How to understand enthalpy and entropy?

Hehe, I don’t quite understand either, but entropy is irreversible

Is this a production technique? :lol

Entropy: 1: In physics, it refers to the quotient of thermal energy divided by temperature, and it indicates the degree to which heat is converted into work. 2: A function in science and technology used to describe and characterize the disorder of a system. It is also used in social sciences as a metaphor for certain states of human society.

Entropy in thermodynamics is one of the parameters that characterize the state of a substance, usually denoted by the symbol S. In classical thermodynamics, it can be defined using an increment as dS = (dQ/T), where T is the thermodynamic temperature of the substance ； dQ is the heat added to the substance during the entropy increase process. The subscript “reversible” indicates that the change process induced by the heating process is reversible. If the process is irreversible, then dS > (dQ/T), which indicates irreversibility. On a microscopic level, entropy is a measure of the disorder of the numerous microscopic particles that make up a system; the more disordered and chaotic the system, the greater its entropy. The microscopic essence and statistical meaning of the irreversibility of thermodynamic processes is that the system moves from order to disorder, from states with lower probabilities to states with higher probabilities. 　　The entropy per unit mass of a substance is called specific entropy, denoted as s. Entropy was initially introduced as a parameter of the state of matter that reflects the irreversibility of spontaneous processes, based on the second law of thermodynamics. 　　The second law of thermodynamics is a principle derived from numerous observations, and it can be expressed as follows: ① Heat always flows from hotter objects to colder objects; it is impossible for heat to flow in the opposite direction without causing some other change ； 　　②Work can be completely converted into heat, but no heat engine can convert all the heat it receives into work in a complete and continuous manner (in other words, a second kind of perpetual motion machine cannot be created) ； 　　③In an isolated system, the processes that actually occur always result in an increase in the entropy of the entire system; this is the principle of entropy increase. Friction causes a portion of mechanical energy to be irreversibly converted into heat, increasing entropy. The heat dQ is transferred from the object at higher temperature (T1) to the object at lower temperature (T2). The entropy of the object at higher temperature decreases by dS1 = dQ/T1, while the entropy of the object at lower temperature increases by dS2 = dQ/T2. When these two objects are considered as a single system, the change in entropy is dS = dS2 + dS1 > 0; that is, entropy increases. 　　The physicist Boltzmann defined entropy as the probability of a particular state: the number of ways atoms can be arranged. It can be precisely expressed as: S=KlogW

The physical meaning of enthalpy can be understood as, under the special conditions of constant pressure and only volume work being done, Q=ΔH, that is, the change in heat during a reaction. Because only under these conditions does enthalpy exhibit its properties. For example, when a substance is heated at constant pressure, it absorbs heat and its temperature rises; ΔH>0, so the enthalpy of the substance at high temperatures is greater than its enthalpy at low temperatures. Similarly, for an exothermic chemical reaction at constant pressure, ΔH

The physical meaning of enthalpy can be understood as, under the special conditions of constant pressure and only volume work being done, Q=ΔH, that is, the change in heat during a reaction. Because only under these conditions does enthalpy exhibit its properties. For example, when a substance is heated at constant pressure, it absorbs heat and its temperature rises; ΔH>0, so the enthalpy of the substance at high temperatures is greater than its enthalpy at low temperatures. Similarly, for an exothermic chemical reaction at constant pressure, ΔH

Don’t take things out of context; the moderator had better take a look at physical chemistry

Enthalpy is an energy parameter in a thermodynamic system. It is specified to be denoted by the letter H (unit: joule, J), with H coming from the English word Heat Capacity. The physical meaning of enthalpy can be understood as, under the special conditions of constant pressure and only volume work being done, Q=ΔH, that is, the change in heat during a reaction. Because only under these conditions does enthalpy exhibit its properties. For example, when a substance is heated at constant pressure, it absorbs heat and its temperature rises; ΔH>0, so the enthalpy of the substance at high temperatures is greater than its enthalpy at low temperatures. Similarly, for an exothermic chemical reaction at constant pressure, ΔH

Entropy refers to the degree of disorder in a system. It has important applications in fields such as cybernetics, probability theory, number theory, astrophysics, and life sciences, and more specific definitions have been developed within different disciplines; it is a very important parameter in various fields. Entropy was introduced by Rudolf Clausius and is applied in thermodynamics. Later, Claude Elwood Shannon was the first to introduce the concept of entropy into information theory. 1. In physics, it refers to the quotient of thermal energy divided by temperature, indicating the degree to which heat is converted into work. 2. A function in science and technology used to describe and characterize the disorder of a system. It is also used in social sciences as a metaphor for certain states of human society. 3. Applications in thermodynamics: Entropy is one of the parameters used in thermodynamics to describe the state of a substance, and it is usually denoted by the symbol S. In classical thermodynamics, it can be defined using an increment as dS = (dQ/T), where T is the thermodynamic temperature of the substance ； dQ is the heat added to the substance during the entropy increase process. The subscript “reversible” indicates that the change process induced by the heating process is reversible. If the process is irreversible, then dS > (dQ/T), which indicates irreversibility. On a microscopic level, entropy is a measure of the disorder of the numerous microscopic particles that make up a system; the more disordered and chaotic the system, the greater its entropy. The microscopic essence and statistical meaning of the irreversibility of thermodynamic processes is that the system moves from order to disorder, from states with lower probabilities to states with higher probabilities. 　　The entropy per unit mass of a substance is called specific entropy, denoted as s. Entropy was initially introduced as a parameter of the state of matter that reflects the irreversibility of spontaneous processes, based on the second law of thermodynamics. 　　The second law of thermodynamics is a principle derived from numerous observations, and it can be expressed as follows: ① Heat always flows from hotter objects to colder objects; it is impossible for heat to flow in the opposite direction without causing some other change ； 　　②Work can be completely converted into heat, but no heat engine can convert all the heat it receives into work in a complete and continuous manner (in other words, a second kind of perpetual motion machine cannot be created) ； 　　③In an isolated system, the processes that actually occur always result in an increase in the entropy of the entire system; this is the principle of entropy increase. Friction causes a portion of mechanical energy to be irreversibly converted into heat, increasing entropy. The heat dQ is transferred from the object at higher temperature (T1) to the object at lower temperature (T2). The entropy of the object at higher temperature decreases by dS1 = dQ/T1, while the entropy of the object at lower temperature increases by dS2 = dQ/T2. When these two objects are considered as a single system, the change in entropy is dS = dS2 + dS1 > 0; that is, entropy increases.