- Characteristics of the gaseous state
- Lacks volume or shape
- Bad conductor of heat
- Reagents
- Small particles
- Interactions
- General law of the gaseous state
- Examples of gaseous state
- Gaseous elements
- Gaseous compounds
- References
The gaseous state is a state of aggregation of matter in which the particles are held together by weak interactions, being capable of moving in all directions of the container that contains them. Of all the physical states of matter, the gaseous one is the one that manifests the greatest freedom and chaos.
Gases exert pressure, carry heat, and are made up of all kinds of small particles. Our atmosphere and the air we breathe is a manifestation of the gaseous state here on Earth.
In smoke emanations, the behavior of gases can be observed before they are dispersed through the atmosphere. Source: Pexels.
Examples of gases are greenhouse gases, such as water vapor, carbon dioxide, methane, or ozone. The carbon dioxide that we exhale in our breath is another example of a gaseous substance.
The gaseous particles are bound by weak interactions and move through the container. It is observed that the particles of the liquid state are more united, and those of the solid closely united
Liquids and solids, for example, will not move to positions beyond their own material limits, a fact that gases do not. The smoke from the cigarettes, from the chimneys and from the towers, demonstrate for themselves how the gas rises and disperses through the environment without anything stopping it.
Characteristics of the gaseous state
Lacks volume or shape
The gaseous state is characterized by not having a defined shape or volume. If there are no boundaries to hold it back, it will spread throughout the atmosphere. Even like helium, it will escape out of Earth.
A gas can only take the shape imposed by a container. If a container is cylindrical, the gas will "be" shaped like a cylinder.
Bad conductor of heat
This state is also characterized by being a poor conductor of both heat and electricity. It is generally less dense compared to solid and liquid states.
Because most gases are colorless, such as oxygen and carbon dioxide, you can determine how much of them is in a container by measuring their pressure.
Reagents
Gases tend to be more reactive, with the exception of noble gases, than liquids or solids, which is why they are potentially dangerous, either due to fire hazards, or because they can easily enter the respiratory systems of individuals.
Small particles
The gaseous particles are also usually small, being atoms or simple molecules.
For example, hydrogen gas, H 2, is a very small molecule made up of two hydrogen atoms. We also have helium, He, whose atoms are even smaller.
Interactions
The interactions in the gaseous state are negligible. In this it differs enormously from the liquid and solid states, in which its particles are highly cohesive and strongly interact with each other. In the molecules that form the liquid and solid states, there is hardly a certain molecular vacuum between them.
The particles in the gaseous state are very far from each other, there is a lot of vacuum between them. It is no longer a vacuum on a molecular scale. The distance that separates them is so great that each particle in the gas is free, indifferent to its surroundings, unless in its chaotic trajectory it collides with another particle or against the wall of the container.
If it is assumed that there is no container, the vacuum between the gas particles can be filled by air, which pushes and drags the gas in the direction of its current. That is why air, which consists of a gaseous mixture, is capable of deforming and spreading gaseous substances through the sky, as long as they are not much denser than it.
General law of the gaseous state
The experimental study of the behavior and mechanics of gases derived in several laws (Boyle, Charles, Gay-Lussac) that are combined to be able to predict what the parameters of any gaseous system or phenomenon will be, that is, what will be its temperature, volume and pressure.
This general law has the following mathematical expression:
P = KT / V
Where K is a constant, P the pressure, V the volume, and T the temperature of the gas on a kelvin scale. Thus, knowing two variables (to say, P and V), the third can be solved, which would become the unknown (T).
This law allows us to know, for example, what the temperature of a gas, enclosed in a container of volume V, must be to exhibit a pressure P.
If we add the contribution of Amadeus Avogadro to this law, then we will have the ideal gas law, which also involves the number of particles, and with them the molar concentration of the gas:
P = nRT / V
Where n corresponds to the number of moles of the gas. The equation can be rewritten as:
P = cRT
Where c is the molar concentration of the gas (n / V). Thus, from a general law, the ideal law is obtained that describes how pressure, concentration, temperature and volume of an ideal gas are related.
Examples of gaseous state
Gaseous elements
The periodic table itself offers a good repertoire of examples of elements that occur on Earth as gases. Between them we have:
-Hydrogen
-Helium
-Nitrogen
-Oxygen
-Fluorine
-Chlorine
-Neon
-Argon
-Krypton
-Xenon
This does not mean that the other elements cannot become gaseous. For example, metals can transform into gases if they are subjected to temperatures higher than their respective boiling points. Thus, there may be gases from particles of iron, mercury, silver, gold, copper, zirconium, iridium, osmium; of any metal.
Gaseous compounds
In the following list we have some examples of gaseous compounds:
-Carbon monoxide, CO
Lewis structure of carbon monoxide
-Carbon dioxide, CO 2 (gas that makes up our exhalations)
-Ammonia, NH 3 (vital substance for endless industrial processes)
-Sulfur trioxide, SO 3
-Methane, CH 4 (domestic gas, with which it is cooked)
Methane structure
-Ethane, CH 3 CH 3
-Nitrogen dioxide, NO 2 (brown gas)
-Phosgene, COCl 2 (highly poisonous substance)
-Air (being a mixture of nitrogen, oxygen, argon and other gases)
-Water vapor, H 2 O (which is part of clouds, geysers, machine vaporizers, etc.).
-Acetylene, HC≡CH
Acetylene structural formula
-Iodine vapors, I 2 (purple gas)
-Sulfur hexafluoride, SF 6 (very dense and heavy gas)
-Hydrazine, N 2 H 4
-Hydrogen chloride, HCl (which when dissolved in water produces hydrochloric acid)
References
- Whitten, Davis, Peck & Stanley. (2008). Chemistry (8th ed.). CENGAGE Learning.
- Wikipedia. (2020). Gas. Recovered from: en.wikipedia.org
- Edward A. Mason. (February 6, 2020). Gas. Encyclopædia Britannica. Recovered from: britannica.com
- Helmenstine, Anne Marie, Ph.D. (February 11, 2020). Gas Definition and Examples in Chemistry. Recovered from: thoughtco.com
- Maria Estela Raffino. (February 12, 2020). What is the gaseous state? Recovered from: concept.de