What seawater consists of: composition in percentage and density. What seawater consists of: composition in percent and density The salt content of seawater is 5
Tasks for mixtures and alloys:
A task. How many kg of salt in 10 kg of salt water, if the percentage of salt is 15%.
Solution. 10 × 0.15 = 1.5 (kg) salt.
Answer: 1.5 kg.
The percentage of a substance in a solution (for example, 15%) is sometimes called a% solution, for example, a 15% salt solution.
A task. The alloy contains 10 kg of tin and 15 kg of zinc. What is the percentage of tin and zinc in the alloy?
Solution: The percentage of a substance in an alloy is the fraction that constitutes the weight of a given substance relative to the weight of the entire alloy.
1) 10 + 15 = 25 (kg) - alloy;
2) 10/25. 100% = 40% - the percentage of tin in the alloy;
3) 15/25. 100% = 60% - the percentage of zinc in the alloy;
Answer: 40%, 60%.
A task... Sea water contains 8% salt. How many kilograms fresh water must be added to 30 kg of seawater so that the salt content in the latter is 5%.
Solution: Salt is a pure substance and sea water is a solution.
When fresh water is added to seawater, the content of the pure substance does not change. Let fresh water - x kg.
We make the equation: 0.05 × (30 + x) = 0.08 × 30.
We get x = 18. 18 kg of fresh water must be added. Answer: 18 kg.
A task. Alloy of tin with copper weighing 12 kg contains 45% copper. How much pure tin must be added to obtain an alloy containing 40% copper?
Solution: Tin is the purest substance in the alloy. Let x kg of tin be added to the alloy. At the same time, the pure substance remains unchanged.
We make the equation: 0.4 × (12 + x) = 12 × 0.45.
We get x = 1.5. 1.5 kg of tin must be added. Answer: 1.5 kg.
When solving the following tasks, it is necessary to establish control over the amount of this substance and its concentration at each refill, as well as at each topping up of the mixture. As a result of such control, we obtain a resolving equation.
Example. The concentration of silver in the alloy 300 g is 87%. This means that pure silver in the alloy is 261 g.
Solution. 300 × 0.87 = 261 (g).
A task. 5 liters of 35% fat cream was mixed with 4 liters of 20% cream and 1 liter of pure water was added to the mixture. What is the fat content of the mixture?
Solution. 0.35 × 5 + 0.2 × 4 = p × (5 + 4 + 1), whence p = 0.255, which is 25.5%
Answer. 25.5%
A task. There are 2 alloys, one of which contains 40% and the other 20% silver. How many kg of the second alloy must be added to the 20 kg of the first in order to get an alloy containing 32% silver after alloying together?
Solution: Suppose that x kg of the second alloy should be added to 20 kg of the first alloy. Then we get (20 + x) kg of a new alloy. 20 kg of the first alloy contains 0.4. 20 = 8 (kg) silver, x kg of the second alloy contains 0.2x kg of silver, and (20 + x) kg of the new alloy contains 0.32. (20 + x) kg of silver. Let's make the equation:
8 + 0.2x = 0.32. (20 + x); x = 13 1/3.
Answer: 13 1/3 kg of the second alloy must be added to 20 kg of the first to obtain an alloy containing 32% silver.
Solution. Let x L of a 5% salt solution be added. Then the new solution became (15 + x) l, which contained 0.8. (15 + x) L of salt. 15 liters of a 10% solution contains 15. 0.1 = 1.5 (l) salt, x l of a 5% solution contains 0.05x (l) salt.
Let's make an equation.
1.5 + 0.05x = 0.08. (15 + x);
x = 10.
A task. There is a piece of copper-tin alloy with a total weight of 12 kg, containing 45% copper. How much pure tin would have to be added to this piece of alloy to make the new alloy 40% copper?
Let x kg of tin be added to the alloy. Since the percentage of copper in the alloy is 45%, the mass of copper in the original alloy is m = 0.45 × 12 = 5.4 kg (where 0.45 is the concentration of copper in the alloy).
Then 12 + x is the mass of the new alloy
And since the mass of copper in the original alloy is 5.4 kg, then 0.4
- the concentration of copper in the new alloy.
By condition, solving the equation, we get x = 1.5 kg.
Answer: You need to add 1.5 kg of pure tin.
A task. Mixed 500 g of 10% salt solution and 400 g of 55% salt solution. Determine the concentration of salt in the mixture.
Solution:
1) find the absolute salt content in solution I
500· 0.1 = 50g
2) Find the absolute salt content in solution II.
400· 0.55 = 220 g
3) Find the mass of the resulting mixture
500 + 400 = 900 g
4) Find the absolute salt content in the mixture
5) find the concentration of salt in the mixture
270g (absolute salt content)
900 g (total weight) = 0.3 = 30%
So, the salt concentration in a mixture of two initial solutions is 30%
A task. A piece of alloy of copper and tin weighing 36 kg contains 45%.
