Sea water is salty

Often swim into the sea of people, will find it in the pool or rivers and lakes in the difference. First of all, your body will feel more than easy to float in the pool; Secondly, the occasional drink into a sea water, will feel bitter and salty. Why is this? The original sea water in a large number of dissolved salts. The salty sea water, the buoyancy of the big hold up the human body; dissolved salts in seawater, some salt, and some are bitter. Which sodium chloride is the salt we eat is salty. Another called magnesium chloride is the point of tofu with the brine, is bitter.

According to measurements, the total water content of the various salts is generally 3% -3.5%, the scientists calculated that, in a cubic kilometers of seawater contains more than 2,700 tons of sodium chloride, magnesium chloride 3.2 million tons, Carbonate 2.2 million tons of magnesium, magnesium sulfate 1.2 million tons, etc., the water contains 5X1016 tons of salt.

At present, sea water has been found more than 80 kinds of chemical elements. Oceanographer put these elements into three categories, containing 100 mg per liter of sea water above the element, called constant elements; containing 1-100 mg of elements, called trace elements; containing 1 mg of the following elements, called trace elements. The main elements of sea water contains sodium, calcium, potassium, rubidium, strontium, barium and other metal elements, chlorine, bromine, iodine, oxygen, sulfur and other non-metallic Lenovo Y500 battery elements. Them in the sea mainly in form of compounds to a wide variety of salts there.

Around the world, the salinity of seawater is as much of it? No, evaporation of sea water in a large concentration of salt; the other hand, more precipitation, or river water into the waters, sea water salt concentration on the small. Therefore, in some specific area, the salt concentration can be particularly high, such as Asia and Africa at the junction of the Red Sea, the strong solar radiation, water evaporation big around it is desert, high temperature, rainfall has been particularly low, So, where sea water salinity as high as 4%, or even as high as 4.3%, as the world’s largest sea salt.

Also some sea areas may be particularly low salinity, such as rainfall and river flows, in particular the northern Baltic Sea more than wave Niya Hai, salinity reduced to only 3% of even 0.1% -0.2%, the Caspian Sea water and salt become the world’s oceans the lowest of the sea. China sea water salinity, as the rivers into the sea, so it is only 3.2% of the average salinity, and some sea areas are even lower.

In the rivers into the sea of fresh water and sea water intersection where there is significant difference between salinity, water salinity difference can be the most abundant, is the development and utilization of chemical energy in sea water ideal place. In the atmosphere, the cold air and warm air have a tilt at the junction between the peak surface density of cold air at the bottom, density of warm air at the top. Between freshwater and salt water and the atmosphere is similar to have a tilted interface, brine density, Shen at the bottom of fresh water density, floating on top, like the tongue of the salt water to fresh water as inserted into the lower part, so the “salt tongue” known. Salt and fresh water interface, is the salinity difference to beautifully place, only here, deep with the sea water helps bring energy to studio 1435 battery chemical energy.

Why osmotic pressure and salinity difference can exist between salt and fresh water salinity difference can it? To answer this question, we need to start with from the osmotic pressure.

Penetration phenomenon is very widespread phenomenon, such as soy beans soaked in water expands, it is because the water surface by soybean (molecular physics, said that for the semi-permeable membrane surface) is made of infiltration

Into the.

Semipermeable membrane is what? It plays a role in the infiltration of what role? First of all, for example, animal bladder is semi-permeable membrane, which only allows water through but not allow alcohol through; another, such as animal and plant cell membrane is semi-permeable membrane; have a variety of artificial semi-permeable membrane, such as iron cyanide copper precipitation in unglazed ceramic membrane made of plastic film cotton.

Now like to explain the permeation phenomenon; in the semi-permeable membrane separates a concentration difference between the same kind of solution, resulting in low concentration solution through the high concentration solution into the phenomenon, this phenomenon is called osmosis.

So, what is the osmotic pressure it? When the infiltration phenomenon, we have a large concentration of the solution in a mechanical pressure is applied, just to prevent the concentration of dilute solution to the solution of large infiltration occurs, the mechanical pressure is equivalent to the osmotic pressure between these two strong solution, or infiltration pressure.

Then, sea water and fresh water infiltration between the phenomenon and the osmotic pressure is like? There are a lot of salt dissolved in seawater, salt dissolved in water will be ionized into positive and negative charge with two types of ions, such as sodium chloride, the ionization is a positively charged sodium ions and negatively charged chloride ions. If the sea water and fresh water across the floor to allow water molecules to pass through only and not for positive and negative VGP-BPS3 battery ions through the semipermeable membrane, then the infiltration phenomenon arises between them, fresh water to sea water penetration, and produce a osmotic pressure.

Now let’s do a simple experiment, you can verify the existence of penetration phenomena and osmotic pressure. Take a funnel, with a pig bladder as a semipermeable membrane as it covered, and then reversed, so that long neck up and poured into the sea, then it is put into fresh water tank. Then in the semi-permeable membrane near the interesting phenomenon, fresh water in the water molecules free access to water, sea water of chlorine and sodium ions can not enter the water. However, the water molecules in seawater can also be run in fresh water to go, but a much less progress, so after a while, long-necked funnel in the sea water rose, the ocean salinity decreased. This process has been carried out to increase the height of water generated by pressure, is equal to the osmotic pressure between seawater and fresh water up. Elevated sea water column can be used to measure the size of the osmotic pressure.

Determination was done, the temperature 201, the salinity is 3.57. Standard sea water, and the osmotic pressure between pure water up to 2.48 MPa, the equivalent of 256.2 meters or 250 meters of water column with high column of water high. Shows that osmotic pressure is a lot of pressure.

Osmotic pressure of the size and temperature, concentration. The higher the temperature, the greater the osmotic pressure; concentration greater the difference, the greater the osmotic pressure. In the ocean, the salinity difference between sea water and fresh water the most, the greater the osmotic pressure between them. This is why the river into the sea where seawater and freshwater convergence is the salinity difference can be rich in places.