How many forms does matter take? How do they change with each other? What are the conditions for change?

Strictly speaking, the physical solid state should be referred to as the "crystalline state", which is the state that various crystals have. The most common crystal is table salt (the chemical component is sodium chloride, the chemical symbol is NaCl). If you look at a grain of salt (preferably coarse salt), you can see that it consists of many cubic crystals. If you go to a geological museum you can also see many regular crystals of different colors and shapes, which are very beautiful. Matter in the solid state is characterized by a certain volume and geometry, in different directions in the physical properties can be different (known as "anisotropy"); have a certain melting point, that is, the temperature remains unchanged when melting.

In solids, molecules or atoms are arranged in regular periodic patterns, just as they are arranged equidistant from each other when we do exercises as a group. Each person moves in a certain position, just as each molecule or atom vibrates in its own fixed position. We call this structure of a crystal a "spatial dot matrix" structure.

2. Liquid

Liquids are fluid and take on the shape of whatever container they are placed in. In addition, unlike solids, liquids have "isotropic" characteristics (the same physical properties in different directions), this is because the object from the solid state into a liquid state, due to the increase in temperature makes the molecules or atoms move violently, and can not keep the original fixed position, so there is a flow. But then the attraction between the molecules or atoms is still relatively large, so that they will not disperse away, so the liquid still has a certain volume. In fact, in many small areas within the liquid there are still structures similar to crystals - "crystal-like regions". Mobility is created by the fact that the "crystal-like zones" can move around each other. Let's make an analogy, in the asphalt road to send the "traffic", each car inside the person is a fixed position of a "crystal-like zone", and the car can be relative movement between cars, which causes the fleet of vehicles as a whole flow.

3. Gaseous state

Liquid heating will become gaseous. At this point, the molecules or atoms move more vigorously and the "crystal-like zone" no longer exists. Because the distance between the molecules or atoms increases, the gravitational force between them can be ignored, so the gaseous state is mainly manifested in the molecules or atoms of their own irregular movement, which leads to the properties of gases as we know them: fluidity, no fixed shape and volume, can automatically fill any container; easy to compression; the physical properties of "isotropic". .

Clearly, the liquid state is the form that lies between the solid and gaseous states.

4. Amorphous - a special kind of solid

Is ordinary glass a solid? You must say, of course it is solid. In fact, it is not in the solid state (crystalline state). You must be wondering about this.

This is because glass has different properties and internal structure than crystals.

You can do an experiment by heating glass in a fire, and as the temperature rises, it softens and then gradually melts. In other words, glass does not have a fixed melting point. In addition, its physical properties are "isotropic". These are different from crystals.

After research, the internal structure of glass is not characterized by "spatial punctuation", but is similar to the structure of the liquid state. It is only the "crystal-like regions" that cannot move away from each other, resulting in a glass that is not fluid. We call this state "amorphous".

Strictly speaking, an "amorphous solid" is not a solid, since a solid is exclusively a crystal; it can be thought of as an extremely viscous liquid. Therefore, "amorphous" can be presented as another state of matter.

In addition to ordinary glass, "amorphous" solids are many, common rubber, paraffin, natural resins, asphalt and polymer plastics.

5. liquid crystal state - a form between the crystalline state and liquid

"Liquid crystal" is now no stranger to us, it is in the electronic watch, calculators, cell phones, pagers, micro-computers and televisions, etc., text and graphics display It has been widely used in electronic watches, calculators, cell phones, pagers, microcomputers and televisions.

"Liquid crystal" this material belongs to the organic compounds, so far the synthetic liquid crystal has reached more than 5000 kinds.

This material can be in a certain temperature range in the "liquid crystal state", that is, both with the liquid fluidity, but also with the crystal in the optical properties of the "anisotropy". It is sensitive to small changes in external factors (such as heat, electricity, light, pressure, etc.). It is these properties that we utilize to make it useful in many applications.

These "states of matter" can be observed under everyday conditions. However, with the advancement of experimental techniques in physics, some new "states of matter" have been discovered under the conditions of ultra-high temperature, ultra-low temperature, and ultra-high pressure.

6. Ultra-high-temperature plasma

This is a gas in about millions of degrees of extremely high temperature or in other particles under the strong collision of the state of matter, this time, the electron from the atom out of the free electrons. Plasma is a highly ionized gas, but it is in a different "state of matter" from the "gas state"--"plasma state "

The Sun is a highly ionized gas.