How much copper do you need to add to this piece to make an alloy containing 60% copper?
1) Find the absolute content of copper in the alloy
36 0.45 = 16.2 kg
2) what you need to know so that the concentration of copper in a new piece is 60%?
the absolute copper content in the new lump after addition and the resulting total mass of the lump.
Then we denote by x - the mass of added copper
3) find the absolute copper content in the new piece: 16.2 + x
4) find the mass of the resulting piece: 36 + x
5) knowing the percentage of copper in the new piece, we will compose the equation.
Solving equation 5 (16.2 + x) = 3 (36 + x)
we get x = 13.5 kg of copper you need to add to the piece to get 60% concentration.
A task. Mixed 20% and 40% hydrochloric acid solutions and received a 25% solution. Find the ratio of the masses of the initial solutions.
Solution: Method 1:
Let us denote by x 1 - the absolute content of acid in solution I
x 2 - absolute acid content in solution II
for m 1 - total mass I of the solution
for m 2 - the total mass of II solution
Then the concentration I of the solution: 0,2 (1)
concentration of II solution: 0.4 (2)
When mixing two solutions, the total mass of the mixture will be equal to m 1 + m 2, and the absolute content of pure acid in the mixture will be x 1 + x 2
Then the percentage of acid in the mixture is 0.25 (3)
express x 1 and x 2 from (1) and (2) equalities, and obtain and substitute in (3)
We get 0.25
0,2m 1 =0,6m 2
What is the originality of this task?
In that we got one equation when solving the problem, and two unknowns!
Method 2:
1 solution 20 40-25=15 3
25
2 solution 40 25-20=5 1
Thus, the ratio of the masses of the initial solutions is 3: 1.
A task. There are two different concentration of sodium chloride solutions. If you merge together 100 g of I solution and 200 g of the second, you get a 50% solution. If you merge 300 g of the first solution and 200 g of the second, you get a 42% solution. Determine the concentration of these solutions.
1) Find the absolute salt content after 100 g of solution I and 200 g of the second have been poured.
(100 + 200) 0.5 = 150 g
2) We find the absolute salt content after we have poured out 300 g of the first solution and 200 g of the second
(300 + 200) 0.42 = 210g
3) we denote by x - the salt concentration in solution I
for y- salt concentration in solution II
then the absolute salt content after mixing I:
after II mixing:
We obtain a system of equations with two unknowns
Solving it, we get x = 0.3 = 30% - salt concentration in solution I
y = 0.6 = 60% - salt concentration in solution II
Answer: 60% - salt concentration in solution II, 30% - salt concentration in solution I
A task. There are two bars containing silver. The percentage of silver in ingot I is 40% less than in ingot II. After both ingots were fused, an ingot containing 36% silver was obtained. Find the mass of I and II ingots, if ingot I contained 6 kg of silver, and in II - 12 kg.
Let the mass of I ingot be x kg, and II - y kg, then 6 / x is the percentage of silver in I ingot, and 12 / y is the percentage of silver in II ingot. Since 12 / y is 40% greater than 6 / x, we can write the equation 12 / y - 6 / x = 0.4
After the pieces were fused, the percentage of silver in the new piece became 36%, i.e. (12 + 6) / (x + y) = 0.36, where 12 + 6 is the absolute silver content and (x + y) is the total mass.
We get the system:
12 / y - 6 / x = 0.4.
(12 + 6) / (x + y) = 0.36
Solving the system, we get:
y 2 - 95y + 1500 = 0
Whence y 1 = 20 kg, y 2 = 75 kg - does not satisfy the condition x + y = 50 kg
Then x = 50-20 = 30kg
So, the mass of I ingot is 30 kg.
Answer: 30 kg, 20 kg.
A task. How many by weight 90% and 60% phosphoric acid solutions should be taken to obtain 5.4 kg of 80% phosphoric acid solution?
Solution:
Let's make a diagonal diagram:
We get:
NS: at= 20: 10 = 2: 1.
This means that a 90% solution of phosphoric acid should be taken 2 times more than a 60% solution, i.e. NS = 2y.
Let's make the equation: 2 y + y= 5,4.
Hence y = 1.8 kg.
Answer. 3.6 kg 90% and 1.8 kg 60%
phosphoric acid solutions.
A task. Two silver ingots were melted: 75 g of the 600th and 150 g of the 864th standard. Determine the sample of the alloy.
Solution
Let the alloy sample be NS.
Let's make a diagonal diagram:
We get:
(864 – NS) : (NS – 600) = 75: 150 = 1: 2;
1728 – 2NS = NS – 600; NS = 776.
