In the field of thermodynamics there are laws (or principles) that are focused on issues such as entropy, energy and temperature associated with a thermodynamic system that is in equilibrium.
The principles of thermodynamics refer to four statements focused on physical quantities that are essential to establish the characteristics of a thermodynamic system . These statements refer to entropy , energy and temperature , key issues to analyze the behavior of one of these systems under certain circumstances.
Before delving into these contents, it is very important to be clear that thermodynamics is the name given to a specialty within Physics that focuses its attention on work, temperature and heat , linking these magnitudes together and associating them with other issues. characteristic of the matter. Thermodynamic process , meanwhile, is understood as any variation evident in the state of a certain system, while the notion of thermodynamic equilibrium is applied every time a system, influenced by some environmental conditions, changes its state of being. spontaneous way. Knowing what the state variables (or thermodynamic variables ) are helps to better understand the topic. If we take a gas as a reference, then the references to consider will be pressure, volume, temperature and mass .
What are the principles of thermodynamics
Below we will describe what the principles of thermodynamics are and add data of interest that contribute to a better understanding of the meaning and applications of each one.
Firstly, the so-called zeroth law of thermodynamics appears. In this case, emphasis is placed on temperature (not to measure it but in order to provide a parameter), suggesting that if there is a pair of thermodynamic systems or bodies that, independently, are in thermal equilibrium with another system, then between Yes, thermal balance must also occur.
The first principle of thermodynamics , for its part, is intended for the conservation of energy . It indicates that, by accumulating internal energy , a closed system is capable of carrying out an exchange of energy with its environment in the form of both heat transfer and the performance of mechanical work.
There is also a second principle of thermodynamics , in which heat exchange and entropy gain notoriety. This statement leads towards the irreversibility of physical phenomena. It also leads to the conclusion that, in an isolated system , there will only be a chance that the entropy remains constant (if there is a reversible process) or increases.
Just as there are multiple types of thermometers, various temperature scales are recognized, among which the degree Kelvin and the famous Celsius can be linked.
In last place is the third principle of thermodynamics , which for many experts should not be valued as a law but rather it is more precise to mention it as Nernst's postulate . Beyond this, the content explains that, if there are a finite number of stages, it is not possible to achieve absolute zero since, in that case, all kinds of processes linked to a physical system are stopped in addition to registering, in that instance , an accelerated and minimum value of entropy (which, in a substance with crystalline and pure characteristics, becomes null in the position of absolute zero).
After citing multiple concepts, it is necessary to report on a property of thermodynamic systems : state functions . Within this set are entropy and internal energy , but mechanical work and heat are not part of it.
Gas thermodynamics
The study of gas thermodynamics calls for examining their behavior in the face of variations in energy , pressure , volume and temperature .
In this context, the ideal gas law gains notoriety based on the equation of state of the so-called ideal gas together with the bases of the kinetic theory of gases . Likewise, when adding details in this regard, the Boyle-Mariotte law (detailing an isothermal process ), the Gay-Lussac law (about the isochoric process ) and Charles's law ( isobaric process ) appear as issues to consider. As a complement, it is advisable to know in detail what Avogadro's law says and what it is for without leaving the kinetic theory of gases in the background.
It should also be noted that, when working with fluids, the Van der Waals equation must be available as a resource.
A black body that is in thermodynamic equilibrium emits thermal radiation. This type of radiation is one of the main ways of heat transfer.
Value of the principles of thermodynamics
The value of the principles of thermodynamics lies in their importance in understanding how energy transformations and exchanges develop, and with what particularities, in a thermodynamic process .
These laws clarify doubts, provide answers and have numerous fields of application or use. Just by thinking about the influence of temperature and its variations, we can cite as examples the need to preserve food products in a refrigerator (or refrigerator) to keep them in good condition through refrigeration or the use of air conditioning equipment to generating a cool environment in a closed environment during days of extreme heat or the other way around: the intention of turning on the heating in homes, educational establishments and other places when it is very cold. Even using a thermometer to check body temperature is connected to these principles that emphasize thermal balance and heat transfer , for example.