Why does salt water boil faster than fresh water?
Issue resolved and closed.
Where do tears come from? Under the frontal bones of the skull, just above the eye and slightly behind it, is the amygdala lacrimal gland. From this gland, about a dozen lacrimal canals come to the eye and eyelid. When we blink, the lacrimal gland is stimulated and tears flow into the eye. Thus, the eye remains moisturized and clean. Tears are sterile and contain enzymes that destroy bacteria, thereby protecting the eyes from infection.
When we cry, a small percentage of moisture is lost through evaporation, but most of the moisture goes into the inner corner of the eye, flowing down the two lacrimal ducts into the peanut-shaped lacrimal sac, and then into the nasolacrimal duct, where tears are absorbed into the nasal cavity. . Therefore, if you cry a lot, your nose often becomes stuffy.
The baby is not able to produce tears until he is 6-8 weeks old.
Lacrimal fluid contains sodium, calcium and chlorine ions, bicarbonates. To protect the eye from microbes that enter its surface, tears contain lactoferrin, immunoglobulin A, as well as iron, copper, magnesium, calcium, phosphate ions, lactates, citrates, ascorbates and amino acids.
it happens, sometimes I'm drawn to salty, and sometimes I want pipets like sweets :)
you can fry anything, but here's how you like it, xs
http://informacija.lv/ru/uznemeji/veselība-un-skaistumkopšana/tetovēšana/
hangover? lack of potassium .. and minerals in the body ..
Salt water boils at a higher temperature than fresh water, respectively, under the same heating conditions, fresh water will boil faster, salty water will boil later. There is a whole physico-chemical theory why this is the case, "on the fingers" it can be explained as follows. Water molecules bind to salt ions - the process of hydration occurs. The bond between water molecules is weaker than the bond formed as a result of hydration. Therefore, a fresh water molecule is more easily (at a lower temperature) detached from its "environment" - i.e. literally evaporates. And in order for a water molecule with a dissolved salt to “break out of the embrace” of salt and other water molecules, more energy is required, i.e. high temperature. This is simplified, in general, the theory of solutions is a rather abstruse thing.
In one case you are eating to satisfy your hunger, in the other you are gluttony)
Rain water is basically distilled water. But if over the cities there is evaporation from all sorts of chemical plants and landfills, then the rain, having absorbed this "chemistry", becomes chemical itself. For example, if someone burned a tire, sulfur oxide was released. This sulfur oxide, absorbed into the water, becomes sulfurous acid. And this acid will already corrode everything that it gets on, except for glass, of course. But after it corrodes, the remains will be salt. Then the rain will be salty, but after hitting objects.
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:
- 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.
- 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.
- 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.
- 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 of water with salt differs from the usual fresh liquid.
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.
I wrote in Russian that boiling water lie down
No, it's not Russian.
Quote: Vladimir S
Just do not eat all the boiling water in surprise.
A very simple and memorable advice on how to stop confusing these verbs that are similar in meaning forever.
So, the verb "lay down" without a prefix is not used. Therefore, if you desperately need to use it, then feel free to add any prefix that is suitable in meaning and go ahead: put, lay out, lay, shift, fold, etc.
But the verb "put", on the contrary, for some reason does not like prefixes. But on the other hand, he loves when the accent is correctly placed in it: put, put, put (wrong - put), participle put, put participle.
only a chemist can benefit from Google Chemistry
It depends on the individual. You can look into a book and see a fig.
The scale in the kettle is salt, albeit sparingly soluble, i.e. theoretically, water in a kettle with scale will boil at t greater than 100
And you got that the sea is salty, because salted herrings swim in it
Theoretically, in terms of b.b. and b.m. magnitudes, salted herrings thrown into the fresh sea can make it salty. Again, it is necessary to see how many herrings will be.
Without increasing the pressure above one hundred degrees, even Einstein will not heat up.
He won't be able to do this in a laboratory, but an ordinary citizen, in an ordinary kitchen, in an ordinary microwave oven - easily.
And further
And in general, the North was not interested in some kind of boiling centers, but why bonds in hydrated ions
That's exactly what he's not interested in.
