Today, there are about 2.5 million diverse compounds of both natural origin and synthesized artificially by humans. They are all very different, some of them are irreplaceable participants in biological processes that occur in living organisms. Compounds are distinguished from each other by the properties of substances. Characteristics and what else allows us to identify a particular chemical molecule, we will consider further.
What is a substance?
If a definition is given to this concept, then it is necessary to indicate its connection with physical bodies. After all, the substance is considered to be exactly what these bodies consist of. So, glass, iron, sulfur, wood are substances. Examples can be given endlessly. It is simpler to understand the following: the term in question denotes the entire variety of various combinations of molecules existing in the world, as well as simple monatomic particles.
Thus, water, alcohol, acids, alkalis, proteins, carbohydrates, salt, sugar, sand, clay, diamond, gases and so on - these are all substances. Examples allow us to more clearly grasp the essence of this concept.
The physical body is a product that is created by nature or man on the basis of various compounds. For example, a glass is a body that is made up of glass, and a piece of paper is a body that is processed pulp or wood.
Of course, all the molecules are different. What underlies their differences is called their properties - physical, organoleptic and chemical. They are determined using special methods, which each science has its own. It can be mathematical, analytical, experimental, instrumental methods, and even a lot of the most diverse. For example, science chemistry uses its own reagent for each substance, or rather, for its identification. It is selected based on the structural features of the molecule and the prediction of chemical properties. Then it is verified experimentally, approved and fixed in the theoretical base.
Classification of substances
The basis for the division of compounds into groups can be laid on many different signs. For example, the state of aggregation. All of them can be on this factor of four types:
- plasma;
- gas;
- liquid;
- crystalline substance (solid).
If we take as a basis a more "deeper" sign, then all substances can be divided into:
- organic - based on chains and cycles of carbon and hydrogen atoms;
- inorganic - everyone else.
According to the elemental composition, which reflect the formulas of substances, all of them are:
- simple - from one type of chemical atom;
- complex - two or more different types of elements.
In turn, simple are divided into metals and non-metals. Complexes have many classes: salts, bases, acids, oxides, esters, hydrocarbons, alcohols, nucleic acids and so on.
Different types of compound formulas
What is a visual, that is, graphic, display of connections? Of course, these are formulas of substances. They are different. Depending on the species, the information contained in them about the molecule is also different. So, there are such options:
- Empirical, or molecular. Reflects the quantitative and qualitative composition of the substance. It includes the symbols that make up the elements and the index in the lower left corner of it, showing the amount of this atom in the molecule. For example, H 2 O, Na 2 SO 4 , AL 2 (SO 4 ) 3 .
- Electronic graphic. This formula shows the number of valence electrons for each element that is part of the compound. Therefore, by this option it is already possible to predict some chemical and physical properties of substances.
- In organic chemistry, it is customary to use complete and abbreviated structural formulas. They reflect the bonding order of atoms in molecules, in addition, clearly indicate the substance belongs to one or another class of compounds. And this allows you to accurately determine the specific type of molecule and to predict all interactions characteristic of it.
Therefore, chemical symbolism and correctly formulated formulas of compounds are the most important part of working with all known substances. These are the theoretical foundations every student in chemistry should know.
Physical properties
A very important characteristic is the physical properties of substances. What exactly belongs to this group?
- The state of aggregation under various conditions, including standard ones.
- Boiling points, melting, freezing, evaporation.
- Organoleptic characteristics: color, smell, taste.
- Solubility in water and other solvents (organic, for example).
- Density and fluidity, viscosity.
- Electrical and thermal conductivity, heat capacity.
- Electrical permeability.
- Radioactivity.
- Absorption and emission.
- Inductance.
There are also a number of indicators that are very important for a complete list reflecting the properties of substances. However, they are between physical and chemical. It:
- electrode potential ;
- type of crystal lattice;
- electronegativity;
- hardness and brittleness;
- ductility and ductility;
- volatility or volatility;
- biological effects on living organisms (poisonous, asphyxiating, neuroparalytic, neutral, favorable, etc.).
Often, these indicators are mentioned precisely when the chemical properties of substances are considered directly. However, you can specify them in the physical section, which will not be an error.
