regime of the liquid.

How does boiling happen?

If you have ever boiled water in a glass container, you have observed the formation of bubbles on the walls of the container in the process of heating the liquid. They are formed due to the fact that air accumulates in the microcracks of the dishes, which, when heated, begins to expand. Bubbles are made up of liquid vapor under pressure. These pairs are called saturated. As the liquid heats up, the pressure in the air bubbles increases and they increase in size. Naturally, they begin to rise to the top.

But, if the liquid has not yet reached the boiling point, then in the upper layers the bubbles cool, the pressure decreases and they end up at the bottom of the container, where they heat up again and rise up. This process is familiar to every housewife, as if the water starts to make noise. As soon as the temperature of the liquid in the upper and lower layers is equal, the bubbles begin to rise to the surface and burst - boiling occurs. This is possible only when the pressure inside the bubbles becomes the same as the pressure of the liquid itself.

As we have already mentioned, each liquid has its own temperature regime, at which the boiling process begins. Moreover, during the entire process, the temperature of the substance remains unchanged, all the released energy is spent on vaporization. Therefore, pots burn out at negligent housewives - all their contents boil away and the container itself begins to heat up.

The boiling point is directly proportional to the pressure exerted on the entire liquid, more precisely, on its surface. In the school physics course, it is indicated that water begins to boil at a temperature of one hundred degrees Celsius. But few people remember that this statement is true only under conditions of normal pressure. The norm is considered to be a value of one hundred and one kilopascals. If the pressure is increased, the liquid will boil at a different temperature.

This physical property is used by manufacturers of modern household appliances. An example would be a pressure cooker. All housewives know that in such devices food is cooked much faster than in conventional pans. What is it connected with? With the pressure that is formed in the pressure cooker. It is twice the norm. Therefore, water boils at approximately one hundred and twenty degrees Celsius.

If you have ever been in the mountains, you have seen the reverse process. At a height, water begins to boil at ninety degrees, which greatly complicates the process of cooking. Local residents and climbers who spend all their free time in the mountains are well aware of these difficulties.

A little more about boiling

Many have heard such an expression as "boiling point" and are probably surprised that we did not mention it in the article. In fact, we have already described it. Do not rush to read the text. The fact is that in physics the point and temperature of the boiling process are considered identical.

In the scientific world, separation in this terminology is made only in the case of mixing different liquid substances. In such a situation, it is precisely the boiling point that is determined, and the smallest of all possible. It is she who is taken as the norm for all the constituent parts of the mixture.

Water: interesting facts about physical processes

In laboratory experiments, physicists always take a liquid without impurities and create absolutely ideal external conditions. But in life, everything happens a little differently, because often we add salt to water or add various seasonings to it. What will be the boiling point in this case?

Salt water requires more high temperature for boiling than fresh. This is due to impurities of sodium and chlorine. Their molecules collide with each other, and their heating requires a much higher temperature. There is a certain formula that allows you to calculate the boiling point of salt water. Keep in mind that sixty grams of salt per liter of water increases the boiling point by ten degrees.

Can water boil in a vacuum? Scientists have proven that it can. That's just the boiling point in this case should reach the limit of three hundred degrees Celsius. After all, in a vacuum, the pressure is only four kilopascals.

We all boil water in a kettle, so we are familiar with such an unpleasant phenomenon as "scale". What is it and why is it formed? In fact, everything is simple: fresh water has a different degree of hardness. It is determined by the amount of impurities in the liquid, most often it contains various salts. In the process of boiling, they are transformed into sediment and in large quantities turn into scale.

Can alcohol boil?

Boiling alcohol is used in the moonshine brewing process and is called distillation. This process directly depends on the amount of water in the alcohol solution. If we take pure ethyl alcohol as a basis, then its boiling point will be close to seventy-eight degrees Celsius.

If you add water to alcohol, the boiling point of the liquid increases. Depending on the concentration of the solution, it will boil in the range from seventy-eight degrees to one hundred degrees Celsius. Naturally, during the boiling process, alcohol will turn into steam in a shorter time interval than water.

BOILING TEMPERATURE
(boiling point) - the temperature at which a liquid turns into vapor (i.e. gas) so intensively that vapor bubbles form in it, which rise to the surface and burst. The rapid formation of bubbles in the entire volume of the liquid is called boiling. In contrast to simple evaporation during boiling, the liquid passes into vapor not only from the free surface, but also throughout the entire volume - inside the bubbles formed. The boiling point of any liquid is constant at a given atmospheric or other external pressure, but increases with increasing pressure and decreases with decreasing pressure. For example, at normal atmospheric pressure of 100 kPa (this is the pressure at sea level), the boiling point of water is 100 ° C. At an altitude of 4000 m above sea level, where the pressure drops to 60 kPa, water boils at about 85 ° C, and it takes longer to cook food in the mountains. For the same reason, food cooks faster in a "pressure cooker": the pressure in it rises, and then the temperature of the boiling water rises.
BOILING POINTS OF SOME SUBSTANCES(at sea level)

