What is the essence of a substance dissolved in water?

1 First of all, this is the encyclopedia's explanation, that is, the original words of inorganic textbooks.

One is the diffusion process of solute molecules (or ions), which is a physical process that requires the absorption of heat; The other is the process of forming solvent (hydration) molecules (or hydrated ions) by the interaction of solute molecules (or ions) and solvent (water) molecules, which is a chemical process that emits heat. When the heat released is greater than the heat absorbed, the temperature of the solution will increase, such as concentrated sulfuric acid, sodium hydroxide, etc.; When the heat released is less than the heat absorbed, the temperature of the solution will decrease, such as ammonium nitrate, etc.; When the heat emitted is equal to the heat absorbed, the temperature of the solution does not change, such as salt, sucrose.

After some solutes are dissolved, they will change the properties of the original solvent, such as sodium chloride dissolved in water and ionized as free-moving sodium ions and chloride ions, so the solution formed is conductive (pure water does not conduct electricity); Ethylene glycol dissolves in water, which lowers the freezing point of water.

2 I understand.

In fact, it is understood this way:

At present, chemistry has not yet understood some of the microscopic forms of water, let alone the detailed mechanism of dissolution.

So it can only be explained in terms of thermodynamics. Of course, I don't know if you are interested in the explanation of thermodynamics. In the dissolution process, the solid changes from a regular crystal to a chaotic movement of solvated particles, and the entropy is to be increased, while the thermodynamic temperature is always positive (i.e., the third law of thermodynamics), so it is easy to see that for a specific dissolution process, the entropy change is positive.

Summary: Dissolution can increase the degree of chaos! So dissolve.

Of course, physicists and chemists have a lot of problems that they don't have to explain in this regard, so I'll have to tell you about it in an easy-to-understand way.

The essence of dissolution replaces the intermolecular and intermolecular forces of solute and solvent with the intermolecular forces of solute and solvent.

The dissolved solute molecules are dispersed and have no property of clumping together, and the changes that occur when light passes through them are different, and the reflection is visually invisible.

The process of dissolving a substance is the process by which solute particles are dissolved in a solvent. There are two processes in which substances are dissolved: the physical process, i.e., the molecular process, and the chemical process, i.e., the hydration process. That's all I know, I don't know if I can help you with that

Because there are gaps between the molecules.

Because of the principle of similarity and dissolution.

The principle of like dissolves like refers to the fact that due to the electrical interaction between polar molecules, the solute composed of polar molecules is easily soluble in the solvent composed of polar molecules, and insoluble in the solvent composed of non-polar molecules. The solute composed of non-polar molecules is easily soluble in solvents composed of non-polar molecules, and the solvents composed of polar molecules are insoluble.

For example, water and ethanol can be dissolved indefinitely, while ethanol and kerosene can only be miscible to a limited extent. Because the water molecule and the ethanol molecule have a -OH group, which is connected to a small atom or cluster of atoms, while kerosene is a mixture of 8 16 carbon atoms in the molecule, and its hydrocarbon part is similar to the ethyl group of ethanol, but it has no resemblance to water.

Nitrate is soluble (such as kno3, nano3, etc.), and sulfate is insoluble only barium sulfate (baso4).

Hydrochloride is insoluble only silver chloride (AGCL).

Carbonate, mostly precipitated, dissolved only potassium (K2CO3), sodium (Na2CO3), ammonia (NH4CO3).

There is only one alkali that is soluble in water: ammonia (NH4'H2O, ammonia), potassium (KHO), sodium (Naho), barium (Ba(Ho)2), calcium (Ca(Ho)2).

Do not add water to carbon dioxide.

Generate carbonic acid for the whole family.

Potassium, sodium, ammonium, nitrate are soluble, hydrochloride is insoluble silver mercurous;

Sulfate is insoluble barium and lead, carbon phosphate is mostly insoluble.

