What is Thermodynamics ?

(ORDO NEWS) — Thermodynamics is the branch of physics that deals with the relationship between heat and other forms of energy. In particular, it describes how thermal energy is converted into other forms of energy and how thermal energy affects matter. Let’s take a closer look at the laws of thermodynamics.


Thermodynamics is concerned with several properties of matter; the main one is warmth. According to Georgia State University, heat is energy transferred between substances or systems due to temperature differences between them.

As a form of energy, heat is conserved – it cannot be created or destroyed. However, it can be transferred from one body to another. Heat can also be converted into other forms of energy.


According to Georgia State University, the amount of heat transferred by a substance depends on the speed and number of atoms or molecules of that substance in motion.

The faster the atoms or molecules move, the higher the temperature, and the more atoms or molecules are in motion, the more heat they transfer.

Temperature is a measure of the average kinetic energy of particles in a sample of matter, expressed in units or degrees, indicated by a standard scale. The most commonly used temperature scale is Celsius, which is based on the freezing and boiling points of water, assigning values ​​of 0 C and 100 C respectively.

The Fahrenheit scale is also based on the freezing and boiling points of water, which are assigned values ​​of 32 degrees Fahrenheit and 212 F, respectively.

However, scientists around the world use the Kelvin scale, named after William Thomson, because it is based on total heat energy rather than the freezing and boiling points of water.

This scale uses the same increments as the Celsius scale; for example, a change in temperature per 1 C is equal to 1 K. However, the Kelvin scale starts at absolute zero, the temperature at which there is a complete absence of thermal energy and all molecular motion stops. 0 K is minus 459.67 F or minus 273.15 C.

What is thermodynamics 2

Heat transfer

Heat can be transferred from one body to another or between the body and the environment in various ways: conduction, convection.

Conduction is the transfer of energy through a solid material. Conduction between bodies occurs when they are in direct contact and molecules transfer their energy through the interface.

Convection is the transfer of heat into or out of a liquid medium. Molecules in a gas or liquid in contact with a solid transfer or absorb heat to or from that body and then move away, allowing other liquid molecules to move into place and repeat the process.


All thermodynamic systems generate waste heat. This waste leads to an increase in entropy, which is a measure of the disorder of the system. Because work comes from ordered molecular motion, entropy is a measure of the energy that is not available to do work.

Entropy in any closed system always increases; it never decreases. In addition, moving parts produce waste heat due to friction, and radiant heat inevitably flows out of the system.

This makes the so-called perpetual motion machines impossible. Siabal Mitra, professor of physics at the University of Missouri, said: “You can’t build an engine that is 100% efficient, which means you can’t build a perpetual motion machine.

However, there are many people who still don’t believe in it, and also those who are still trying to build perpetual motion machines.”

Entropy is also defined as “a measure of disorder or randomness in a closed system” that also increases inexorably.

You can mix hot and cold water, but because a large cup of warm water is more disordered than two small cups containing hot and cold water, you can never separate it back into hot and cold without adding energy to the system. In other words, you can’t take apart an egg or remove the cream from your coffee.

Four laws of thermodynamics

The fundamental principles of thermodynamics were originally expressed in three laws. Scientists later found that a more fundamental law had been neglected, presumably because it seemed so obvious that it didn’t need to be stated explicitly.

In order to form a complete set of rules, the scientists decided that this most fundamental law needed to be included. The problem, however, was that the first three laws had already been established and were well known by their assigned numbers.

Faced with the prospect of renumbering existing laws, which would cause considerable confusion, or putting a prominent law at the end of the list, which would not make logical sense, British physicist Ralph H. Fowler proposed an alternative that solved the dilemma: he called the new law “Law Zero.” according to Saint Anselm’s College.

– The zeroth law of thermodynamics states that if two bodies are in thermal equilibrium with some third body, then they are also in equilibrium with each other. This establishes temperature as a fundamental and measurable property of matter.

– The first law of thermodynamics states that the total increase in the energy of a system is equal to the increase in thermal energy plus the work done on the system. This states that heat is a form of energy and therefore obeys the principle of conservation, i.e. it can neither be created nor destroyed.

– The second law of thermodynamics states that heat energy cannot be transferred from a body at a lower temperature to a body at a higher temperature without adding energy. That’s why running an air conditioner costs decent money.

– The third law of thermodynamics states that the entropy of an ideal crystal—that is, a substance made up of atoms arranged in a perfectly ordered, symmetrical order—is zero at absolute zero. As explained above, entropy is sometimes referred to as “waste energy”, or energy that is unable to do work; and since there is no heat energy at absolute zero, there can be no waste energy. Entropy is also a measure of the disorder in a system, and although an ideal crystal is by definition perfectly ordered, any positive temperature value means that there is movement within the crystal that causes disorder. For these reasons, there can be no lower entropy physical system, so entropy is always positive.

The science of thermodynamics has evolved over the centuries and its principles apply to almost every device ever invented. Its importance in modern technology can hardly be overestimated.


Contact us: [email protected]

Our Standards, Terms of Use: Standard Terms And Conditions.