Surely you have ever heard the concept of laws of thermodynamicsAlso known as the principles of thermodynamics, these laws form the fundamental basis of physics related to the behavior of heat, energy, and entropy in thermodynamic systems. In this article, we will explain in detail everything you need to know about the four laws of thermodynamics, how they work, their origin, and their application in daily life.
Laws of thermodynamics
There are four laws of thermodynamics, numbered zero through three. These laws are used to describe how physical systems in our universe work and what limitations exist on energy processes. They are crucial to understanding such important phenomena as heat transfer, thermal equilibrium, and the growth of entropy, which is the degree of disorder in a system.
Each of these laws has a specific focus. Although the order of formulation was not chronological, they currently follow a logical structure that helps to understand energy interactions more clearly. Let's describe each of these laws and how they are applied in practice.
First Law of Thermodynamics
The first law of thermodynamics, also called law of conservation of energy, states that energy cannot be created or destroyed, only transformed. Simply put, the total amount of energy in an isolated system remains constant, even though it may change form.
For example, if you supply a quantity of energy in the form of heat to a system, the increase in total energy will be equal to the sum of the work done plus the increase in its internal energy. This law is fundamental to modern energy applications, from internal combustion engines to the production of electricity in thermodynamic plants.Practical example: Imagine an airplane engine. The fuel reacts chemically, releasing energy in the form of heat, some of which is converted into work to turn the propellers. Although some of this energy is dissipated as heat to the environment, the total energy is conserved, it just changes from one form to another.
Second law of thermodynamics
The second law of thermodynamics is also known as the law of entropyThis law states that all systems tend toward a state of greater disorder or entropy. As time passes, the entropy of the universe always increases.
This means that in any energy process, some of the energy is always dissipated as heat, causing systems to naturally move towards more disordered states. A system can never be 100% efficient, since there will always be a loss of usable energy.
Epractical example: If you burn a piece of paper, the matter is transformed into gases and ashes that cannot be recovered. This process is irreversible, as the paper cannot return to its original state. This is where the second law reveals that the disorder (entropy) of the system has increased.
Furthermore, this law helps explain why phenomena such as perpetual motion are impossible. There is always a loss of energy to the surroundings, which prevents a machine from running forever without an external source of energy.
Third law of thermodynamics
The third law of thermodynamics states that, upon reaching the Absolute zero, the entropy of a system tends to be minimal and constant. Absolute zero is the lowest possible temperature, equivalent to -273.15 °C or 0 K on the Kelvin scale.
In theory, at this temperature, particles in a system stop moving, removing all thermal energy from the system. However, reaching absolute zero is, in practice, impossible. As we approach this temperature, systems undergo drastic changes in their properties. For example, some materials experience phenomena such as superconductivity or superfluidity.
Practical application: Although absolute zero cannot be reached, research in physics has led to the creation of technologies that take advantage of the phenomena of materials at close temperatures, such as superconductors, which almost completely eliminate electrical resistance.
Zero law of thermodynamics
The Zeroth Law of Thermodynamics is the most recent law to be formulated, but it is crucial to the foundation of the others. This law states that if two systems are in thermal equilibrium with a third system, then those two systems are also in thermal equilibrium with each other. This means that if there is no heat transfer between them, then they have the same temperature.
Practical example: A thermometer placed in a glass of water measures the temperature of the liquid. When the thermometer reaches the same temperature as the water, it stops exchanging heat with the water. This is a classic example of the zeroth law at work.
Thanks to this law, we can define and measure the temperature of objects, which is essential for all thermodynamic physics.
Technical importance: Without the zeroth law, we could not establish the concept of temperature, nor use devices such as thermometers to measure thermal energies.
This set of four laws allows us to understand how energy works in our universe, how it is transferred, and how some of it is inevitably lost as entropy. Without these laws, many modern technological advances, such as engines, power plants, and cooling systems, would not be possible.