Gaseous substances: examples and properties

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

Some of the substances are natural inhabitants, which are 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 all known 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 are overwhelming. Thus, it is in the plasma state 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 are mass. 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 taken root in Russia.

You can classify all the gaseous substances, then the examples will be easier to produce. After all, to embrace all the variety 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 - 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. This will be gaseous complex substances. Examples are:

• Hydrogen sulphide - H ₂ S;
• Hydrochloric acid - HCL;
• Methane - CH _4;
• Sulfur dioxide - SO ₂ ;
• Brown gas - NO ₂ ;
• Freon - CF ₂ CL ₂ ;
• Ammonia - NH ₃ 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 is C _n H _{2n + 2} ;
• Ethylene - C ₂ H ₄ ;
• Acetylene or ethyne-C ₂ H ₂ ;
• Methylamine - CH ₃ NH ₂ 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 to which the compounds under consideration can be subjected is the 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 this state differ 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 compounds that can not be seen and controlled, felt by ordinary human means. To understand the properties and identify a particular gas, they rely on four parameters describing all of them: pressure, temperature, amount of substance (mole), volume.
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 are easily mixed together, 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, 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, passing the liquid, becomes gaseous.

A distinctive feature of vapors from true gases is that the former can under certain conditions become liquid or a solid phase, while the latter do 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 make it possible to widely apply them in the most diverse 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, as well as under the influence of pressure, gases are able to contract, increasing their concentration and decreasing the volume occupied. At elevated temperatures they expand, at low temperatures they contract.

Under pressure, changes also occur. The density of gaseous substances increases and, when a critical point is reached, 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, since 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 which gases, the main thing is that under identical conditions, they contain an equal number of molecules in the same volume. There is a calculated value, named after the name of the scientist. It is equal to 6.03 * 10 ²³ 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.

The structure of gaseous substances

The most important feature in the construction of the crystal lattice of the substances under consideration is that at 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 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, due to diffusion, they are able to penetrate into solids and occupy free cluster spaces inside them. The air is not allowed to pass through, the heat is retained. This is the basis for the use of gases and solids in aggregate for building purposes.

Simple substances among gases

What are the structure and structure of gases belong to this category, we have already discussed above. These are the ones that consist of the same atoms. Examples can be given a lot, because a significant part of nonmetals 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 - O ₃ ). The type of connection is covalent nonpolar, in most cases it is 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 - I ₂ .

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, united 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. Here you can include:

• 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 common notion of "gas" is a natural 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 that is the household gas in which 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 gaseous substances can be called the most widespread and known even first-graders? The answer is obvious - oxygen and carbon dioxide. After all, they are the 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 kinds of anaerobic bacteria can exist without it. And carbon dioxide is a necessary "food" product for all plants that absorb it for the purpose of carrying out the process of photosynthesis.

From a chemical point of view, both oxygen and carbon dioxide are important substances for synthesizing compounds. The first is a strong oxidizer, the second is more often a reducing agent.

Halogens

This is a group of compounds in which atoms are particles of a gaseous substance, connected in pairs by a covalent nonpolar 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 poisonous substances dangerous to the health of living things, which are the strongest oxidants and are used very widely in syntheses.