Answer. Received alloy 776th test.
A task. Some quantities of 72% and 58% acid solutions were mixed, resulting in a 62% solution of the same acid. If each solution were taken 15 liters more, then a 63.25% solution would be obtained. How many liters of each solution were taken initially to form the first mixture?
Solution
We use the diagonal scheme twice:
We get:
NS : at= 4: 10 = 2: 5.
We get:
(NS + 15) : (y + 15) = 5,25: 8,75 = 3: 5.
Let's compose a system of equations and solve it:
Answer. The first mixture contained 12 liters of 72% solution
and 30 liters of 58% solution.
A task. How many grams of a 9% alcohol solution can be obtained from 200 g of a 70% alcohol solution?
Solution
A 9% alcohol solution is obtained from 70% alcohol by diluting it with water. The water contains 0% alcohol. Let's apply the diagonal scheme:
We get:
NS : at = 63: 9 = 7: 1.
This means that 1 part of a 70% alcohol solution must be diluted with 7 parts of water. Therefore, 200 g of a 70% alcohol solution must be diluted with 200 7 = 1400 g of water.
In total, we get: 200 + 1400 = 1600 g of a 9% alcohol solution.
Answer. From 200 g of 70% alcohol solution you can
get 1 kg 600 g of a 9% alcohol solution.
A task. Two vessels with salt solution are supplied for evaporation. The daily evaporated portions of salt are constant for each vessel. From the first vessel 48 kg of salt was obtained, and from the second, which stood 6 days less - 27 kg. If the first vessel stood for the same number of days as the second, and the second as long as the first, then the same amount of salt would be obtained from both solutions. How many days did each solution stand?
Solution: Let's pay attention to the phrase from the problem: the daily evaporated portions of salt are constant for each vessel.
This must be understood in such a way that the mass of the salt obtained is directly proportional to the number of days of evaporation, while the amount of salt obtained every day is the coefficient of proportionality. That is, we have a functional dependence:
The amount of salt evaporated = evaporation rate * number of days.
Let k 1 be the coefficient of proportionality for the first vessel, k 2 - for the second vessel. x days, the salt was evaporated from the first vessel.
Let's compose and solve the system of equations:
27 = k 2 (x-6),
k 1 (x-6) = k 2 x.
Substitute the obtained values into the third equation of the system
(48 / x) * (x-6) = (27 / (x-6)) * x
Denoting the inverse fractions involved here as t and 1 / t, respectively, we obtain t = 3/4
(x-6) / x = 3/4, x = 24
So, the first vessel stood for 24 days, and the second vessel stood 6 days less, or 18 days.
Before talking about seawater, let's recall a little of what we generally know about water. From school we know that more than two thirds of the earth's surface is covered with water. Most of it is salty water. However, I must say that there is no completely fresh, distilled water in nature, it can only be obtained artificially. Natural waters contain a certain amount of salts. For example, rainwater contains 1 gram of salt per 30 kilograms of water. Of course, we call this water fresh.
The cult of water has long existed among people. Their fantasy settled many gods in the sea, the most powerful of which was Neptune among the Romans, Poseidon among the Greeks. River and rainwater were ruled by other gods. Interestingly, a hundred years ago the peasants on the island of Sicily, after many fruitless appeals to Saint Andrew, the patron saint of water, with a request to make it rain, finally lost patience and decided to hang a statue of the hapless patron saint, announcing briefly: "Rain or rope."
Only three percent of the world's water is fresh, or what we call fresh water. And they are distributed over the land area extremely unevenly. To conserve water, they resort to different methods: they pump clay solutions into the soil to reduce filtration into the soil, cover the surface of reservoirs with special synthetic films, etc. Meanwhile, many arid regions are located near water, albeit salty, sea. For example, the waterless steppe Crimea is surrounded by the sea. And there is not enough water on the southern coast of Crimea. True, the system of hydraulic engineering measures, the construction of which is now being carried out, will make it possible to largely fill this gap in nature, but just here it would be advisable to use also desalinated sea water.
Installations for desalination of seawater are successfully operating in various regions of the Soviet Union and abroad. In the city of Shevchenko on the shores of the Caspian Sea, for example, such an installation provides 450 liters of fresh water per day for each person. Water is desalinated here mainly by evaporation, but other methods are also used, for example, chemical (absorption of salts by ion-exchange resins) and electrochemical (collection of salt ions by electrodes). There is also a question about water desalination in some Far Eastern regions. There it will be beneficial also because the resulting salt can be used for salting fish. Now salt has to be transported to the Far East in trains thousands of kilometers away. It makes sense to use the experience of Japanese specialists who have built a plant for the complex processing of sea water. This plant, when processing 4000 tons of seawater, produces 3000 tons of fresh water, 110 tons of sodium chloride and Glauber's salts, 16 tons of magnesium, 17 tons of chlorine and other substances. Of course, such a comprehensive processing of seawater will be beneficial not only for the regions Of the Far East but also for other coasts that need fresh water.
