Gaseous substances: examples and properties

To date, it is known about the existence ofmore than 3 million different substances. And this figure is growing every year, as synthetic chemists and other scientists are constantly making experiments to obtain new compounds that have some useful properties.

Some of the substances are natural inhabitants,formed naturally. The other half are artificial and synthetic. However, in the first and second cases, a considerable part is made up of gaseous substances, examples and characteristics of which we will consider in this article.

Aggregate states of substances

Since the XVII century, it was accepted that allknown compounds can exist in three aggregate states: 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 one more form. This is plasma.

What is it? These are partially or completely ionized gases. And it turns out, such substances in the universe is the vast majority. Thus, it is in the state of the plasma that:

• interstellar matter;
• space matter;
• higher layers of the atmosphere;
• nebulae;
• 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, to make it turn into ions.

Gaseous substances: examples

Examples of the substances under consideration areweight. After all, gases are known since the XVII century, when van Helmont, naturalist, first received carbon dioxide and began to explore its properties. By the way, he also gave the name to this group of compounds, because, in his opinion, gases are something disorderly, chaotic, connected with spirits and something invisible, but palpable. This name has caught on in Russia.

You can classify all the gaseous substances, then the examples will be easier to produce. After all, to embrace all the diversity is difficult.

The composition is distinguished:

• simple,
• complex molecules.

The first group includes those that consist of identical atoms in any number of them. Example: Oxygen - O₂, ozone - O₃, hydrogen-H₂, chlorine - CL₂, fluorine-F₂, nitrogen - N₂ and others.

The second category should include such compounds, which include several atoms. This will be gaseous complex substances. Examples are:

• hydrogen sulphide - H₂S;
• hydrochloric acid - HCL;
• methane - CH_4;
• sulfur dioxide - SO₂;
• brown gas - NO₂;
• Freon - CF₂CL₂;
• ammonia - NH₃ and others.

Classification by nature of substances

It is also possible to classify types of gaseous substances as belonging to the organic and inorganic world. That is, by the nature of the atoms. Organic gases are:

• the first five representatives of the ultimate hydrocarbons (methane, ethane, propane, butane, pentane). The general formula C_nH_{2n + 2};
• Ethylene-C₂H₄;
• acetylene or ethyne-C₂H₂;
• methylamine-CH₃NH₂ and others.

To the category of gases of inorganic nature are chlorine, fluorine, ammonia, carbon monoxide, silane, gassing gas, inert or noble gases and others.

Another classification, which can besubject to the compounds under consideration, is a fission based on the constituent particles. It is from the atoms that not all gaseous substances are composed. Examples of structures in which ions, molecules, photons, electrons, Brownian particles, and plasma are present are also related to compounds in such an aggregate state.

Properties of gases

Characteristics of substances in the consideredstate are different from those for solid or liquid compounds. The thing is that the properties of gaseous substances are special. Their particles are easily and rapidly mobile, the substance as a whole is isotropic, that is, the properties are not determined by the direction of motion of the structures that make up the structure.

It is possible to designate the most important physical properties of gaseous substances, which will distinguish them from all other forms of existence of matter.

1. These are such connections that can not be seen andto control, to feel by ordinary human means. To understand the properties and to identify a particular gas, based on all four describe their parameters: pressure, temperature, amount of substance (mole) amount.
2. Unlike liquids, gases can occupy the entire space without a residue, limited only to the size of the vessel or room.
3. All gases mix easily with each other, and these compounds do not have an interface.
4. There are lighter and heavier representatives, so under the influence of gravity and time, it is possible to see their separation.
5. Diffusion is one of the most important properties of these compounds. The ability to penetrate into other substances and saturate them from within, while doing completely disordered movements within their structure.
6. Real electric current can not conduct real gases, but if we talk about rarefied and ionized substances, then the conductivity increases sharply.
7. The heat capacity and thermal conductivity of the gases are low and fluctuates in different species.
8. Viscosity increases with increasing pressure and temperature.
9. There are two variants of the interphase transition: evaporation - the liquid turns into vapor, sublimation - a solid, bypassing the liquid, becomes gaseous.

A distinctive feature of vapors from true gasesin that the former under certain conditions are capable of passing into a liquid or a solid phase, while the latter are not. It should also be noted the ability of the compounds under consideration to resist deformations and to be fluid.