Substance __ Temperature, °С
Gold ___________2600
Silver __________1950
Mercury _____________356.9
Ethylene glycol _____197.2
Sea water ______100.7
Water ______________ 100.0
Isopropyl alcohol 82.3
Ethyl alcohol _____78.3
Methyl alcohol ____64.7
Ether _______________34.6

The boiling point of a substance also depends on the presence of impurities. If a volatile substance is dissolved in a liquid, then the boiling point of the solution decreases. Conversely, if the solution contains a substance less volatile than the solvent, then the boiling point of the solution will be higher than that of a pure liquid.
see also
SOLIDIFICATION TEMPERATURE ;
HEAT ;
LIQUID THEORY.
LITERATURE
Croxton K. Physics of the liquid state. M., 1978 Novikov I.I. Thermodynamics. M., 1984

Collier Encyclopedia. - Open Society. 2000 .

See what "BOILING POINT" is in other dictionaries:

The temperature at which a liquid boils under constant pressure. The boiling point at normal atmospheric pressure (1013.25 hPa, or 760 mm Hg) is called the normal boiling point or boiling point ... Big Encyclopedic Dictionary

BOILING POINT, the temperature at which a substance passes from one state (phase) to another, i.e. from liquid to vapor or gas. The boiling point increases as the external pressure increases and decreases as it decreases. Usually her... ... Scientific and technical encyclopedic dictionary

- (denoted by Tbp, Ts), the temperature of the equilibrium transition of liquid to vapor at DC. ext. pressure. At T. to. the pressure is saturated. steam above the flat surface of the liquid becomes equal to ext. pressure, as a result of which throughout the volume of the liquid ... ... Physical Encyclopedia

- - the temperature at which the liquid under the influence of heating passes from a liquid state to a gaseous state; This boiling point is pressure dependent. Edwart. Dictionary of automotive jargon, 2009 ... Automobile dictionary

The temperature reached by a liquid when bubbling * * * (Source: United Dictionary of Culinary Terms) ... Culinary Dictionary

boiling temperature- - [A.S. Goldberg. English Russian Energy Dictionary. 2006] Topics energy in general EN boiling temperature … Technical Translator's Handbook

Boiling point, boiling point is the temperature at which a liquid boils under constant pressure. The boiling point corresponds to the temperature of saturated vapor above the flat surface of a boiling liquid, since ... Wikipedia

boiling temperature- (Tboil, tboil) temperature of equilibrium transition of liquid into vapor at constant external pressure. At the boiling point, the saturated vapor pressure over a flat liquid surface becomes equal to the external pressure, ... ... Encyclopedic Dictionary of Metallurgy

The temperature at which a liquid boils under constant pressure. The boiling point at normal atmospheric pressure (1013.25 hPa, or 760 mm Hg) is called the normal boiling point or boiling point. * * … encyclopedic Dictionary

boiling temperature- 2.17 boiling point temperature of a liquid boiling at an ambient atmospheric pressure of 101.3 kPa (760 mmHg). Source: GOST R 51330.9 99: Explosion-proof electrical equipment. Part 10. Classification of hazardous areas ... Dictionary-reference book of terms of normative and technical documentation

Books

• , Yu. A. Lebedev, A. N. Kizin, T. S. Papina, I. Sh. Saifullin, Yu. E. Moshkin. This book presents the most important numerical characteristics of a number of hydrocarbons, among which the following physicochemical constants are considered: molecular weight, temperature ...
• Characteristics of hydrocarbons. Analysis of numerical data and their recommended values. Reference publication, Lebedev Yu.A. This book presents the most important numerical characteristics of a number of hydrocarbons, among which the following physicochemical constants are considered: molecular weight, temperature ...

In the section on the question What is the boiling point of a liquid called? given by the author Kosovorotka the best answer is boiling point of a liquid
Anna
Thinker
(8819)
What is not clear??? Boiling temperature. At what temperature does the liquid boil, brainwashed manenko !!!

Answer from flush[newbie]
(boiling point) - the temperature at which the liquid turns into vapor (i.e., gas) so intensively that steam bubbles form in it, which rise to the surface and burst. The rapid formation of bubbles in the entire volume of the liquid is called boiling. In contrast to simple evaporation during boiling, the liquid passes into vapor not only from the free surface, but also throughout the entire volume - inside the bubbles formed. The boiling point of any liquid is constant at a given atmospheric or other external pressure, but increases with increasing pressure and decreases with decreasing pressure. For example, at normal atmospheric pressure of 100 kPa (this is the pressure at sea level), the boiling point of water is 100 ° C. At an altitude of 4000 m above sea level, where the pressure drops to 60 kPa, water boils at about 85 ° C, and it takes longer to cook food in the mountains. For the same reason, food cooks faster in a "pressure cooker" pan: the pressure in it rises, and after that the temperature of boiling water also rises.

Answer from push through[newbie]
the temperature at which a liquid turns into a gas