Let us note a number of common features of water, before moving on to the story about the waters of the Black Sea. It is known, for example, that water has a high heat capacity. When heated, it absorbs a large amount of heat, and when it cools, it emits it. Therefore, coastal areas are usually warmer than areas located at the same geographical latitude, but far from the sea. If on the seashore there are still high mountains that do not allow heat to spread far, then the climate of the coastal regions will be even warmer. Such conditions exist in our Black Sea in the regions of the Soviet subtropics. These are the northernmost subtropics on the globe. Sochi, for example, is located at the latitude of Vladivostok and New York, where the climate is known to be more severe than in Sochi.
Another property of water is that it requires a lot of heat to evaporate. What role does this property play? If evaporation required little heat, then many rivers and lakes would dry up to the bottom in summer.
It is often said that water is the carrier of life, the ocean is the cradle of life. Indeed, the first organisms originated in water and many still live in this nutrient medium. Moving from one region to another and from top to bottom, water carries organic matter and oxygen to feed animals and plants. Where such movements are weakened, for example, in the depths of the Black Sea, life disappears.
The Black Sea is our warmest sea. The water temperature on its surface for six months is higher than 16 degrees, and in summer more than 25 degrees. In winter, the surface of the main part of the sea cools down to 6-8 degrees. The bays in its northwestern part, as a rule, freeze, the winds repeatedly break the ice, forming hummocks up to 3 meters in height. In some years, icebreakers are used in the Odessa region to take ships out to sea.
Sharp fluctuations in temperature occur during surging winds. The drainage of water leads to its cooling, the surge - to the spread of heat inward. In Crimea, once with a strong wind in a few hours, the water temperature dropped by 12 degrees (from 23 to 11).
The temperature of the water in the depth of the sea is distinguished by exceptional constancy: from 200 meters to the very bottom, and in summer and winter the temperature is kept at 8-9 degrees Celsius.
How does sea water differ from river water? Everyone will say: because the sea water is salty. The salinity of water is determined by the number of grams of salt per kilogram of seawater. It is interesting to compare the salinity of water in different seas and the World Ocean;
The number of grams of salt per 1 kilogram of sea water:
| World Ocean | 35 - 36 |
| Mediterranean Sea | 37 - 39 |
| Red sea | 41-60 |
| Black Sea: | |
| Black Sea: on the surface in the main part | 17-18 |
| Black Sea: in the northwestern part | 8-13 |
| Black Sea: at the bottom | 22-22,5 |
| Caspian Sea | 11-13 |
| Azov sea | 9-10 |
The table shows that the salinity of the Black Sea is two times lower than that of ocean waters, but twice the salinity of the Sea of Azov and one and a half times that of the Caspian. Many consider the Caspian Sea to be very salty. This idea is wrong, only the Kara-Bogaz-Gol Bay and a number of smaller bays are very saline. By the way, the most salty of all the seas of the globe, the Dead Sea, located in Palestine, contains up to 300 grams of salt per 1 kilogram of sea water.
Only the Jordan River flows into this sea, and not a single river flows out of it.
The water in this sea is so dense that you cannot drown. You can not only lie, but also sit on the surface of the water. It is said that the Roman emperor Titus ordered rebellious slaves to be fettered and thrown into the Dead Sea. Imagine his amazement when he saw that they were not drowning.
The Dead Sea is named for a different reason. The fact is that there is no life in water of such salinity. There is no life at the depths in the Black Sea either, although the salinity there is low. But we will talk about this later, and now we will dwell on one more important property of sea water.
With a change in salinity, the properties and taste of water change, but there is something in common that unites both the desalinated Black Sea, and the salted Red Sea, and the World Ocean. The fact is that, despite the difference in salinity, the composition of the salts dissolved in sea water is extremely constant. Why? The composition of the salts in the sea is regulated by animals and plants. Even a small fish weighing 100 grams passes 20-30 cubic centimeters of water through itself per minute. And how much water the huge inhabitants of the ocean let through!
It is known that when the primary ocean was formed and there were no animal organisms yet, the composition of the salts of this ocean was different. Now in seawater, basic salts are contained in the following amounts (percent):
In some seas, only small fluctuations in the composition of salts are observed, not exceeding one percent. So, in the Black Sea, in comparison with the World Ocean, contains slightly more calcium carbonate and potassium chloride, but less calcium sulfate.
An insignificant change in the salt composition brings the Black Sea water somewhat closer to the river water (not in terms of salinity, but in terms of the composition of salts).
It is interesting to compare the composition of salts (in percent) of sea and river water.