Quote: North
If you add salt to the water, it will boil faster.
As we have repeatedly seen above, water without salt can easily be overheated, but it will take more time. If it is salted in advance, then it will take less time, the water will not be overheated, it will boil at 100 ° C.
And despite the fact that water begins to boil at a higher temperature with increasing salt concentration, it theoretically turns out that if you add salt, it will boil earlier. But the examples show that not only theoretically, but also quite practically. And why he said theoretically - because it is still desirable, or even necessary, to take purified water, or even distilled, and the dishes should be clean, smooth.
In an ordinary kitchen, this is not always the case. Usually we boil water as it is, often even from the tap, in ordinary scratched dishes, and salt not for tea, but for soup, that is, other ingredients are present along with salt. There can be no talk of any overheating here. But the questioner didn't provide details.
Boilers are neutral, they do not affect the boiling point.
boiling water falls into the water even before the start of heating
Boilers are a developed rough, spongy, porous surface. We will consider in this capacity the roughness of the surface of the glass bulb.
1. Flask with fresh bidistillate. Everywhere is clean.
2. A flask with a roughness invisible to the eye.
3. A flask with a bottom scratched on the inside with sandpaper.
In all three, the boiling point will be different. boiling, that's what he was talking about. North. Although the temperature boiling in all three cases, of course, will be the same.
By the way, food should be salted after it is ready. I almost not salt. Not after reading Bragg, but since childhood, such are taste preferences.
Many housewives, trying to speed up the cooking process, salt the water immediately after they put the pan on the stove. They firmly believe that they are doing the right thing, and are ready to bring many arguments in their defense. Is this really so and which water boils faster - salty or fresh? To do this, it is not at all necessary to experiment in the laboratory, it is enough to dispel the myths that have reigned in our kitchens for decades, using the laws of physics and chemistry.
Common myths about boiling water
In the matter of boiling water, people can be conditionally divided into two categories. The former are convinced that salt water boils much faster, while the latter absolutely disagree with this statement. In favor of the fact that it takes less time to bring salt water to a boil, the following arguments are given:
- the density of the water in which the salt is dissolved is much higher, so the heat transfer from the burner is greater;
- during dissolution in water, the crystal lattice of table salt is destroyed, which is accompanied by the release of energy. That is, if salt is added to cold water, the liquid will automatically become warmer.
Those who refute the hypothesis that salt water boils faster argue this way: during the dissolution of salt in water, a hydration process occurs.
At the molecular level, stronger bonds are formed that require more energy to break. Therefore, it takes longer for salt water to boil.
Who is right in this dispute, and is it really so important to salt the water at the very beginning of cooking?
The boiling process: physics "on the fingers"
To understand what exactly happens to salt and fresh water when heated, you need to understand what the boiling process is. Regardless of whether water is salty or not, it boils the same way and goes through four stages:
- the formation of small bubbles on the surface;
- an increase in bubbles in volume and their settling at the bottom of the container;
- cloudy water caused by the intense movement of air bubbles up and down;
- the boiling process itself, when large bubbles rise to the surface of the water and burst with noise, releasing steam - the air that is inside and heats up.
The theory of heat transfer, to which supporters of salting water at the beginning of cooking appeal, “works” in this case, but the effect of heating water due to its density and heat release during the destruction of the crystal lattice is insignificant.
Much more important is the process of hydration, in which stable molecular bonds are formed.
The stronger they are, the more difficult it is for the air bubble to rise to the surface and sink to the bottom of the container, it takes more time. As a result, if salt is added to the water, then the circulation of air bubbles slows down. Accordingly, salt water boils more slowly, since molecular bonds hold air bubbles in salt water a little longer than in fresh water.
To salt or not to salt? That's the question
Kitchen disputes about which water boils faster, salted or unsalted, can be endless. As a result, from the point of view of practical application, there is not much difference whether you salted the water at the very beginning or after it boiled. Why doesn't it really matter? To understand the situation, you need to turn to physics, which provides comprehensive answers to this seemingly difficult question.