The Sun and many other stars are extremely hot planets, and they are plasma. Most of the matter within the universe is plasma. There is plasma on Earth too: the ionosphere at high altitudes, lightning, auroras, and so on. The ionized gases in fluorescent lights and mercury lamps are man-made plasma.

7. Supersolids at Ultra-High Pressure

At 1.4 million atmospheres, the atoms of matter can be "crushed". Electrons are all "out" of the atom, the formation of electron gas, the bare atomic nuclei closely arranged, the material density is very large, this is the supersolid state. A piece of supersolid matter the size of a ping-pong ball has a mass of at least 1,000 tons.

It has been well documented that white dwarfs at later stages of development of less massive stars are in this supersolid state. Its average density is tens to hundreds of thousands of times that of water.

8. Neutron states at ultrahigh pressures

At higher temperatures and pressures, atomic nuclei can also be "crushed". We know that the atomic nucleus consists of neutrons and protons, and at higher temperatures and pressures the protons absorb electrons and convert them into neutrons, and the material appears to be in a state where the neutrons are tightly packed in a state called the "neutron state".

It has been confirmed that the "neutron star" in the late stage of the development of intermediate-mass (1.44 to 2 times the mass of the Sun) stars is a kind of planet denser than white dwarfs, and its state of matter is the "neutron state".

Later stages of more massive stars, theory predicts that they will evolve into "black holes" that are denser than neutron stars, and there are no direct observations to confirm its existence. As for the "black hole" in the ultrahigh pressure under the action of matter and what physical state, there is no knowledge, pending future observations and research.

Matter in the high temperature, high pressure appeared in anomalous physical state, then in the low temperature, ultra-low temperature matter will not also appear some special form? The two states of matter described below are such cases.

9. Superconducting state

Superconducting state is some substances in the ultra-low temperature of the special state. The first to discover the phenomenon of superconductivity, is the Dutch physicist Kamerling Onass (1853 ~ 1926), in the summer of 1911, he experimented with mercury, and found that the temperature dropped to 4.173K when (about -269 ℃), mercury began to lose resistance. He then discovered that many materials have this property again: they lose resistance at a certain critical temperature (low temperature) (read "Advances in Low Temperature and Superconductivity Research"). Camerin Onass called the phenomenon of certain substances exhibiting zero resistance at low temperatures "superconductivity". The state of matter in which superconductors are found is the "superconducting state," and the superconducting state will be of great benefit to mankind in such areas as high-efficiency power transmission, magnetic levitation high-speed trains, and high-precision detection instruments.

The discovery of the superconducting state, especially its peculiar properties, has attracted worldwide attention, and people have invested a great deal of effort in the study of superconductivity, which is still a very popular scientific research topic. At present, the discovery of superconducting materials are mainly some metals, alloys and compounds, no less than a few thousand kinds, each of them corresponds to a different "critical temperature", the highest "critical temperature" has reached 130K (about minus 143 degrees Celsius), countries Scientists are desperately trying to room temperature (300K or 27 ℃) critical temperature sprint.

What is the structure of superconducting matter? Theoretical studies are still immature and need to be explored further.

10. Superfluid state

Superfluid state is a very peculiar physical state, which, as far as is known, occurs only in individual substances at ultra-low temperatures.

In 1937, the Soviet physicist Peter Leonidovich Kapitsa (1894-1984) was surprised to find that when the temperature of liquid helium was lowered to 2.17 K, it suddenly changed from the general fluidity of the original liquid to "superfluidity": it could pass through the very smallest of particles, which cannot even pass through gases, without any obstacles. It can pass unimpeded through tiny holes or slits (with a linearity of about 100,000th of a centimeter) through which even gases cannot pass, and it can also "crawl" along the walls of the cup and out of the mouth. We call the state of matter with superfluidity "superfluidity". However, only liquid helium below 2.17 K has been found in this state. The structure of matter in the superfluid state is also being explored theoretically.

The above is only a list of the 10 states that have been discovered so far, and there are many more, such as superionic states, radiation field states, and quantum field states, which are not listed here for lack of space. We believe that, with the development of science, we will recognize more states of matter, solve more mysteries, and use their peculiar properties for the benefit of mankind.