**Entropy **is the measure of a system’s thermal energy per unit temperature that is unavailable for doing useful work.

**The laws of Thermodynamics**

Thermodynamics is a branch of physics that highlights the association between temperature, heat, work and energy. Thermodynamics deals with the transfer of energy from one system to another and from one form to another. Four fundamental laws, describe the entire spectrum of thermodynamics namely the Zeroth law of thermodynamics, the First law of thermodynamics, the Second law of thermodynamics and lastly, the third law of thermodynamics. In general, terms, thermodynamics deals with the large-scale response of a system that scientists can measure while conducting experiments. Each law of thermodynamics leads to the establishment of a comprehensive understanding of thermodynamic properties, which help in predicting and comprehending the working principle of a physical system.

**Zeroth law of thermodynamics**

The extension of the principle, which is known as thermal equilibrium, has provided a comprehensive description of the Zeroth law of thermodynamics. This states that two systems are in thermal equilibrium, with the third system being in contact with each other. For instance, we have to consider the temperature of three systems, T_{1, }T_{2, }and T_{3,} in such a way where T_{1}= T_{3 } along with T_{2}=T_{3. } Hence, the temperature two system T_{1}=T_{2… }Suppose the temperature of T_{3 }of a thermometer is equal to the temperature of T_{1 }if the thermometer and system are in thermal equilibrium.

It is worth highlighting that when two systems are in a thermal equilibrium state, they have the same temperature. When two systems reach a thermal equilibrium state, heat, which is a form of energy, is transferred between them, which is described as Zeroth’s law of thermodynamics.

**The First law of thermodynamics**

The First law of thermodynamics developed from the experimental demonstration that mechanical work and heat work are interchangeable forms of energy. The first law of thermodynamics strengthens the conservation of energy principle to systems where heat transfer and work done are the methods of energy transfer into or out of the system. It is also stated that energy cannot be created nor destroyed; it can only be transformed from one form to another.

Deep down into this law of thermodynamics, it has been identified that change in the internal energy of an object is equal to the net work done by the object, which is defined by the question ▲U= Q-W. In this equation, ▲U represent the alteration in internal energy U of the system, Q is the net heat transfer to the specific system, and W is the sum of the total work done on or by the system.

The internal energy U is a state function, and it does not depend upon the path by which the state has reached. On the other hand, the Q and W may depend upon paths, which signify the difference as Q-W always produces the same value of ▲U= U2- U1. The first law of thermodynamics has been validated experimentally many times in different places. It enables the conversion of energy from one form to another form; however, it never allows energy to be produced or destroyed in the conversion process.

The first law of thermodynamics also suggests that heat, which is a form of energy to be transferred from a cold system to a hot system up until the amount of transfer heat transferred lessens the internal energy of the hot system. Nevertheless, this phenomenon never happens as heat can only be transferred from a hot body to a cold body. For this reason, the second law of thermodynamics has shed light on the above-mentioned aspect, which illustrates that heat cannot be spontaneously transferred from a cold body to a hot body.

**Second law of thermodynamics**

The Second law of thermodynamics implies that the state of entropy of the entire universe as an isolated system will increase spontaneously. The term entropy is the amount of disorder in a system, which also highlights uncertainty and randomness. In the early 1850s, the concept of entropy was introduced by Clausius as a detailed mathematical way of testing whether this specific process violated the Second law of thermodynamics. The experiment commences with the definition that if a quantity of heat Q is transferred into a heat reservoir at constant temperature T therefore, its entropy upsurges by ▲S=Q/T.

The change in entropy provides a thermodynamic definition of temperature. In this context, it can be assumed that if the amount of heat Q flows from two reservoirs, R_{1 }and R_{2, }that are at temperatures T_{1 }T_{2,} then net change in entropy in the system is described by the equation ▲S= Q/T_{2- }Q/ T_{1.}

_{ }The above-highlighted information highlights that ▲S is positive, which means T_{1> }T_{2. }Hence, the result suggests that heat never flows spontaneously from colder bodies to hotter bodies is comparable to requiring the net changes in entropy to be positive for a spontaneous heat transfer. Besides that ▲, S is zero if the temperature of the two systems is equal and the resolver is in equilibrium.

Entropy is a measure of a system’s thermal energy per unit temperature and work acquired from ordered molecular motion; therefore, the amount of entropy is also a measurement of the randomness or molecular disorder of a system. As a result, entropy, which signifies the disorderliness of the universe, is identified to have increased since the inception of our universe.

**The Third law of thermodynamics **

According to the Third law of thermodynamics, a perfect crystal at zero Kelvin temperature**,** which is also known as absolute zero, has zero entropy. This law of thermodynamics also highlights that the entropy of a closed system in thermodynamic equilibrium leads to a constant value when its temperature is near absolute zero. This constant value does not depend upon different parameters that characterize the system, like applied magnetic field or pressure.

At zero kelvin, the system should be in a state with the minimum required energy. The third law of thermodynamics is not intuitive; however, it is often derived empirically since the entropy of a system always approaches the similar minimum value of absolute temperature and comes close to zero.

**Gibbs free energy**

The Gibbs free energy, which is signified as G, refers to thermodynamic potential that is used to calculate the maximum amount of work rather than pressure-volume work, and it can be performed by a thermodynamically closed system at constant pressure and temperature. The Gibbs free energy change is defined by the equation ▲G=▲H-T▲S, referring to the maximum amount of non-volume expansion work that may be extracted from a thermodynamically closed system. If the reactants are all in their thermodynamic standard states, then the expression of Gibbs energy is ▲G^{0}=▲H^{0}-T▲S^{0 }where T is absolute temperature, H is enthalpy, and S is entropy.

**What makes our universe disorder? **

Thermodynamics is significant to different scientific explorations, from engineering to natural science to chemistry to physics, which is governed by the law of conservation of energy. The notion of thermodynamics of an isolated system has indicated the notion of an isolated system that does not let energy in or out of it, and the second law of thermodynamics provides an idea regarding entropy, which creates molecule disorder, which also elevates the internal energy of a system.

Since the measure of entropy is based on probabilities, the likelihood of entropy decreases in a system on an instance; however, from a statistical point of view, it is found to be relatively uncommon. The Big Bang theory provides an understanding of singularity, an infinitely condensed stage of the universe that explodes and continues expanding; hence, entropy is constantly increasing.

## FAQ

**What is the Second law of thermodynamics?**

The Second law of thermodynamics implies that the state of entropy of the entire universe as an isolated system will increase spontaneously. The term entropy is the amount of disorder in a system, which also highlights uncertainty and randomness. In the early 1850s, the concept of entropy was introduced by **Clausius** as a detailed mathematical way of testing whether the Second law of thermodynamics was violated by this specific process.

**What is entropy?**

Entropy is a measure of a system’s thermal energy per unit temperature and work acquired from ordered molecular motion; therefore, the amount of entropy is also a measurement of the randomness or molecular disorder of a system. As a result, entropy, which signifies the disorderliness of the universe, is identified to have increased since the inception of our universe.

**How does entropy bring disorder to the Universe?**

Since the measure of entropy is based on probabilities, the likelihood of entropy decreases in a system on an instance; however, from a statistical point of view, it is found to be relatively uncommon. The Big Bang theory provides an understanding of singularity, an infinitely condensed stage of the universe that explodes and continues expanding; hence, entropy is constantly increasing.