Everyone knows that at a standard atmospheric pressure of 760 mm Hg, water boils at 100 degrees Celsius. Temperature parameters can change subject to changes in air density - everyone knows that in the mountains water boils at a lower temperature. Therefore, when it comes to the domestic aspect, in this case, such an indicator as the burning intensity of a gas burner or the degree of heating of an electric kitchen surface is much more important.
It is on this that the process of heat transfer depends, that is, the rate of heating of the water itself. And, accordingly, the time spent on it to boil.
For example, on an open fire, if you decide to cook dinner on a fire, the water in the pot will boil in a matter of minutes due to the fact that the wood during combustion emits more heat than the gas in the stove, and the surface heating area is much larger. Therefore, it is not at all necessary to add salt to the water so that it boils faster - just turn on the burner of the stove to the maximum.
The boiling point of salt water is exactly the same as that of fresh water and distilled water. That is, it is 100 degrees at normal atmospheric pressure. But the boiling rate under equal conditions (for example, if the usual gas stove burner is taken as the basis) will differ. Salt water takes longer to boil because it is harder for air bubbles to break the stronger molecular bonds.
By the way, there is a difference in boiling time between tap and distilled water - in the second case, a liquid without impurities and, accordingly, without “heavy” molecular bonds, will heat up faster.
True, the time difference is only a few seconds, which do not make the weather in the kitchen and practically do not affect the speed of cooking. Therefore, one should be guided not by the desire to save time, but by the laws of cooking, which prescribe salting each dish at a certain moment in order to preserve and enhance its taste.
To cook food faster, most housewives add salt to the pan before the water starts to boil. In their opinion, this will speed up the cooking process. Others, on the contrary, argue that tap water boils much faster. To answer this question, you need to turn to the laws of physics and chemistry. Why does salt water boil faster than regular water, and is it really so? Let's find out! Details in the article below.
Why salt water boils faster: physical laws of boiling
In order to understand what processes begin to occur when a liquid is heated, it is necessary to know what scientists mean by the technology of the boiling process.
Any water, ordinary or salty, starts to boil in exactly the same way. This process goes through several stages:
- small bubbles begin to form on the surface;
- an increase in the size of the bubbles;
- their settling to the bottom;
- the liquid becomes cloudy;
- boiling process.
Why does salt water boil faster?
Supporters of salted water say that when heated, the heat transfer theory works. However, the heat released after the destruction of the molecular lattice does not have much effect. Much more important is the technological process of hydration. At this time, strong molecular bonds are formed. So why does salt water boil faster?
When they become very strong, it is much more difficult for air bubbles to move. It takes a long time to move up or down. In other words, if there is salt in the water, the air circulation process slows down. As a result, salt water boils a little slower. Air bubbles are prevented from moving by molecular bonds. That's why it doesn't boil faster than unsalted.
Can you do without salt?
The debate about how fast salt or tap water boils can go on forever. If you look at the practical application, there will not be much difference. This is easily explained by the laws of physics. Water begins to boil when the temperature reaches 100 degrees. This value may change if the air density parameters change. For example, water high in the mountains begins to boil at temperatures below 100 degrees. In domestic conditions, the most important indicator is the power of the gas burner, as well as the heating temperature of the electric stove. The speed of heating the liquid, as well as the time required for boiling, depend on these parameters.
At the fire, the water begins to boil after a few minutes, since the burned firewood emits much more heat than a gas stove, and the area of \u200b\u200bthe heated surface is much larger. From this we can draw a simple conclusion: in order to achieve a quick boil, you need to turn on the gas burner at maximum power, and not add salt.
Any water starts to boil at the same temperature (100 degrees). But the speed of boiling can be different. Salt water will start to boil later because of the air bubbles, which are much more difficult to break molecular bonds. I must say that distilled water boils faster than ordinary tap water. The fact is that in purified, distilled water there are no strong molecular bonds, there are no impurities, so it starts to heat up much faster.
Conclusion
The boiling time of ordinary or salt water differs by several seconds. It has no effect on the speed of cooking. Therefore, you should not try to save time on boiling, it is better to start strictly observing the laws of cooking. To make the dish tasty, it needs to be salted at a certain time. That's why salt water doesn't always boil faster!