Most acids are soluble and alkaline, and only potassium, sodium, ammonium, and barium are soluble. ,8,Salt and sugar,0,

To see if there is precipitation, there are generally these methods:

1. Almost all solid oxides are precipitated (those that can react with water are not counted!) ）

2. Except for silicic acid and boric acid, acids do not precipitate in the range of junior and senior high schools.

3. Alkalis, except for sodium hydroxide, barium hydroxide, potassium hydroxide, calcium hydroxide and other alkali metals are soluble, as well as ammonia, everything else is precipitated.

4. Salts, that's complicated

In the middle and high school range, nitrate acetate is soluble.

Sulfate is only insoluble with lead sulfate and barium sulfate (there are a few slightly soluble, generally do not use the precipitation symbol).

Chloride is insoluble only silver chloride and mercurous chloride.

Carbonate and other salts are only soluble in Na, K, Ca, NH4, and nothing else except for a few such as magnesium carbonate that are slightly soluble.

There is a difference between the dissolution of a substance in water and the reaction between a substance and water, for example, sodium chloride is dissolved in water, but it is simply dissolved, and then sodium peroxide is dissolved in water and a chemical reaction occurs to form a sodium hydroxide solution. So there's a difference.

Sodium hydroxide, sulfuric acid, etc. are dissolved in water to exothermic, and many ammonium salts are soluble in water to absorb heat, such as ammonium chloride ammonium nitrate or something. ,9,BJBSD report.

Dissolution can be said to mean that a solid dissolves in a liquid to form a solution, but does not produce a new substance, but only a mixture of the two. Is it correct to understand that reacting with water is to produce a new substance, and it is a chemical reaction? The difference is that by reacting with water, a new substance is formed.

What kind of reaction should dissolution be, or what is it not?

Report a sunken fish in the open sea.

Dissolution is not any reaction, endothermic and exothermic is related to the breaking of ionic bonds or covalent bonds. Dissolution does not mean that there is absolutely no new substance produced, for example, ammonia water dissolves in water, which can ionize and produce a small amount of OH-. There is no need to distinguish this very carefully.

BJBSD Report.

That NAOH dissolves in water, does NAOH deteriorate, does it generate anything?

Report a sunken fish in the open sea.

This one definitely doesn't, if there is no CO2 in the water.

BJBSD Report.

That is, the deterioration of sodium hydroxide is only after reacting with carbon dioxide, and the reaction with water does not deteriorate, and no new substances are generated, so it can only be regarded as dissolved in water.

Report a sunken fish in the open sea.

If pure carbon dioxide is dissolved in pure water, no reaction will occur.

BJBSD Report.

The only thing related to the deterioration of sodium hydroxide is carbon dioxide, not water.

Report a sunken fish in the open sea.

I don't know what sodium hydroxide deterioration you are referring to, solid sodium hydroxide will deteriorate when absorbing carbon dioxide, sodium hydroxide will also absorb moisture, it is easier to react with CO2 after moisture absorption, and it deteriorates faster.

BJBSD Report.

That is to say, solid sodium hydroxide absorbs water, and deliquescent can accelerate the reaction between sodium hydroxide and carbon dioxide It should be, if it is very dry, it is not easy to deteriorate, can the dissolution of a substance in water be said to be a reaction between a substance and water, what is the difference between a substance dissolved in water and a reaction between a substance and water, and are the two the same? What substances dissolve in water to exothermic and what substances dissolve in water to endotherm.

Physical. The physical properties of the substance, such as color, smell, state, whether it is easy to melt, solidify, sublimate, volatilize high signal circle, and some properties such as melting point, boiling point, hardness, electrical conductivity, thermal conductivity, ductility, etc., can be measured by instruments.

There are also some properties that can be calculated through laboratory data, such as solubility, density, etc. Neither the matter changed before or after the experiment. These properties are all physical.

such as the evaporation of water; The candle is soft, not easy to collapse and dissolve in water, and the paraffin wax is generally white; paper shredding, etc.

Super, peroxide (metal); Active metals (magnesium and iron can react with water under heating conditions), potassium, calcium and sodium do not need to be heated to react directly, potassium oxide, calcium oxide, sodium oxide, ammonia (to produce ammonium hydroxide), sulfur dioxide, sulfur trioxide, phosphorus pentoxide, carbon dioxide, nitrogen dioxide ......Metal nitrides.