Today, more than 3 million different substances are known to exist. And this figure is growing every year, since synthetic chemists and other scientists are constantly making experiments to obtain new compounds with any useful properties.
Some of the substances are natural inhabitants that form naturally. The other half is artificial and synthetic. However, in the first and second cases, a significant part is made up of gaseous substances, the examples and characteristics of which we will consider in this article.
Aggregate states of substances
Since the 17th century, it was commonly believed that all known compounds are able to exist in three states of aggregation: solid, liquid, gaseous substances. However, careful studies of recent decades in the field of astronomy, physics, chemistry, space biology and other sciences have proved that there is another form. This is plasma.
What is she like? These are partially or fully ionized gases. And it turns out that the vast majority of such substances in the universe. So, it is in a plasma state that:
- interstellar matter;
- cosmic matter;
- higher layers of the atmosphere;
- nebulae;
- the composition of many planets;
- stars.
Therefore, today they say that there are solid, liquid, gaseous substances and plasma. By the way, each gas can be artificially transferred to such a state if it is subjected to ionization, that is, it is forced to turn into ions.
Gaseous Substances: Examples
Examples of the substances in question can be given a lot. After all, gases have been known since the 17th century, when van Helmont, a natural scientist, first received carbon dioxide and began to study its properties. By the way, he also gave the name to this group of compounds, since, in his opinion, gases are something disordered, chaotic, associated with perfumes and something invisible, but tangible. This name has taken root in Russia.
All gaseous substances can be classified; then it will be easier to give examples. After all, covering all the diversity is difficult.
The composition is distinguished:
The first group includes those that consist of the same atoms in any quantity. Example: oxygen - O 2 , ozone - O 3 , hydrogen - H 2 , chlorine - CL 2 , fluorine - F 2 , nitrogen - N 2 and others.
The second category should include such compounds, which include several atoms. These will be gaseous complex substances. Examples are:
- hydrogen sulfide - H 2 S;
- hydrogen chloride - HCL;
- methane - CH 4;
- sulfur dioxide - SO 2 ;
- brown gas - NO 2 ;
- Freon - CF 2 CL 2 ;
- ammonia - NH 3 and others.
Classification by the nature of substances
It is also possible to classify the types of gaseous substances according to their belonging to the organic and inorganic world. That is, by the nature of the constituent atoms. Organic gases are:
- the first five representatives of saturated hydrocarbons (methane, ethane, propane, butane, pentane). General formula C n H 2n + 2 ;
- ethylene - C 2 H 4 ;
- acetylene or ethine - C 2 H 2 ;
- methylamine - CH 3 NH 2 and others.
Inorganic gases include chlorine, fluorine, ammonia, carbon monoxide, silane, laughing gas, inert or noble gases, and others.
Another classification that can be subjected to the compounds in question is fission based on the constituent particles. It is from atoms that not all gaseous substances are composed. Examples of structures in which ions, molecules, photons, electrons, Brownian particles, plasma are present also apply to compounds in such an aggregate state.
Gas properties
The characteristics of substances in the state under consideration differ from those for solid or liquid compounds. The thing is that the properties of gaseous substances are special. Their particles are easily and quickly mobile, the substance as a whole is isotropic, that is, the properties are not determined by the direction of movement of the structures included in the composition.
You can identify the most important physical properties of gaseous substances, which will distinguish them from all other forms of the existence of matter.
- These are compounds that cannot be seen and controlled, felt in ordinary human ways. To understand the properties and identify a particular gas, they rely on four parameters that describe them all: pressure, temperature, amount of substance (mol), volume.
- Unlike liquids, gases are able to occupy the entire space without residue, being limited only by the size of the vessel or room.
- All gases are easily mixed with each other, while these compounds do not have an interface.
- There are lighter and heavier representatives, therefore, under the influence of gravity and time, it is possible to see their separation.
- Diffusion is one of the most important properties of these compounds. The ability to penetrate into other substances and saturate them from the inside, while making completely disordered movements within its structure.
- Real gases cannot conduct electric current, but if we talk about rarefied and ionized substances, then the conductivity increases sharply.
- The heat capacity and thermal conductivity of gases is low and varies in different species.
- Viscosity increases with increasing pressure and temperature.
- There are two options for the interphase transition: evaporation - the liquid turns into steam, sublimation - a solid, bypassing the liquid, becomes gaseous.
A distinctive feature of vapors from true gases is that the former, under certain conditions, are capable of passing into a liquid or solid phase, while the latter do not. It should also be noted the ability of the considered compounds to resist deformation and to be fluid.
Such properties of gaseous substances allow their wide application in various fields of science and technology, industry and the national economy. In addition, the specific characteristics are strictly individual for each representative. We considered only features common to all real structures.