Thus, chlorides prevail in seawater, and carbonates in river water. In addition, there are much fewer organic compounds in seawater than in river water, since these compounds are absorbed by numerous inhabitants of the sea.
Sodium chloride (table salt) gives the sea water a salty taste, and magnesium chloride and magnesium sulfate (or Epsom salt) give a bitter taste. At present, 60 different elements have been discovered in its composition, but it is assumed that it contains all the elements found on Earth, only some of them have not yet been discovered.
In the form of charged particles - ions in seawater there is iron, copper, tin, zinc, lead. There is also gold, and silver, and radium, and radon, and bromine, and iodine, but many of them are present in very small quantities. For example, there is 1 milligram of silver per ton of seawater, and even less gold. Despite this seemingly insignificant content, if it were possible to extract all the gold from the waters of all the seas and oceans of the globe, then for every inhabitant of the Earth there would be one and a half million rubles in gold!
Gold is obtained from seawater using ion exchangers - ion exchange resins, which are able to attach to themselves the ions of substances dissolved in water. Unfortunately, gold obtained in this way is still very expensive; the cost of energy spent on its production is five times greater than the cost of mined gold.
Sea water is a complex chemical compound. It was formed over millions of years.
Sea water has a number of healing properties... It has an extremely beneficial effect on the human body. When bathing, we feel the coolness, which is especially pleasant on a hot day. Water reduces the weight of a person (remember Archimedes' law?). Most fat people feel at sea easily and freely. Being in the sea, we always make some kind of movement, this leads to increased breathing, metabolism, improved appetite and digestion. Do not be surprised if you tan while swimming, although you were not lying on the beach at all: this was because the surface layer of the sea perfectly transmits ultraviolet rays, which cause tanning of the body. The sea air saturated with oxygen, salts of sodium chloride, calcium, magnesium, iodine, bromine, and the smallest fractions of radioactive substances is extremely useful for humans. Medicine is currently practicing even a special way of treating certain diseases of the pulmonary tract: patients are placed near special fountains that spray moisture around. This method is called hydroaeronization. The sea is a natural hydroaeronizer. Patients with hypertension, bronchial asthma feel relief of breathing by the sea, because the sea has a lot of ozone and oxygen ions. The presence of ozone is also explained by the fact that there are no microbes in the sea air, ozone kills them.
The sea has a beneficial effect on the human nervous system. The measured splash of waves and the rustle of pebbles, the coolness of the water when bathing, have a calming effect. Even the color of the sea and coastal vegetation affects our well-being.
However, the sea and the sun, with excessive use of these potent agents, can turn from your friends into enemies. Do not swim until chills or goose bumps appear. People with shortness of breath should not swim fast. And, of course, only harm can bring a person many hours of "watch" on the beach in pursuit of a bronze skin color.
The healing properties of sea water have long been used by humans. Many people know how sea water is beneficial for gargling with a mild cold. Small wounds quickly heal in the water (of course, you should not enter the water with a large bleeding wound to avoid infection),
Currently, seawater is used as one of the components in the manufacture of a number of medicines, for example, for the treatment of certain eye and ear diseases. Doctors sometimes inject seawater (somewhat diluted and, of course, disinfected) into a person's muscle as a saline solution to support the body's vital functions.
In terms of its hydrological regime, the Black Sea differs sharply from other seas. It has a highly freshened and, therefore, lighter surface layer (in summer it is warm) lies on a denser, salty lower layer. The presence of two layers is constantly supported by the removal of fresh water from rivers and desalinated water from the Sea of Azov, as well as deep (dense) water from the Marmara Sea. The exchange of water between these layers is very weak. What is this water exchange for? First of all and mainly for the distribution of oxygen in depth, for the so-called aeration of the depths. Oxygen is generated in the surface layers of the sea. It spreads inland by means of vertical water exchange. Where there is no vertical movement of water, there is no oxygen in the deep layers. We observe such a case in the Black Sea.
Significant summer overheating of the mass of water contributes to the accumulation of heat for the winter. The large heat reserve of the sea, like any other phenomenon, should be considered multilaterally. It is positive that the sea does not freeze in its main part and that it heats the coast in winter (a climate-forming factor). A negative consequence is that surface, highly heated waters cannot cool down significantly during the short Black Sea winter. Weak winter cooling under the condition of relatively low salinity leads to a very small increase in density and, therefore, to a slight subsidence of surface waters (no more than 200 meters). In the lower layers, stagnant water forms, oxygen does not penetrate there from (The surface of the sea, therefore, there is no life there either.
