Carnot cycle

An ideal closed thermodynamic cycle with reversibility is known as a Carnot cycle. Isothermal expansion, adiabatic expansion, isothermal compression, and adiabatic compression are the four sequential processes that take place. The substance can be expanded and compressed throughout these operations up to the desired point and returned to its initial state. https://cdn1.byjus.com/wp-content/uploads/2023/03/The-Carnot-Cycle-updated.png Following are the four processes of the Carnot cycle: In (a), the process is reversible isothermal gas expansion. In this process, the amount of heat absorbed by the ideal gas is qin from the heat source at a temperature of Th. The gas expands and does work on the surroundings. In (b), the process is reversible adiabatic gas expansion. Here, the system is thermally insulated, and the gas continues to expand and work is done on the surroundings. Now the temperature is lower, Tl. In (c), the process is a reversible isothermal gas compression process. Here, the heat loss qout occurs when the surroundings do the work at temperature Tl. In (d), the process is reversible adiabatic gas compression. Again the system is thermally insulated. The temperature again rises back to Th as the surrounding continue to do their work on the gas.

Thermodynamics temperature

 The study of energy and its changes is the focus of the field of physics known as thermodynamics. The concept of temperature is crucial to understanding thermodynamics because it represents the average kinetic energy of the particles in a system.

The Kelvin (K) scale, which is based on the absolute zero point, the temperature at which all molecular motion ends, is used to measure temperature in thermodynamics. The triple point of water, a state when the three phases of water coexist in equilibrium, has a temperature of 273.15 Kelvins, which is linked to the Celsius (°C) scale by the equation K = °C + 273.15.

Temperature is a crucial parameter in thermodynamics that influences a system's behavior. For instance, the ideal gas law states that PV = nRT, where P is pressure, V is volume, n is the number of moles of gas, R is the gas constant, and T is the absolute temperature, relates the pressure, volume, and temperature of a gas. 

The direction and extent of heat transmission between two systems, as well as the effectiveness of thermodynamic cycles like heat engines and refrigeration cycles, are all significantly influenced by temperature.

Thermodynamic Potential

                                   

Hello friends✋, in todays reflection i would be letting you all move through thermodynamic potential and the types involved. Please spare some precious time reading this blog as what we know is a drop but what we don't know is an ocean so make your drop be a part of the ocean. 

 

 Thermodynamic Potential 

Thermodynamic potential or fundamental function is a quantity used to represent the state of a system or is the energy functions formed be the combining the basic thermodynamic variables.

The types of Thermodynamic Potential 

1. Internal Energy
2. Enthalpy
3. Helmholtz energy function
4. Gibbs free energy

• Internal Energy

The energy possessed by the system due to molecular constitution is called internal energy. When a system passes from one state to another state, the internal energy depends on initial and final state and doesn't depend on path followed which is known as state function.

The internal energy of a system is denoted by the symbol "U" and is typically expressed in units of energy (such as joules or calories). It is an extensive property, meaning it depends on the amount or quantity of substance present in the system.

The internal energy of a system can change due to various factors, such as heat transfer (thermal energy exchange) and work done on or by the system. When heat is added to a system or work is done on it, the internal energy increases. Conversely, when heat is lost from the system or work is done by the system, the internal energy decreases.

The change in internal energy (ΔU) of a system is given by the equation:

ΔU = Q - W

where:

ΔU is the change in internal energy

Q is the heat added to the system

W is the work done on the system

Internal energy is a state function, which means it depends only on the current state of the system and not on the path taken to reach that state. It can be related to other thermodynamic properties, such as temperature, pressure, and volume, through various equations and laws, such as the First Law of Thermodynamics.

Overall, the internal energy of a system is a crucial quantity in thermodynamics, as it represents the total energy content and plays a significant role in understanding and analyzing energy transfers and transformations in physical and chemical processes.

Figure 1:Molecules experiencing internal energy

• Enthalpy

The total energy of thermodynamically system is called enthalpy. It is a heat function at constant pressure.

It is denoted by the symbol "H" and is a function of the internal energy, pressure, and volume of the system. Enthalpy is particularly useful in the study of chemical reactions and phase changes.

The enthalpy of a system can be thought of as the amount of heat absorbed or released by the system during a process at constant pressure. When a chemical reaction occurs at constant pressure, the change in enthalpy (ΔH) is equal to the heat exchanged between the system and its surroundings.

Enthalpy is defined as:

H = U + PV

where:

H is the enthalpy of the system

U is the internal energy of the system

P is the pressure of the system

V is the volume of the system

Enthalpy is an extensive property, meaning it depends on the quantity of the substance or the size of the system. The standard enthalpy change of a reaction (ΔH°) refers to the enthalpy change when all reactants and products are in their standard states at a specified temperature and pressure.

Enthalpy is often used in various fields of science and engineering, such as chemistry, physics, and thermodynamics, to analyze and predict the energy changes associated with processes and reactions.

            Figure 2: Enthalpy

• Helmholtz Function

The energy function of thermodynamic system, which changes due to external work applied on the isothermal process.

 It is denoted by the symbol "F" or "A" and is named after the German physicist Hermann von Helmholtz.

The Helmholtz function is defined as:

F = U - TS

where:

F is the Helmholtz function

U is the internal energy of the system

T is the absolute temperature of the system

S is the entropy of the system

The Helmholtz function combines information about both the internal energy and entropy of a system. It represents the maximum amount of work that can be extracted from a system at constant temperature and volume. In other words, it is a measure of the system's capacity to do useful work.

The Helmholtz function is particularly useful in systems at constant temperature and volume, such as closed systems or systems undergoing reversible processes. The change in Helmholtz function (ΔF) for a process occurring at constant temperature and volume is equal to the maximum useful work that can be obtained from the system during the process.

The Helmholtz function is related to other thermodynamic potentials, such as the internal energy (U), enthalpy (H), and Gibbs free energy (G). These potentials are related through various thermodynamic equations and can be used to analyze and predict the behavior of a system under different conditions.

                

• Gibbs free energy

It is a energy function of thermodynamic system which remains constant under the process of isothermal and isobaric.

It is named after the American physicist Josiah Willard Gibbs.

The Gibbs free energy is defined as:

G = H - TS

where:

G is the Gibbs free energy

H is the enthalpy of the system

T is the absolute temperature of the system

S is the entropy of the system

The Gibbs free energy combines information about the enthalpy and entropy of a system. It represents the maximum amount of useful work that can be extracted from a system at constant temperature and pressure.

For a chemical reaction occurring at constant temperature and pressure, the change in Gibbs free energy (ΔG) is related to the spontaneity of the reaction. If ΔG is negative, the reaction is spontaneous in the forward direction and releases free energy. If ΔG is positive, the reaction is non-spontaneous in the forward direction and requires an input of free energy. If ΔG is zero, the reaction is at equilibrium.

The Gibbs free energy is particularly useful in determining the equilibrium conditions of a system and predicting the direction in which a reaction will proceed. It allows us to assess the balance between enthalpy and entropy contributions and determine whether a process is thermodynamically favorable.

The Gibbs free energy is related to other thermodynamic potentials, such as the internal energy (U), enthalpy (H), and Helmholtz function (F). These potentials are connected through various thermodynamic equations and provide valuable insights into the behavior of a system under different conditions.

      

              Figure 4: Significance of Gibbs free energy

Thank you guys, really appreciated you came along reading and acquiring knowledge on this topic. Lastly, with great honors i would like to thank Mr. Shacha Thinley for implementing new techniques though the content remains the same, indeed it was something great.