Thermodynamic Processes

Introduction

Few could have imagined when the father of thermodynamics “Nicolas Léonard Sadi Carnot”, proposed thermodynamic theorems and cycles; his theories would one day play such a key role in the creation of the vehicle, which has become an integral element of our lives. Later on, Sterling Diesel, Otto, and Ericson expanded on the thermodynamic cycles, resulting in new discoveries and advancements in automobiles. This article will learn about thermodynamic processes. However, before we move on to the processes, we must first grasp the quasi-static process. Hence, when a system is not in thermodynamic equilibrium with its surroundings, it is considered to be in a process at any given time. Thus, a process can be defined as a continuous change in the state of a system that occurs while it is not in thermodynamic equilibrium with its environment.

Definition of Thermodynamics

Thermodynamics is the discipline of physics that deals with the transfer of energy from one form to another and the relationship between heat, temperature, and work done.

The laws of thermodynamics are utilised to convert heat energy from chemical reactions into various usable forms. Energy transformation is based on the fact that energy can only be transformed and used in a variety of industries if it is transformed from one form to another. As we all know, chemical reactions are accompanied by energy. The laws of thermodynamics are concerned with the energy changes that occur during a reaction, not with the rate of the process.

The Role of Thermodynamics

• It helps to determine whether a chemical reaction can occur under certain conditions.
•  It makes it possible to precisely state the efficiency of a specific process.

Thermodynamic System

In thermodynamics, a system is defined as the part of the universe being researched and where measurements are being made. The environment and the system interact with one another, and matter and energies are transferred depending on the type of system. The flow of energy and matter in and out of a system determines its classification.

There Are Three Varieties of Systems:

Open System – It is one in which energy and matter are freely transferred. When water is boiled on a stove without a lid, the container operates as an open system because it receives heat energy from an outside source and the item expelled is water vapour. Both matter and energy can be exchanged between the system and its environment.

Closed System – It is one in which only energy, not matter, can be exchanged with the environment.  On the other hand, it has a constant amount of matter, with the only change being the system’s energy. When we store a shield bottle of water in the fridge, for example, the energy loss to the environment causes the temperature of the water inside the bottle to decrease.

Isolated System- When a system is isolated, it cannot interchange energy or matter with its surroundings. An isolated system is represented by a thermos flask.

Law of Thermodynamics

The universal law of energy conservation that applies to all systems is the first law of thermodynamics. This law states that “the total thermal energy change in every system equals the sum of the internal energy change and the work done.” When a particular quantity of heat, dQ, is applied to a system, some of it is used to increase internal energy, dU, and some is used to perform external work, dW, yielding dQ = dU + dW.

The process or conditions under which heat capacity is transmitted determine the specific heat capacity of gases. There are essentially two types of specific heat capacity for gas. The two types of specific heat capacity are specific heat capacity at constant volume and specific heat capacity at constant pressure. As we all know, chemical reactions are accompanied by energy. The laws of thermodynamics are concerned with the energy changes that occur during a reaction, not with the rate of the process. 

Processes of Thermodynamic

There are six thermodynamics processes: Quasi-static processes, Isothermal Process, Adiabatic process, Isochoric Process, Isobaric Process, and Cyclic Process. Let’s discuss each of them one by one.

Quasi-static processes 

A quasi-statistical thermodynamic process is one which is non-equilibrium, irreversible, and occurs in a finite but large system. This refers to a macroscopic process occurring between two spatially separated parts of a system (i.e., not involving transport of matter or energy), such as heat flowing from a hotter body to a colder body. Quasi-static systems are very common in nature, and exhibit self-organisation and make use of entropy production.

Isothermal Process 

If during a process taking place in a system the temperature remains constant, then the process is “Isothermal”. In this process, all the three Q, W, ΔU may change.Hence, the instance of an ‘ideal gas,’ the internal energy is solely determined by the gas’s temperature. As a result, the amount of heat added (or removed) from the system matches the amount of work done by (or on) the system throughout the isothermal process.  

Adiabatic Process 

An adiabatic process is a thermodynamic cycle that occurs without the exchange of heat between the system and its surroundings. It occurs when the system or surroundings are insulated to prevent heat transfer, such as in a refrigerator. In an adiabatic process with an ideal gas, the relationship between pressure and volume is given by,

PVγ = Constant 

Where γ = Cp/Cv

Cp represents the heat capacity at constant pressure

Cv represents the heat capacity at constant volume

Isochoric Process 

 If a process takes place in a system at a constant volume, the process is called ‘ Isochoric’. Since there is no change in volume, work done W= 0. From the first law of thermodynamics thermodynamics ΔU=Q-W, we have

                                                    Q = ΔU

Thus, in an isochoric process the entire heat given to the system is used in Increasing the internal energy of the system. For example Explosions in gases are Isochoric.

Isobaric Process

An isobaric process is one that occurs at constant pressure.

This equation shows that the work done in the isobaric process is W=P(V2-V1)= n R(T2-T1) when the pressure is kept constant.

Here P = pressure

V1 and V2 are initial and final volume

T1 and T2 are initial and final temperature

R = Ideal gas constant

n  = number of moles

 In this process, the amount of heat provided to the system is divided between growing temperature and doing work, i.e., ΔQ = ΔU + ΔW

For an isobaric process, the equation connecting P, V, and T is V/T=constant, which means that as the temperature rises, so does the volume.

Cyclic Process

In a cyclic process, the system returns to its initial state. There has been no change in internal energy U=0 since the system was returned to its initial state. Total heat absorbed in this process equals total work done by the system, i.e., ΔQ = ΔW

Conclusion:

The following article is meant to provide an overview of the thermodynamic process, from the definition of the terms involved to a description of the energy flows and transformations that take place. You should have a basic understanding of the three laws of thermodynamics, which govern all physical processes in our universe. For example, a light bulb converts electrical energy into light energy. Plants transform sunlight’s radiative energy into chemical energy. Overall, thermodynamics is a vast concept.