Similar properties of gaseous substances allowwidely apply them in various fields of science and technology, industry and the national economy. In addition, specific characteristics are strictly individual for each representative. We have considered only common features of all real structures.

Compressibility

At different temperatures, and also under the influence ofpressures of gases are able to contract, increasing their concentration and decreasing the volume occupied. At elevated temperatures, they expand, at low temperatures they contract.

Under the influence of pressure, changes also occur. The density of gaseous substances increases and, upon reaching a critical point, which for each representative has its own, a transition to another aggregate state may occur.

The main scientists who contributed to the development of the theory of gases

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 managed to make the most significant discoveries.

1. In 1811, Amedeo Avogadro made a discovery. It does not matter what gases, the main thing is that under the same conditions they are in the same volume they contain an equal number of molecules. There is a calculated value, named after the name of the scientist. It is equal to 6.03 * 10²³ molecules for 1 mole of any gas.
2. Fermi - created the theory of an ideal quantum gas.
3. Gay-Lussac, Boyle-Marriott - the names of scientists who created the basic kinetic equations for calculations.
4. Robert Boyle.
5. John Dalton.
6. Jacques Charles and many other scientists.

Structure of gaseous substances

The most important feature in the constructioncrystal lattice of the substances under consideration, is that in the nodes it is either atoms or molecules that are joined together by weak covalent bonds. Also there are forces of van der Waals interaction when it comes to ions, electrons and other quantum systems.

Therefore, the main types of lattice structure for gases are:

• Atomic;
• molecular.

The connections inside easily tear, so these connectionsdo 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, due to diffusion, they are able to penetrate into solids and occupy free cluster spaces inside them. The air is not passed through, the heat is retained. This is the basis for the use of gases and solids in aggregate for construction purposes.

Simple substances among gases

What are the structure and structure of gases refer toof this category, we have already mentioned above. These are the ones that consist of the same atoms. Examples can be given a lot, because a significant part of non-metals from the entire periodic system under ordinary conditions exists precisely in such an aggregate state. For example:

• phosphorus white - one of the allotropic modifications of this element;
• nitrogen;
• oxygen;
• fluorine;
• chlorine;
• helium;
• neon;
• argon;
• krypton;
• xenon.

The molecules of these gases can be either monatomic (noble gases) or polyatomic (ozone - O₃). The type of connection is covalent nonpolar, in most cases rather weak, but not at all. Crystalline lattice of molecular type, which allows these substances to easily move from one aggregate state to another. So, for example, iodine under normal conditions - dark purple crystals with metallic luster. However, when heated, they sublimate into bright-violet gas clouds - I₂.

By the way, any substance, including metals, under certain conditions can exist in a gaseous state.

Complex compounds of gaseous nature

Of these gases, of course, most. Different combinations of atoms in molecules, combined by covalent bonds and van der Waals interactions, allow hundreds of different representatives of the aggregate state under consideration to form.

Examples of complex substances among gases can be all compounds consisting of two or more different elements. This includes:

• propane;
• butane;
• acetylene;
• ammonia;
• silane;
• phosphine;
• methane;
• carbon disulfide;
• sulphur dioxide;
• brown gas;
• freon;
• ethylene and others.

Crystalline lattice of molecular type. Many of the representatives readily dissolve in water, forming the corresponding acids. Most of these compounds are an important part of chemical syntheses in industry.

Methane and its homologues

Sometimes the general notion of "gas" means naturalA useful mineral, which is a whole mixture of gaseous products of predominantly organic nature. It contains substances such 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, where people cook food that 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 is estimated at trillions of cubic meters, and this is quite justified.

Oxygen and carbon dioxide

What substances gaseous can be called the mostwidespread and famous even for first graders? The answer is obvious - oxygen and carbon dioxide. After all, it is they who are directly involved in the gas exchange that occurs in all living beings on the planet.

It is known that it is due to oxygen is possible.life, because only certain types of anaerobic bacteria are able to exist without it. And carbon dioxide is a necessary product of "nutrition" for all plants that absorb it in order to carry out the process of photosynthesis.

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 more often a reducing agent.

Halogens

This is a group of compounds in which atoms -These are particles of a gaseous substance that are connected in pairs to each other due to a covalent non-polar bond. However, not all halogens are gases. Bromine is a liquid under normal conditions, and iodine is an easily sublimated solid. Fluorine and chlorine are toxic substances hazardous to the health of living beings, which are the strongest oxidizers and are used in the synthesis very widely.