Chemical properties of substances
This group includes all possible types of interactions of the molecule in question with other simple and complex substances. That is, these are directly chemical reactions. For each type of compound, they are strictly specific. However, common group properties are distinguished for a whole class of substances.
For example, all acids are able to react with metals according to their position in the electrochemical series of metal stresses. Also, neutralization reactions with alkalis, interaction with insoluble bases are characteristic of all. However, concentrated sulfuric and nitric acids are special, since the products of their interaction with metals differ from those obtained as a result of reactions with other members of the class.
Each substance has a lot of chemical properties. Their amount is determined by the activity of the compound, that is, the ability to react with other components. There are highly reactive, there are almost inert. This is a strictly individual indicator.
Simple substances
These include those that consist of one type of atom, but a different number of them. For example, S 8, O 2, O 3, Au, N 2, P 4, CL 2, Ar and others.
The chemical properties of simple substances are reduced to the interaction with:
- metals;
- non-metals;
- water
- acids;
- alkalis and amphoteric hydroxides;
- organic compounds;
- salts;
- oxides;
- peroxides and anhydrides and other molecules.
Again, it should be pointed out that this is a narrowly specific characteristic for each specific case. Therefore, the physical and chemical properties of simple substances are considered individually.
Complex substances
This group includes compounds whose molecules are formed by two or more different chemical elements. The amount of each of them can be different. Here are some simple examples to understand:
- H 3 PO 4 ;
- K 3 [Fe (CN) 6 ];
- Cu (OH) 2 ;
- LiF;
- AL 2 O 3 and others.
Since they all belong to different classes of substances, it is impossible to distinguish common physical and chemical characteristics for all. These are specific properties, peculiar and individual in each case.
Inorganic substances
There are over 500 thousand of them today. There are both simple and complex. In total, several main classes of inorganic compounds that represent all their diversity can be distinguished.
- Simple substances are metals.
- Oxides
- Simple substances are non-metals.
- Noble or inert gases.
- Peroxides.
- Anhydrides.
- Volatile hydrogen compounds.
- Hydrides.
- Salt.
- Acids.
- Grounds.
- Amphoteric compounds.
Any representative of each of the classes has its own set of physicochemical properties that make it possible to distinguish it from other compounds and identify it.
Properties of Organic Substances
Organics is a branch of chemistry that studies compounds other than inorganic and their properties. Their structure is based on carbon atoms capable of connecting with each other in various structures:
- linear and branched chains;
- cycles
- aromatic rings;
- heterocycles.
Living organisms consist of just such compounds, because the basis of life is proteins, fats and carbohydrates. All of them are representatives of organic substances. Therefore, their properties are special. However, in any case, regardless of which molecule we are talking about, it will still be characterized by a certain set of physicochemical properties, which we have already mentioned.
What is living matter?
Living is called the substance from which the entire biomass of our planet is composed. That is, those organisms that make up life on it:
- bacteria and viruses;
- protozoa;
- plants;
- animals;
- mushrooms;
- people.
Since the main part of the compounds in the composition of a living creature is organic, it is precisely them that can be attributed to the group of living matter. However, not all. Only those without which the existence of representatives of the living biosphere is impossible. These are proteins, nucleic acids, hormones, vitamins, fats, carbohydrates, amino acids and others. The term "living matter" was introduced by Vernadsky, the founder of the doctrine of the planet's biosphere.
Properties of living matter:
- possession of energy with the possibility of its transformation;
- self-regulation;
- arbitrary movement;
- alternation of generations;
- extreme variety.
Crystals and metallic substances
Crystalline are all compounds having a certain type of structure of the spatial lattice. There are compounds with atomic, molecular or metallic crystal lattice. The properties of crystalline substances also differ depending on the type . Typical solid compounds in the form of finely or coarse crystals are various salts.
There are also simple substances with a similar structure, for example, diamond or graphite, precious and semiprecious stones, minerals, rocks. Their main properties:
- hardness;
- fragility;
- average melting and boiling points.
However, as always, each characteristic may not be suitable for everyone.
The metallic properties of a substance are manifested by metals and their alloys. For them, a set of common characteristics can be distinguished:
- ductility and ductility;
- high boiling points, melting;
- electrical and thermal conductivity;
- metallic luster.