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Entropy is a key term in physics and chemistry, and it can also be applied to other fields such as cosmology and economics. It is an aspect of thermodynamics in physics. It is a fundamental idea in physical chemistry. More crucially, entropy may be defined in a multitude of ways, making it applicable to a wide range of fields such as thermodynamics, cosmology, and even economics. Entropy is a term that describes both the spontaneous changes that occur in everyday phenomena and the universe’s tendency toward chaos.
Entropy Definition
The measure of a system’s dysfunction is entropy. It is a thermodynamic system’s extensive property, meaning its value varies depending on the amount of matter present. Entropy is commonly represented by the letter S in equations and is measured in joules per kelvin (J⋅K−1) or kg⋅m2⋅s−2⋅K−1. The entropy of a well ordered system is low.
Entropy Example
As a block of ice melts, its entropy increases. It’s clear to see how the system’s disarray is increasing. Ice is made up of water molecules that are linked together in a crystal lattice. As ice melts, molecules gain energy, spread out more, and lose structure, resulting in a liquid. Similarly, changing from a liquid to a gas, such as water to steam, increases the system’s energy.
On the other hand, energy can be depleted. This occurs when steam condenses into water or water condenses into ice. Because the stuff is not in a closed system, the second law of thermodynamics is not broken. While the entropy of the system under study may be decreasing, the environment’s entropy is increasing.
The Second Law of Thermodynamics
Every isolated system’s entropy grows over time, according to the second law of thermodynamics. Isolated systems approach thermal equilibrium, which is the state of maximum entropy for the system. To put it another way, the cosmos’ entropy (the ultimate isolated system) is constantly increasing and never diminishing.
The second rule of thermodynamics states that if a room is not cleaned and tidied, it will inevitably get more messy and chaotic over time, no matter how careful one is to keep it clean. When a room is cleaned, the entropy in the room decreases, but the work to clean it results in an increase in entropy outside the room that is more than the entropy lost.
Entropy and the Second Law of Thermodynamics
The total entropy of a closed system cannot decrease, according to the second law of thermodynamics. Within a system, however, one system’s entropy can be reduced by increasing the entropy of another.
Exothermic, Energy
In thermochemistry, an exothermic reaction is defined as one in which the total standard enthalpy change ΔH⚬ is negative. Heat is produced in exothermic reactions, which entail the replacement of weak bonds with stronger bonds. The phrase is frequently confused with exergonic reaction, which is defined by the International Union of Pure and Applied Chemistry as “… a reaction for which the overall standard Gibbs energy change ΔG⚬ is negative.” Because ΔH⚬ contributes significantly to ΔG⚬ a substantially exothermic process is frequently also exergonic. Exothermic and exergonic chemical reactions account for the majority of the remarkable chemical reactions seen in classrooms. An endothermic reaction, on the other hand, is one that absorbs heat and is fueled by an increase in the system’s entropy.
Examples
Combustion, the thermite reaction, mixing strong acids and bases, and polymerizations are only a few examples. In everyday life, hand warmers, for example, use the oxidation of iron to produce an exothermic reaction:
4Fe + 3O2 → 2Fe2O3 ΔH⚬ = – 1648 kJ/mol
Exothermic reactions involving the combustion of hydrocarbon fuels, such as natural gas, are particularly important:
2CH4 + 2O2 → CO2 + 2H2 O ΔH⚬ = – 890 kJ/mol
The majority of the energy released in these samples was stored in O2, which has a rather weak double bond.
In most chemical reactions, existing chemical connections are broken as well as new, stronger chemical bonds are formed. When atoms come together to form new, more stable chemical bonds, the electrostatic forces that bring them together leave a substantial surplus of energy in the bond (usually in the form of vibrations and rotations). The new bond will swiftly break apart if that energy is not discharged. Instead, the new bond can lose its surplus energy by radiation, transfer to other molecular motions, or collisions with other molecules, and then become a stable new bond. The heat that escapes the chemical system is this extra energy.
Exothermic processes that result in fires and explosions are wasteful because capturing the released energy is challenging. In aerobic respiration, nature performs combustion reactions under highly controlled settings, avoiding fires and explosions, in order to catch the released energy, for example to generate ATP.
Potential Energy
The energy released as a result of a change in position, composition, or arrangement is known as potential energy. It is also the energy associated with object attraction and repulsion forces. Because any object that is lifted from its resting position has stored energy, it is referred to as potential energy because it has the ability to perform work once released.
When a demolition machine’s heavy ball is held at an elevated position, for example, it stores energy. Potential energy is the name given to this stored positional energy. A drawn bow, likewise, can store energy as a result of its position.
Conclusion:-
Because work is generated by ordered molecular motion, entropy is a measure of a system’s molecular disorder or unpredictability. The concept of entropy sheds light on the direction of spontaneous change in a variety of contexts.
