An Explanatory Note on Entropy

Introduction :

Entropy (S) is the amount of thermal energy in a system per unit temperature that can’t be utilised to do worthy work. Entropy is a measure of a system’s molecular disorder, or unpredictability, because by orderly molecular motion the work is generated.

Unit :

Entropy per unit mass (SI unit: J⋅K−1⋅kg−1) or entropy per unit amount of substance (SI unit: J⋅K−1⋅mol−1) is the most common and easy way to express a substance’s entropy.

The idea of entropy provides a remarkable insight into the direction of spontaneous change in day to day situations. It was invented in 1850 by a German scientist named Rudolf Clausius, and it quickly became a hallmark of 19th-century physics.

Entropy is a mathematical concept that expresses the intuitive sense of which operations are impossible, even though they do not contradict the fundamental law of energy conservation.If a block of ice is placed on a hot stove, for example, will undoubtedly melt as the stove cools. Because no small modification will cause the melted water to revert back into ice while the stove heats up, this process is called irreversible. In contrast, depending on whether a tiny amount of heat is given to or taken from the system, a block of ice placed in an ice-water bath will either melt or freeze a bit more. Because just a minuscule amount of heat is required to reverse the process from progressive freezing to progressive thawing, it is reversible. Similarly, compressed gas confined in a cylinder could either expand freely into the atmosphere (an irreversible process) if a valve was opened, or it could accomplish beneficial work by pushing a moveable piston against the force required to confine the gas. Because a minor increase in the restraining force can switch the direction of the process from expansion to compression, the latter process is reversible. 

For reversible processes, the system is in equilibrium with its environment, but not for irreversible processes.

Entropy properties:

Entropy can be dispersed over a surface, accumulated inversely, or directly accumulated. It’s also possible to extract, decompress, or move it to another object. We can identify it with our own energies this way.

We know that entropy has a substantial impact on the state of an object. When there is a scarcity of a material, it is viewed as frigid. If the material story contains an increasing degree of entropy, it can be considered even hotter. As a result, we know it plays a critical part in all thermal characteristics and can be regarded as the source of these effects. There is no temperature or heat without this measurement. It usually spreads over a homogenous mass and is eliminated automatically, more or less swiftly and uniformly throughout the volume.

The heating coil of a power plant generates a huge quantity of entropy. They can also be found in an oil burner’s flame and on the disc brake system’s friction surfaces. Another location where a lot of it is produced is in the muscles of an athlete who is always moving. In the brain, the same is true. When we think, we generate a huge quantity of entropy.

Formula for Entropy:

1. If the operation is taking place at a constant temperature, the entropy will also be constant.

ΔS system =qrevT ,where

ΔS = it is the change in entropy

qrevT= it is the reverse of heat

T = it is the temperature in Kelvin

2. Moreover, if the reaction of the process is known then we can find ∆Srxn by using a table of standard entropy values.

∆Srxn = Σ∆Sproducts–Σ∆Sreactants

∆Srxn  – refers to the standard entropy values

Σ∆Sproducts = refers to the sum of the ∆Sproducts

Σ∆Sreactants– refers to the sum of the ∆Sreactants

3. Is the Gibbs free energy (ΔG) and the enthalpy (ΔH) can also be used to find ΔS

ΔG = ΔH – TΔS

Entropy as per the Second Law of Thermodynamics:

 According to the second law of thermodynamics, every process involves a cycle, and the system’s entropy will either remain constant or grow. Furthermore, even if the cyclic process is changing, the entropy will remain constant. Furthermore, when a process is immutable, the entropy increases.

Watching a movie, for example, is a changing process since you can view it backwards. In contrast to blowing up a structure, frying an egg is an irreversible change. The melting of metals is another example of a changing phase. Furthermore, several microscopy processes can be reversed.

Conclusion :

The entropy of a system is a measure of how much of it can’t be used to produce work. Entropy is valuable because it gives information about structural changes that occur as a result of a given process. In some ways, entropy is beneficial for determining the efficiency of something’s internal energy.

The amount of thermal energy or heat per temperature is measured by entropy. In your kitchen, entropy can be seen in the form of a campfire, ice melting, salt or sugar dissolving, popcorn forming, and boiling water.