True, it cannot be said that there is absolutely no exchange of surface waters with deep waters in the Black Sea. The hypothesis of such a water exchange was put forward by Professor V.A.Vodyanitsky and confirmed by other scientists. An indirect proof of the presence of vertical water exchange is that over time, the surface layers of the sea are not desalinated, and the deep ones do not become saline. Soviet scientists also found direct evidence of the presence of water exchange between layers. Its main reasons are the so-called transverse deep currents, capturing layers up to 1000 meters in depth, as well as thermal mixing resulting from the influence of the heat of the earth's crust and as a result of putrefactive processes at the bottom. True, vertical movements in the Black Sea are very weak. It is estimated that a particle of water takes 80 to 430 years to travel from its deepest depths to the surface. Although this is not a short period of time, the very fact of the presence of vertical movement is important here. Therefore, Soviet scientists, of course, could not agree with the proposal of a number of foreign scientists to dump the remnants of atomic production into the Black Sea.
In addition to salts, a significant amount of gases are dissolved in seawater: oxygen, carbon dioxide, hydrogen sulfide, nitrogen and others. The lower the temperature and salinity of the water, the more gases are dissolved.
We have already discussed the role of oxygen dissolved in seawater. Typically, the surface layers of the sea contain 5-10 cubic centimeters of oxygen per liter of water.
The source of hydrogen sulfide is the decomposition of the remains of aquatic organisms. As it was established half a century ago by the outstanding Russian chemist ND Zelinsky, hydrogen sulfide in the Black Sea is of biochemical origin. The scientist showed that special bacteria living in large numbers in the depths of the sea, living in an oxygen-free environment, decompose the corpses of animals and plants into a number of simpler chemical compounds that interact with the salts of sea water. As a result of this reaction, free hydrogen sulfide is formed. In the Black Sea, where water exchange practically takes place down to a depth of 150-200 meters, and “corpses” of plant and animal organisms constantly rain down to the bottom, the hydrogen sulfide content reaches 7.5 cubic centimeters per liter of water, and the total amount of hydrogen sulfide in the Black Sea is one billion tons. Over the past 1-2 thousand years, this number has remained approximately constant. Although the formation of hydrogen sulfide occurs all the time in the depths of the sea, in parallel with it is the process of oxidation of hydrogen sulfide by other bacteria living on the bottom and in the depths of the Black Sea. The bacteria are called great laborers. Their centuries-old work could create entire islands, for example, the Bahamas are made up of calcium carbonate precipitated by bacteria. There are bacteria that eat oil. Oil would have covered all seas and oceans with a film long ago, if not for these bacteria. In the Black Sea, iron bacteria, figuratively speaking, created the Kerch Peninsula. For thousands of years, the rivers carried ferrous iron, bacteria turned it into iron oxide, which now lies in a 20-meter layer of ores on the Kerch Peninsula. There are even bacteria that eat the asphalt. These are not workers, but destroyers.
Sulfur bacteria, the same as in the Black Sea, oxidized hydrogen sulfide in ancient lakes and swamps, turned it into pure sulfur. Subsequently, sulfur deposits formed in the places of these lakes. Now the demand for sulfur is increasing. The developing chemistry requires more and more sulfur for the manufacture of plastics, paints, glass, fertilizers. Over time, the reserves of sulfur can be depleted, so scientists are already working to colonize modern swamps with such bacteria, so that in the future, sulfur reserves will form here. A method of using the Black Sea hydrogen sulphide will also be developed. In addition, the conditions existing at the bottom of the Black Sea are very similar to those in ancient water bodies, where oil was formed during the decomposition of animal remains without access to oxygen. Therefore, if oil is currently being formed at the bottom of the Black Sea, it will be possible to use it in the future.
Hydrogen sulfide in the Black Sea is not the only exception in the world. Hydrogen sulfide is found in significant quantities in some Norwegian fiords, in the deep-water parts of the Caspian Sea and in other areas where vertical water exchange is difficult. In other seas, for one reason or another, the mixing of waters occurs much deeper, often to the bottom. Such reasons can be either autumn-winter cooling of water, or ice formation, or summer evaporation in salt waters. Where there are no large vertical movements of water, its stagnation occurs, and the decomposition of organic residues leads to the formation of hydrogen sulfide.
The depth of the hydrogen sulfide layer in the Black Sea is not the same everywhere. Off the coast of Crimea, the upper boundary of this layer lies at a depth of 150 meters, off the coast of the Caucasus - 200 meters, and in the central part of the sea 80-100 meters. The surface of the hydrogen sulphide layer in the sea rises to the center in the form of a dome and descends near the coast. This position of the surface of the hydrogen sulfide layer is a consequence of the greater mixing of waters in the coastal part.
