A substance is a form of matter consisting of fermions or containing fermions along with bosons ; has a rest mass , unlike some types of fields , such as electromagnetic .
Usually (at relatively low temperatures and densities) a substance consists of particles , among which electrons , protons and neutrons are most often found. The last two form atomic nuclei , and all together - atoms (atomic matter), of which - molecules , crystals, and so on. In some conditions, such as in neutron stars , quite unusual types of matter may exist. The concept of matter is sometimes used in philosophy as the equivalent of the Latin term substantia [1] .
Content
Properties of a substance
All substances can expand, contract, turn into a gas, liquid or solid. They can be mixed to produce new substances.
Each substance has a set of specific properties - objective characteristics that determine the individuality of a particular substance and thereby distinguish it from all other substances. The most characteristic physical and chemical properties include constants - density , melting point , boiling point , thermodynamic characteristics , crystal structure parameters, chemical properties .
Aggregate states
Almost all chemicals in principle can exist in three states of aggregation - solid, liquid and gaseous. So, ice, liquid water and water vapor are solid, liquid and gaseous states of the same chemical substance - H 2 O water. Solid, liquid and gaseous forms are not individual characteristics of chemicals, but correspond only to different, depending on external physical conditions of the existence of chemicals. Therefore, it is impossible to attribute to water only a sign of liquid, oxygen - a sign of gas, and sodium chloride - a sign of a solid state. Each of these (and all other substances) when changing conditions can go into any other of the three states of aggregation.
In the transition from ideal models of solid, liquid, and gaseous states to real states of matter, several boundary intermediate types are discovered, of which the well-known are the amorphous (glassy) state, the state of a liquid crystal, and the highly elastic (polymer) state. In this regard, they often use the broader concept of “ phase ”.
In physics, the fourth aggregate state of a substance is considered - plasma , a partially or fully ionized substance in which the density of positive and negative charges is the same (plasma is electrically neutral).
Under certain conditions (usually quite different from the usual ones), certain substances can pass into such special states as superfluid and superconducting .
Substance in Chemistry
In chemistry, a substance is a type of matter with certain chemical properties - the ability to participate in chemical reactions in a certain way.
All chemicals are made up of particles - atoms , ions or molecules ; in this case, the molecule can be defined as the smallest particle of a chemical substance with all its chemical properties. In fact, chemical compounds can be represented not only by molecules, but also by other particles that can change their composition. The chemical properties of substances, unlike the physical ones, are independent of the state of aggregation , thus ice and water are one and the same substance from the point of view of chemistry. A chemical substance is characterized by its composition and structure, substances with the same chemical composition may be different due to different structures - for example, white phosphorus and black phosphorus . [2] [3]
See also
- Simple substances
- Compound substance
Notes
- ↑ See, for example, the philosophical dictionary of G. N. Teplov , published in 1751.
- ↑ L. Alikberova. Substances in chemistry . www.alhimik.ru. Date of treatment October 22, 2017.
- ↑ Super User. The concept of the structure of matter . ucheba-service.ru. Date accessed October 22, 2017. (unavailable link)