Everything that surrounds us has its own physical and chemical nature. What is called a substance and what types of it exist? It is a physical substance with a specific chemical composition. In Latin, the word "substance" is denoted by the term Substantia, which is also often used by scientists. What is it like?
To date, more than 20 million different substances are known. There are all kinds of gases in the air, in the ocean, seas and rivers - water with minerals and salts. The solid surface layer of our planet consists of numerous rocks. A huge number of different substances are present in any living organism.
General concepts
In modern chemistry, a substance, the definition of which is understood as a type of matter, has a rest mass. It consists of elementary particles or quasiparticles. An integral sign of any substance is its mass. As a rule, at relatively low densities and temperatures, such elementary particles as electrons, neutrons and protons are most often found in its composition. The last two are atomic nuclei. All these elementary particles form substances such as molecules and crystals. At its core, their atomic substance (atoms) consists of electrons, protons and neutrons.
From the point of view of biology, “substance” is the concept of matter, which forms the tissues of any organisms. It is part of the organelles that are present in cells. In a general sense, “substance” is a form of matter from which all physical bodies are formed.
Substance properties
The properties of a substance are called a set of objective characteristics that determine individuality. They make it possible to distinguish one substance from another. The most characteristic physical and chemical properties of a substance:
• density;
• boiling and melting points;
• thermodynamic characteristics;
• Chemical properties;
• crystal structure values.
All parameters listed are constant constants. Since all substances differ from each other, they have certain physical properties. What is meant by this concept? The properties of a substance are called its features, determined by measurement or observation, without transforming it into another substance. The most important of them are:
• state of aggregation;
• color and gloss;
• odor;
• taste;
• insolubility or solubility in water;
• melting and boiling points;
• density;
• electrical conductivity;
• thermal conductivity;
• hardness;
• fragility;
• ductility.
For crystalline substances , a physical property such as form is also characteristic. Color, taste, smell are determined visually and with the help of the senses. Physical parameters such as density, melting point and boiling point, electrical conductivity are calculated using various measurements. Information on the physical properties of most substances is presented in special directories. They depend on the state of aggregation of the substance. So, the density of water, ice and steam is completely different. Oxygen in the gaseous state is colorless, and in the liquid state it has a blue tint. Due to differences in physical properties, many substances can be distinguished. So, copper is the only metal with a reddish tint. Only rock salt has a salty taste. In most cases, in order to determine a substance, several well-known properties must be taken into account.
Relation of concepts
Many people confuse the concepts of “chemical element”, “atom”, “simple substance”. In fact, they differ from each other. So, an atom is a concrete concept, since it really exists. A chemical element is an abstract (collective) definition. In nature, it exists only in the form of bound or free atoms. In other words, it is a simple or complex substance. Each chemical element has its own symbol - sign (symbol). In some cases, it also expresses the composition of a simple substance (B, C, Zn). But often this symbol denotes only a chemical element. This is clearly demonstrated by the oxygen formula. So O is just a chemical element, and the simple substance oxygen is denoted by the formula O 2 .
There are other differences between these concepts. It is necessary to distinguish the characteristics (properties) of simple substances, which are a combination of particles, and a chemical element, which is an atom of a certain type. There are certain differences in the names. Most often, the designation of a chemical element and a simple substance coincides. However, there are exceptions to this rule.
Classification of substances
What is called matter from the point of view of science? The number of different substances is very large. A natural substance, the definition of which is associated with its natural origin, can be organic or inorganic. Man learned to synthesize many compounds artificially. The definition of "substance" means the division into simple (individual) substances and mixtures. Attitude to classification depends on how many of them are included in it.
The definition of a simple substance understands an abstract concept, which means a set of atoms interconnected according to certain physicochemical laws. Despite this, the boundary between it and the mixture is very vague, since some substances have an unstable composition. The exact formula has not yet been proposed for them. Due to the fact that only its final purity is achievable for a simple substance, this concept remains an abstraction. In other words, in any of them there is a mixture of chemical elements in which one prevails. Often, the purity of a substance directly affects its properties. In a general sense, a simple substance is built from atoms of one chemical element. For example, an oxygen gas molecule contains 2 identical atoms (O 2 ).
What is called a complex substance? Such a chemical compound includes various atoms that make up the molecule. It is sometimes called a mixed chemical substance. Complex substances are called mixtures whose molecules are formed from atoms of two or more elements. So, for example, in a water molecule there is one oxygen atom and 2 hydrogen (H 2 O). The concept of a complex substance corresponds to a molecule containing various chemical elements. There are many more such substances than simple ones. They can be natural and artificial.
Simple and complex substances, the concept of which is somewhat arbitrary, differ in their properties. So, for example, titanium becomes strong only when it is delivered from oxygen atoms to less than one hundredth of a percent. A complex and simple substance, the chemical definition of which is a little difficult to perceive, can be of two types: inorganic and organic.
Inorganic substances
Inorganic are all chemical compounds that do not contain carbon. This group also includes some substances that contain this element (cyanides, carbonates, carbides, carbon oxides, and several other substances). They do not have a skeleton characteristic of organic substances. Everyone can name a substance according to the formula thanks to the periodic system of Mendeleev and the school chemistry course. All of them are indicated in Latin letters. What is called a substance in this case? All inorganic substances are divided into the following groups:
• simple substances: metals (Mg, Na, Ca); non-metals (P, S); noble gases (He, Ar, Xe); amphoteric substances (Al, Zn, Fe);
• complex: salts, oxides, acids, hydroxides.