Compressibility
At different temperatures, as well as under the influence of pressure, the gases are able to compress, increasing their concentration and reducing the volume occupied. At elevated temperatures they expand, at low temperatures they contract.
Pressure also changes. The density of gaseous substances increases and, upon reaching a critical point, which is different for each representative, a transition to another state of aggregation can occur.
Key Scientists Contributing to the Development of the Gas Doctrine
There are many such people, because the study of gases is a laborious and historically long process. Let us dwell on the most famous personalities who have managed to make the most significant discoveries.
- Amedeo Avogadro in 1811 made a discovery. It does not matter which gases, the main thing is that under the same conditions they contain an equal amount of them in the same volume in the number of molecules. There is a calculated value having a name by the name of the scientist. It is equal to 6.03 * 10 23 molecules for 1 mol of any gas.
- Fermi - created the doctrine of the ideal quantum gas.
- Gay-Lussac, Boyle-Marriott - the names of scientists who created the basic kinetic equations for calculations.
- Robert Boyle
- John Dalton.
- Jacques Charles and many other scientists.
The structure of gaseous substances
The most important feature in constructing the crystal lattice of the substances under consideration is that its nodes are either atoms or molecules that are joined together by weak covalent bonds. There are also van der Waals forces when it comes to ions, electrons, and other quantum systems.
Therefore, the main types of gratings for gases are:
The bonds inside easily break, so these compounds do not have a constant shape, but fill the entire spatial volume. This also explains the lack of electrical conductivity and poor thermal conductivity. But the thermal insulation of gases is good, because, thanks to diffusion, they are able to penetrate into solids and occupy free cluster spaces inside them. Air is not allowed, heat is retained. This is the basis for the use of gases and solids in the aggregate for construction purposes.
Simple substances among gases
What gases are in this category in terms of structure and structure, we have already discussed above. These are those that are made up of identical atoms. There are many examples, because a significant part of non-metals from the entire periodic system under ordinary conditions exists in such an aggregate state. For instance:
- white phosphorus - one of the allotropic modifications of this element;
- nitrogen;
- oxygen;
- fluorine;
- chlorine;
- helium;
- neon;
- argon;
- krypton;
- xenon.
The molecules of these gases can be both monatomic (noble gases) and polyatomic (ozone - O 3 ). The type of bond is covalent non-polar, in most cases rather weak, but not at all. The crystal lattice is molecular type, which allows these substances to easily transfer from one state of aggregation to another. So, for example, iodine under ordinary conditions - dark violet crystals with a metallic luster. However, when heated, they sublimate into clubs of bright violet gas - I 2 .
By the way, any substance, including metals, under certain conditions can exist in a gaseous state.
Complex compounds of gaseous nature
Such gases, of course, are the majority. Various combinations of atoms in molecules, combined by covalent bonds and van der Waals interactions, allow hundreds of different representatives of the considered aggregate state to form.
Examples of precisely complex substances among gases can be all compounds consisting of two or more different elements. This may include:
- propane;
- butane;
- acetylene;
- ammonia;
- silane;
- phosphine;
- methane;
- carbon disulfide;
- sulphur dioxide;
- brown gas;
- freon;
- ethylene and others.
Crystal lattice of molecular type. Many of the representatives are easily soluble in water, forming the corresponding acid. Most of these compounds are an important part of chemical syntheses carried out in industry.
Methane and its homologues
Sometimes the general concept of "gas" means a natural mineral, which is a whole mixture of gaseous products of predominantly organic nature. It contains such substances as:
- methane;
- ethane;
- propane;
- butane;
- ethylene;
- acetylene;
- pentane and some others.
In industry, they are very important, because it is the propane-butane mixture - this is a household gas, on which people cook food, which is used as a source of energy and heat.
Many of them are used for the synthesis of alcohols, aldehydes, acids and other organic substances. The annual consumption of natural gas amounts to trillions of cubic meters, and this is entirely justified.
Oxygen and Carbon Dioxide
What gaseous substances can be called the most widespread and known even to first graders? The answer is obvious - oxygen and carbon dioxide. After all, it is they who are direct participants in the gas exchange that occurs in all living beings on the planet.
It is known that it is thanks to oxygen that life is possible, since only some types of anaerobic bacteria can exist without it. And carbon dioxide is a necessary “food” product for all plants that absorb it in order to carry out the photosynthesis process.
From a chemical point of view, both oxygen and carbon dioxide are important substances for the synthesis of compounds. The first is a strong oxidizing agent, the second is often a reducing agent.
Halogens
This is such a group of compounds in which atoms are particles of a gaseous substance, connected in pairs by a covalent non-polar bond. However, not all halogens are gases. Bromine is a liquid under normal conditions, and iodine is a readily sublimated solid. Fluorine and chlorine are poisonous substances dangerous to the health of living things, which are the strongest oxidizing agents and are used very widely in syntheses.