Often from vacationers in Sochi, you can hear the question: are the Matsesta waters connected with the hydrogen sulphide of the Black Sea? Unfortunately, this has not yet been clarified at this time. Among researchers, there are supporters of both a positive and a negative answer to this question. There are several hypotheses regarding the origin of Matsesta waters: some scientists suggest that waters from the deep layers of the Black Sea flow through cracks under the Caucasus Mountains, when in contact with rocks, the composition of the waters changes somewhat; others believe that Matsesta waters come into wells from the bowels of the earth and are not associated with the waters of the Black Sea; still others explain the origin of the Matsesta springs by the penetration of ordinary rainwater through cracks, which, when moving in rocks, were saturated with salts and gases; finally, the fourth believe that Matsesta waters are ancient sea waters buried in the bowels of the Earth.
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The sea covers most of the planet Earth. But what do we know about him? What is seawater made of? What are her physical properties? How is sea water different from drinking water? And how to make one from another? We will try to answer all these questions in turn.
Just salt water?
Many people know what the sea tastes like, and those who do not know, guess. It's salty. But is it really possible to create the sea at home by just mixing salt and water? This is not entirely true. The amount of ordinary sea water is 96.5%. The remaining 3.5% are impurities. Their exact composition was found out only at the end of the 19th century, during a round-the-world expedition. But long before that, scientists knew that the impurities that make water so salty are not ordinary table salt. In fact, all the elements from periodic system Mendeleev. Their presence is minimal, but undeniable.
In the same expedition, 77 water samples were taken in different regions of the World Ocean. Then an amazing discovery was made: despite the huge amount of sea water on the Earth's surface, the percentage of the main ions in it always remains unchanged. What this means, we will analyze below. At the same time, we will find out what seawater consists of.
Salt consistency
It was this discovery, also called Dietmar's law, that was made on a round-the-world expedition of the late 19th century. The chemist, whose name was given to this pattern, found that the quantitative ratio of the main ions in seawater is practically unchanged in different regions of the planet. The proportion of other substances is so small that it is not significant and is not taken into account when carrying out various hydrochemical studies.
The main ions, i.e., substances in an amount of more than 0.01%, make up the bulk of the salts. It is they who mainly affect the physical and chemical.Their number depends on various factors, including conditions environment... But with a total salt concentration in seawater equal to 35.16 ‰, the masses of impurities have a clear meaning given in the table below. Let's see what seawater consists of.
Name | Quantity, g / kg | Name | Quantity, g / kg |
Strontium | |||
Boric acid | |||
Hydrocarbonates | |||
Sulphates | |||
As we can see, the majority are chlorides. Taking into account the constancy of the salt composition, on the basis of these data, it is possible to determine the complete composition of the seawater sample. To do this, calculate the concentration of chlorine, and on the basis of the data obtained, they find out by the method of ratios what proportion the remaining elements make up.
Physical properties
Like any other substance, seawater has different characteristics that scientists learn from research. This data allows you to get an idea of the many processes occurring at depth and affecting our planet. For example, not everyone knows that water has the ability to compress. Under the pressure of the mass acting on it from above, it can change its volume.
On the surface, this is almost imperceptible, but the deeper, the clearer this feature becomes. Under pressure of hundreds of atmospheres, the compressibility reaches a fairly large scale. Scientists argue that if it were not for this property of water, the ocean level would be 30 meters higher. In this case, the surface of the Earth would look very different.
Salinity
We have already figured out how much salt is in sea water, and we know that its amount is almost constant. Nevertheless, it varies slightly - from 33 to 37 ‰, with rare exceptions. The average value is 34.72 ‰. This indicator depends on the amount of precipitation falling in a particular region, the air temperature, which affects the intensity of evaporation, and the number of fresh water bodies directly connected to the sea.
The highest percentage of salinity recorded in Atlantic Ocean... The average in its northern part is 35.06 ‰. Smallest value belongs The Pacific... Nevertheless, there are water bodies in which the salinity indicator significantly exceeds the average values. These include the Mediterranean and Red Seas. High air temperatures, high evaporation rates and low rainfall raise the salinity level to a record 38-42 ‰. In general, the composition of the seawater of the Black Sea and many others is approximately the same. This is probably because they are all related.
Some claim that sea water contains 5 ‰ salt. But this indicator is extremely rare, only in mineral lakes. For example, level is 11, Black is 18 ‰, Red is 41 ‰, and Dead is 300 ‰.
Temperature
It would be naive to believe that this indicator is the same for all sea water in the world. The air temperature in regions close to the poles drops to minimum levels. On the other hand, at the equator, there is always stable hot weather. But the range of changes in water temperature is much lower, it ranges from -2 to 30 o C. The average in the entire World Ocean is only 3.73 o C. Moreover, the water on the surface is several times warmer than at a depth of 2-5 thousand. m.
