Chemical ChangePhysical Change, What is Physical Change, What is Chemical Change?

1: Efflorescence refers to the phenomenon that crystalline hydrates lose their crystalline water at room temperature and in dry air.

2: The so-called deliquescent refers to the deterioration of solid powder after the reaction with some components in the air (especially water and carbon dioxide). Of course, it is a chemical change, for example, in daily life, the alkali block (Na2CO3·10H2O) becomes an alkaline surface (Na2CO3), which is a weathering phenomenon.

The phenomenon of heating crystalline hydrates to cause them to lose their crystalline water is not called weathering, but dehydration.

Due to the characteristics of crystal structure and the influence of external conditions, some crystals only lose part of the crystal water; Some crystals can lose all the crystal water; Some crystals first lose part of the crystal water, and then gradually lose all of the crystal water. It can be seen that weathering does not necessarily mean the loss of all crystal water. Therefore, there are sodium carbonate decahydrate (Na2CO3·10H2O), sodium carbonate heptahydrate (Na2CO3·7H2O) and sodium carbonate monohydrate (Na2CO3·H2O).

The weathering of crystalline hydrate is different from the weathering of natural rocks, the former is the loss of crystalline water, while the latter refers to the phenomenon that rocks interact with air, water, carbon dioxide and other substances for a long time, and a complex chemical reaction occurs, resulting in rock disintegration and fragmentation.

Therefore, sun-drying and drying are physical changes, and weathering and deliquescent are chemical changes.

Weathering is a chemical change.

The rest is physics.

All are physical changes.

A chemical change is a change in the substance before and after a reaction, and a change in the state is a physical change.

Physical changes, sun drying, drying.

Chemical changes, weathering, deliquescent.

Physical changes, dripstone wears and no new matter is generated.

Physical change refers to the fact that although the state of matter has changed, generally speaking, the composition of the substance itself has not changed. For example, changes in position, volume, shape, temperature, pressure, and conversion between gaseous, liquid, and solid states.

There are also the interaction between matter and electromagnetic fields, the interaction between light and matter, and the interaction and transformation between microscopic particles (electrons, atomic nuclei, elementary particles, etc.), all of which are physical changes.

Chemical change refers to the process of the conversion or transfer of atoms or electrons between molecules in contact with each other to form new rock bent molecules accompanied by energy changes, which is essentially the breaking of old bonds and the formation of new bonds.

The difference between a physical change and a chemical change is whether or not a new substance is formed.

Connection: There must be physical changes in the process of chemical change, and the process of physical change may be accompanied by chemical change.

Physical Change: No change in the formation of other matter. For example: a light bulb glows, ice melts into water; Water evaporates into water vapor; Iodine, sublimation of dry ice, volatilization of gasoline, melting of candles, etc., are all physical changes.

Chemical change: A change in the formation of other substances when a substance changes.

For example: wood burns, iron rusts, food rots.

Chemical changes are often accompanied by some reaction phenomena while generating new substances, such as color changes, gas release, precipitation, etc., chemical changes not only generate other substances, but also accompanied by energy changes, which are often manifested as endothermy, exothermic, luminescence, etc.

Chemical change is prevalent in production and life. The change that produces a new substance is a chemical change. Such as the rust of iron, the fireworks of festivals, the neutralization of acid and alkali, the burning of magnesium strips, and so on.

On a macroscopic scale, it can be seen that various chemical changes produce new substances, which is characteristic of chemical changes. Summary: A change in a new substance is a chemical change.

1. Connection: chemical changes must contain physical changes, and there must be no chemical changes in physical changes.

2. Differences. 1) The essential difference between the two is the generation of new substances.

2) Physical change is only a change in form, property, etc., while chemical change is the formation of new substances.

Examples of physical changes: water evaporates and solidifies, sugar cubes melt, carbon dioxide condenses into dry ice, wine smells, wet clothes dry out.

Examples of chemical changes: sodium hydroxide deterioration, plant photosynthesis, hydrochloric acid rust removal, thermal decomposition of basic copper carbonate, rusting of iron in humid air, burning of candles.

1. The scale in the kettle is caused by calcium carbonate deposition;

2. The rust in the iron pot is ferric oxide and ferric oxide deposits;

3. The dirt in the toilet bowl is calcium carbonate;

4. The combustion of materials such as paper or wood produces water and carbon dioxide;

5. Iron rust produces rust.