A real gas shows thermodynamic behavior.
The term in question is made up of two words of which we are going to first determine their etymological origin. Thus the word gas , which emanates from the Latin chaos that can be translated as "chaos", was a word created by the Belgian chemist Juan Batista Van Helmont.
On the other hand, we must emphasize that the adjective royal has its origins in the Latin language and specifically in the term rex, which can be translated as "king."
A fluid of small density is known as a gas . It is a condition of aggregation of certain subjects that leads them to expand indefinitely, because they do not have their own formats or volume . The gases, therefore, take on the volume and appearance of the bowl, jar or container that conserves them.
Real gas vs. ideal gas
It is interesting to mention that it is possible to distinguish between an ideal gas and another classified as real , according to the principles that relate its pressure , volume and temperature . The ideal gas is considered part of the group of theoretical gases because it is made up of point particles that move randomly and do not interact with each other.
The real gas, on the other hand, is one that has thermodynamic behavior and does not follow the same equation of state as ideal gases. Gases are considered real at high pressure and low temperature .
Under normal pressure and temperature conditions, however, real gases tend to behave qualitatively in the same way as an ideal gas. Therefore, gases such as oxygen , nitrogen , hydrogen or carbon dioxide can be treated as ideal gases under certain circumstances.
Helium is a real gas that has ideal-like behavior.
Van der Waals forces
All of this would lead us to have to mention what is known as the Van der Waals forces , which are those forces, both repulsive and attractive, that occur between molecules and that in the case of real gases are quite small. They are named after the scientist Johannes van der Waals, a Dutchman who won the Nobel Prize in Physics in 1910 and who became a reference thanks to them.
Likewise, from those, what is known as Van der Waals' Law was also established, which is defined as an equation of state that originates from what is the ideal gas law. In it, the pressure of the gas, the number of moles that is equivalent to the amount of substance, the universal gas constant or the volume occupied by the gas take center stage. And all this without forgetting what is known as temperature in absolute value.
Real gas equations
To measure the behavior of a gas that differs from the usual conditions of the ideal gas, it is necessary to apply the real gas equations. These show that real gases do not have infinite expansion : otherwise, they would reach a state in which they could no longer occupy a larger volume.
The behavior of a real gas resembles that of an ideal gas when its chemical formula is simple and when its reactivity is low. Helium , for example, is a real gas whose behavior is close to ideal.