It may cause some bewilderment that the temperature of sea water in some regions drops to -2 o C. Everyone knows that at 0 o C H 2 O turns into ice. It is, but seawater, as we have already found out, includes impurities that change its characteristics, including lowering the freezing point. The higher the percentage of salinity, the lower this figure. For example, with a relatively small amount of salt in water (24.7 ‰), the freezing point will be -1.33 o C.
Density
The slightest changes in this indicator cause the movement of water and lead to the emergence of vertical and horizontal flows. That is why the density of sea water is studied in any oceanological research. It is measured in kg / m 3 and is the mass of a unit volume.
The density of fresh water at a temperature of 4 ° C is 1000 kg / m 3, and sea water at a salinity of 35 ‰ - 1027.81 kg / m 3. This difference arises from the impurities that make up its composition. The more salt there is in seawater, the higher the density will be. Usually its value ranges from 1025 to 1033 kg / m 3.
In addition, the density of seawater varies with depth: the closer to the surface, the lower it is. But there are exceptions. For example, with intense evaporation associated with high temperature air, salinity increases on the surface. Accordingly, the density of the sea in the upper layers is growing.
Chemical composition
As we found out above, the amount of impurities in seawater is about the same. But what exactly are the substances that make it what it is?
It is believed that modern chemical composition sea water formed about 1 billion years ago. Even then, it was as salty as it is now. And especially surprising seems to be the assumption of R. Quinton, who in 1904 stated that the mineral composition of sea water and blood is approximately the same. In 1910, A. B. Mallun confirmed this conjecture. In his opinion, the set chemical substances in the seawater of the period when the first bony and cartilaginous fish appeared, it is similar to the blood of all animals. But until now, this hypothesis has both supporters and opponents.
Sea water contains various substances, the percentage of which is shown in the table below.
Chemical elements | Percentage |
Oxygen | |
Strontium | |
This listing may vary slightly from region to region. For example, the composition of the Black Sea seawater is saturated with hydrogen sulfide, since sulfate-reducing bacteria are especially active here.
Where does salt come from?
We have already found out what the percentage of seawater is. But where do all these substances come from and why does the ocean taste like this?
In fact, salts are found not only in seawater, but also in freshwater bodies. Only the concentration of minerals there is so low that it cannot be recognized without special analysis. Rivers wash salts from the soil on their way, which later enter the ocean. Under the influence of temperature, the water in the sea evaporates, and the minerals remain in place.
But even if this process lasted for many years, the sea water would not become so salty. The beginning of everything was laid by volcanic activity taking place in the earth's crust. Magma, when it comes to the surface, mixes with water and saturates it with a variety of water. That is why the chemical composition of the ocean was formed about 1 billion years ago, when volcanic activity was most active.
Can I drink it?
Surely in books or films you have come across statements that sea water should not be drunk under any circumstances? But why? After all, this is the same water as any other, only with a small amount of impurities. In fact, it is because of them that it is undrinkable.
The amount of salt in seawater is so great that to remove them from the body, you will need several times more H 2 O than was drunk initially. That is why, after any salty food, you are so thirsty. And in sea water, as we have already found out, average salinity is almost 35 ‰. This is a lot.
In the 1950s, the doctor and part-time traveler Alain Bambar proved from his own experience that seawater can be drunk without harm for health within a week. But it is not worth checking this statement on yourself.
But is it really all the water in the oceans is wasted and absolutely cannot be used for drinking? Maybe, but only after going through the desalination process.
How do you get rid of salt?
We figured out what seawater is made of. But in order for it to become drinkable, the amount of impurities in it must be reduced by almost 70 times. But how can this result be achieved?
There are several methods of ion exchange, distillation, electrodialysis, etc. The most effective are those that require the least energy and financial costs. The most common method is distillation, but no less popular and reverse osmosis... In this case, high pressure is used for water purification. The result is 16,000 liters for just $ 1.
The electrodialysis method, as the name implies, is carried out using electrodes. At the moment the current is turned on, the cations and anions, which we talked about at the very beginning of the article, tend to the cathode and anode, respectively, through special membranes. The water between the electrodes is gradually desalinated.
The benefits of sea water
Often, those who suffer from respiratory diseases are sent to rest on the coast. This is correct, since sea water has a beneficial effect on the lungs, bronchi and ligaments. The liquid saturated with minerals disinfects and destroys pathogenic microbes. What else is it useful for?
Staying in and bathing in salt water has a general strengthening effect on the human body, and also improves work endocrine system... The result is increased immunity.
Bromine, calcium and iodine contained in seawater help to strengthen tooth enamel and gums when rinsing. To achieve the best effect, rinse your mouth several times a week for 2-3 minutes. Of course, only specially purified sea water, which can be found in a pharmacy, is suitable for these purposes. Warm up to room temperature before use.
Sea water is a good antiseptic. It promotes healing of small wounds and abrasions, reduces itching from insect bites.