Organic matter
The definition of organic matter is quite simple. These substances include chemical compounds that contain carbon. This class of substances is the most extensive. True, there are exceptions to this rule. So, organic substances do not include: carbon oxides, carbides, carbonates, carbonic acid, cyanides and thiocyanates.
The answer to the question “name organic substances” includes a number of complex compounds. These include: amines, amides, ketones, anhydrides, aldehydes, nitriles, carboxylic acids, organosulfur compounds, hydrocarbons, alcohols, ethers and esters, amino acids.
The main classes of biological organic substances include lipids, proteins, nucleic acids, carbohydrates. In addition to carbon, they include hydrogen, oxygen, phosphorus, sulfur, nitrogen. What are the characteristics of organic substances? Their diversity and structural diversity is explained by the peculiarities of carbon atoms, which are able to form strong bonds when connected in chains. Thanks to this, very stable molecules are obtained. Carbon atoms form a zigzag chain, which is a characteristic feature of organic substances. In this case, the structure of the molecules directly affects the chemical properties. Carbon in organic substances can be combined into open and cyclic (closed) chains.
State of aggregation
The definition of "substance" in chemistry does not give a detailed concept of its state of aggregation. They differ in the role that the interaction of molecules plays in their existence. There are 3 states of aggregation of a substance:
• Solid, in which the molecules are tightly connected. A strong attraction is established between them. In the solid state, the molecules of the substance are not able to move freely. They can only make oscillatory movements. Due to this, solids perfectly retain their shape and volume.
• Liquid, in which molecules are freer and can move from one place to another. Due to these properties, any liquids can take the form of a vessel and flow.
• Gaseous, in which elementary particles of matter move freely and randomly. The molecular bonds in this state are so weak that they can be far away from each other. In a gaseous state, a substance is capable of filling large volumes.
Using water as an example, it is very easy to understand the difference between ice, liquid, and steam. All these states of aggregation do not belong to the individual characteristics of a chemical substance. They correspond only to the states of existence of the substance, depending on external physical conditions. That is why water cannot be unambiguously attributed to a sign of liquid. When external conditions change, many chemicals pass from one state of aggregation to another. During this process, intermediate (borderline) types are detected. The most famous of them is an amorphous state called glassy. Such a definition of "substance" in chemistry is associated with its structure (in Greek amorphos - formless).
In physics, another aggregate state called plasma is considered. It is fully or partially ionized and is characterized by the same density of negative and positive charges. In other words: plasma is electrically neutral. This state of matter arises only at extremely high temperatures. Sometimes they reach thousands of Kelvin. By some of its properties, plasma is the opposite of gas. The latter has low electrical conductivity. Gas consists of particles that are similar to each other. However, they rarely collide. Plasma has a high electrical conductivity. It consists of elementary particles that differ in electric charge. They constantly interact with each other.
There are also such intermediate states of a substance as a liquid crystal and a polymer (highly elastic). In connection with the presence of these transitional forms, specialists often use the broader concept of “phase”. Under certain conditions, quite different from ordinary, some substances pass into special states, for example, superconducting and superfluid.
Crystals
Crystals are solid substances that have the natural form of regular polyhedra. It is based on their internal structure and depends on the location of its constituent atoms, molecules and ions. In chemistry, it is called a crystal lattice. Such a structure is individual for each substance; therefore, it is one of the main physicochemical parameters.
The distances between the particles that make up the crystals are called the lattice parameters. They are determined using physical methods of structural analysis. Often solids have more than one form of crystal lattice. Such structures are called polymorphic modifications. Among simple substances, the rhombic and monoclinic forms are common. Such substances include graphite, diamond, sulfur, representing hexagonal and cubic modifications of carbon. This form is also noted in complex substances, such as quartz, cristobalite, tridymite, which are modifications of silicon dioxide.
Matter as a form of matter
Despite the fact that the concepts of “substance” and “matter” are very close in meaning, they are not completely equivalent. This is claimed by many scientists. So, when mentioning the term “matter” most often they mean crude, inert and dead reality, subject to the rule of mechanical laws. Under the definition of "substance" is more understood material, which, due to its shape, causes the idea of ​​vitality and design.
Today, scientists consider matter to be an objective reality that exists in space and changes over time. It can be presented in two forms:
• The first has a wave nature. It includes weightlessness, permeability, continuity. It can spread at the speed of light.
• The second is corpuscular, with a mass of rest. It consists of elementary particles that differ in their localization. It is impenetrable or impermeable and cannot propagate at the speed of light.
The first form of existence of matter is called the field, and the second - substance. They have a lot in common, because even electrons have the properties of a particle and a wave. They appear at the level of the microworld. That is why the separation of the field and the substance is very convenient.
The unity of matter and field
Scientists have long established that the larger and larger the elementary particle of a substance, the sharper its individuality and delimitation is expressed. In this case, the contrast between the substance and the field, which is characterized by continuity, is brighter. The smaller the elementary particles of a substance, the less its mass. In this case, contrasting it with the field becomes more complicated. In various microwaves, it generally loses its meaning, since different elementary particles are quanta excited by states of various fields (electromagnetic - photons, nuclear - mesons).
The unity of matter and field and the absence of a clear boundary between them is expressed in the fact that under certain conditions particles arise due to the field, and in other cases - vice versa. A good example of this is the phenomenon of annihilation (the phenomenon of the transformation of elementary particles). Any material body is a stable whole, possible due to the connection of its elements through the fields.