Today, there are about 2.5 million various compounds of both natural origin and artificially synthesized by man. All of them are very different, some of them are irreplaceable participants in biological processes occurring in living organisms. Compounds are distinguished from each other by the properties of substances. Characteristics and what else allows you to identify a particular chemical molecule, we will consider further.
What is a substance?
If you define this concept, you need to point out its connection with physical bodies. After all, it is customary to consider the substance of which these bodies are composed. So, glass, iron, sulfur, wood are substances. Examples can be given endlessly. It is easier to understand the following: the term under consideration refers to all the variety of different combinations of molecules that exist in the world, as well as simple monatomic particles.
Thus, water, alcohol, acids, alkalis, proteins, carbohydrates, s alt, sugar, sand, clay, diamond, gases, and so on - these are all substances. Examples allow you to more clearly capture 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 thatis made of glass, and the sheet of paper is the body, which is processed pulp or wood.
Of course, all molecules are different. What underlies their difference 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 many more diverse ones. For example, the science of chemistry uses for each substance, or rather, for its identification, its reagent. 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 division of compounds into groups can be based on many different features. For example, aggregate state. All of them can be of four types according to this factor:
- plasma;
- gas;
- liquid;
- crystalline substance (solid).
If we take as a basis a more "deep" feature, 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. Compounds have many classes: s alts, bases, acids, oxides, esters, hydrocarbons, alcohols, nucleic acids, and so on.
Different types of compound formulas
What is a visual, that is, graphical, 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 also differs. So, there are such options:
- Empirical, or molecular. Reflects the quantitative and qualitative composition of the substance. It includes the symbols of the constituent elements and an index in the lower left corner of it, showing the amount of this atom in the molecule. For example, N2O, Na2SO4, AL2 (SO4)3.
- Electronic graphics. This formula shows the number of valence electrons for each element that makes up the compound. Therefore, according to this option, it is already possible to predict some chemical and physical properties of substances.
- In organic chemistry, it is customary to use full and abbreviated structural formulas. They reflect the order of bonding of atoms in molecules, in addition, they clearly indicate the belonging of a substance to a particular class of compounds. And this allows you to accurately determine the specific type of molecule and predict all the interactions characteristic of it.
Therefore, chemical symbolism and correctly composed formulas of compounds are the most important part of working with all known substances. These are the theoretical foundations you need to knowevery chemistry student.
Physical properties
A very important characteristic is the manifested physical properties of substances. What belongs to this group?
- Aggregate state under various conditions, including standard ones.
- Boiling, melting, freezing, evaporation temperatures.
- 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 that reflects the properties of substances. However, they are between physical and chemical. This is:
- electrode potential;
- type of crystal lattice;
- electronegativity;
- hardness and brittleness;
- ductility and ductility;
- volatility or volatility;
- biological effects on living organisms (poisonous, suffocating, nerve paralytic, neutral, beneficial, etc.).
Often these indicators are mentioned precisely when the chemical properties of substances are already considered directly. However, you can also specify them in the physical section, which will not be a mistake.
Chemical properties of substances
This group includesall possible types of interactions of the considered molecule with other simple and complex substances. That is, these are directly chemical reactions. For each type of connection, they are strictly specific. However, common group properties are distinguished for a whole class of substances.
For example, all acids are capable of reacting with metals according to their position in the electrochemical series of metal voltages. Also, all are characterized by neutralization reactions with alkalis, interaction with insoluble bases. 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 number is determined by the activity of the compound, that is, the ability to react with other components. There are highly reactive, there are practically inert. This is strictly an individual indicator.
Simple substances
These include those that consist of the same type of atoms, but of different numbers. For example, S8, O2, O3, Au, N2, P4, CL2, Ar and others.
The chemical properties of simple substances are reduced to interaction with:
- metals;
- non-metals;
- water;
- acids;
- alkalis and amphoteric hydroxides;
- organic compounds;
- s alts;
- oxides;
- peroxides and anhydrides and othersmolecules.
Again, it should be pointed out that this is a highly 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 number of each of them can be different. For understanding, here are a few simple examples:
- H3PO4;
- K3[Fe(CN)6];
- Cu(OH)2;
- LiF;
- AL2O3 and others.
Since they all belong to different classes of substances, it is impossible to single out common physical and chemical characteristics for all. These are specific properties, peculiar and individual in each case.
Inorganic substances
Today there are over 500 thousand of them. There are both simple and complex. In total, several main classes of inorganic compounds can be distinguished, which represent all their diversity.
- Simple substances metals.
- Oxides.
- Simple substances non-metals.
- Noble or inert gases.
- Peroxides.
- Anhydrides.
- Volatile hydrogen compounds.
- Hydrides.
- S alts.
- Acids.
- Foundations.
- Amphoteric compounds.
Any representative of each class has its own set of physicalchemical properties that allow it to be distinguished from other compounds and identified.
Properties of organic substances
Organics is a branch of chemistry that deals with the study of compounds other than inorganic and their properties. Their structure is based on carbon atoms that can combine 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, no matter what kind of molecule we are talking about, it will still be characterized by a certain set of physico-chemical properties that we have already mentioned before.
What is living matter?
Living is 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;
- simple;
- plants;
- animals;
- mushrooms;
- people.
Since the main part of the compounds in the composition of a living being 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 introducedVernadsky, 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;
- free movement;
- alternation of generations;
- extreme variety.
Crystals and metallic substances
Crystalline refers to all compounds that have a certain type of spatial lattice structure. There are compounds with an atomic, molecular or metallic crystal lattice. Depending on the type, the properties of crystalline substances also differ. Typical solid compounds in the form of finely or coarsely dispersed crystals are various s alts.
There are also simple substances with a similar structure, such as diamond or graphite, precious and semi-precious stones, minerals, rocks. Their main properties:
- hardness;
- fragility;
- average melting and boiling points.
However, as always, every characteristic may not be right for everyone.
Metallic properties of a substance are shown by metals, their alloys. For them, a set of common characteristics can be distinguished:
- ductility and ductility;
- high boiling point, melting point;
- electrical and thermal conductivity;
- metallic luster.
