CBSE Class 11 Physics Revision Notes Chapter 12

Class 11 Physics Revision Notes for Chapter 12 – Thermodynamics

Revising concepts of thermodynamics can be tricky because of its extensive content. Extramarks provides Revision Notes which contain short, easy-to-understand pointers and explanations. These are helpful for students to memorise and retain information during important examinations.

Thermodynamics Class 11 Physics Notes

A thermodynamic system is made up of a large number of molecules of matter (solid, liquid or gas) that are structured in such a way that they have specific pressure, volume and temperature values, which are called the thermodynamic state variables.

In thermodynamics, we analyse thermodynamic systems as a whole and learn about the interaction of heat and energy as the thermodynamic state changes.

Extramarks Class 11 Physics Revision Notes for the topic of Thermodynamics have been developed in ways that are consistent with the CBSE syllabus. It includes all the major theories as well as their explanations. It is one of the important chapters for Class 11 examinations as well. 

Therefore, it is crucial that students fully comprehend the fundamental concepts. They can benefit from Extramarks Revision Notes to help them understand the chapter, Thermodynamics.

Class 11 Physics Chapter 12 Notes

The thermodynamic laws are significant physical quantities. They are comparable to energy and temperature. Entropy is also a physical quantity used to characterise thermodynamic systems in thermal equilibrium.

There Are Four Laws of Thermodynamics. They are given below:

Zeroth Law of Thermodynamics

According to the Zeroth Law of Thermodynamics, when thermodynamic systems A and B are individually in thermal equilibrium with a third thermodynamic system, C, systems A and B are likewise in thermal equilibrium with each other.

First Law of Thermodynamics

If 

ΔQ=Heat supplied to the system by the surroundings 

ΔW=Work done by the system on the surroundings 

ΔU=Change in internal energy of the system.

According to the First Law of Thermodynamics, energy can neither be created nor destroyed. Energy simply changes from one form to another. The law states that the total amount of heat supplied to the system by its environment equals the product of the work done by the system on its environment and the change in internal energy of the system.

Hence,

ΔQ=ΔU+ΔW.

Second Law Of Thermodynamics

The Second Law of Thermodynamics tells us that no system can exist in which the amount of heat being converted into work is the amount of heat absorbed from the reservoir. 

This law can be expressed in a variety of ways.

Even if the contents of all the statements are the same, the following two are the most important.

  • Kevin Plank Statement: No technique can fully convert heat from a reservoir into work without also absorbing some of the heat from the reservoir. 
  • Clausius Statement: There is no process that can provide heat transfer simply from a colder object to a hotter one. 

It is impossible to achieve 100 per cent efficiency in heat engines or infinite CoP in freezers.

Third Law Of Thermodynamics

At absolute zero temperature, the system holds the least energy, according to the Third Law of Thermodynamics.

Notes Of Chapter Thermodynamics Class 11 Physics

Sub-topics of Class 11 Physics Chapter 12 Thermodynamics include:

  • Introduction to thermodynamics
  • Thermal equilibrium
  • Heat, internal energy and work
  • Zeroth law of Thermodynamics
  • Specific heat capacity
  • The first law of thermodynamics
  • The equation of state and Thermodynamic state variables 
  • Heat engines
  • Refrigerators and heat pumps
  • Thermodynamic processes
  • The second law of thermodynamics
  • Carnot Engine
  • Reversible and irreversible processes

CBSE Class 11 Physics Notes Chapter 12 Thermodynamics

What Do You Mean by Enthalpy?

Enthalpy, in thermodynamics, is the unit of energy measurement. Enthalpy is measured as the sum of all the heat in a system. The product of volume and pressure and the internal energy of the system is called enthalpy. 

Mathematically, H = E + PV

H = Enthalpy

E = Internal energy

P = Pressure of the system

V = Volume of the system

Download CBSE Class 11 Physics Notes Thermodynamics 

Extramarks Class 11 Physics Chapter 12 Thermodynamics notes are easy for students to access and convenient to read regardless of the time and place. There are accurate and reliable Extramarks consult subject matter experts to provide these notes. Moreover, these notes adhere to the updated CBSE syllabus.  

FAQs (Frequently Asked Questions)

The study of energy, energy transformation and the link between energy and matter is known as thermodynamics. Simply put, it claims that energy can change forms throughout an interaction but that the total amount of energy remains constant. Physical and chemical thermodynamics are interlinked. Students will learn about energy as well as the conversion of energy between different forms and the ability of energy to conduct work.

The point at which a system’s thermal energy is no longer usable is known as entropy. The amount of entropy in a system quantifies the molecular disorder (or randomness) of a system since work is produced by organised molecular motion. Entropy is represented by a wildfire. In comparison to solid fuel combustion, solid wood burning produces ash, smoke, and fumes that transfer energy more quickly. Entropy can be observed in a variety of ways in our daily lives and surroundings.

 

Bodies will be in thermal equilibrium with each other if two thermodynamic systems are in thermal equilibrium with a third. The transitive link will lead to the creation of thermal equilibrium between systems. When two cups of water are filled with hot and cold water, this phenomenon can be seen. After a few hours, we can leave them on the table to reach thermal equilibrium with the ambient temperature.

Open, closed, and isolated systems are the three different types of systems. They are explained as follows:

  • Open system: Capable of exchanging matter and energy with its surroundings. 
  • Closed system: It is limited to exchanging energy with its immediate environment. 
  • Isolated system: There is no environmental interaction. 

An isentropic condition is a situation in thermodynamics when the entropy at a certain location is constant. Reversible and adiabatic processes operate in isentropic environments.

Heat will circulate as long as both bodies are heated. Thermal equilibrium occurs when two bodies achieve the same temperature and there is no heat exchange between them. Temperature equilibrium happens when two items in physical contact do not exchange heat energy with one another. At the same temperature, two substances are said to be in thermal equilibrium. This is the most fundamental definition of thermal equilibrium.

Internal energy is the energy that any system possesses as a result of its molecular kinetic energy and molecular potential energy. Both of these energies are analysed concerning the frame of the centre of mass.

Internal energy is fully reliant on the state, making it a state variable. Internal energy is only present in real gases due to their molecular motion, but it is mathematically given in ideal gases by 

U=nfRT/2.

where,

n is the number of moles

f is the degree of freedom

R is the universal gas constant

T is the temperature in kelvin

Internal Energy can be changed by either giving heat energy or performing work.

Heat energy is the energy that is transferred to or from a system due to temperature differences via conduction, convection or radiation.

Work is defined as the energy transferred from one system to another by force moving its point of application in its direction.

Work done by the system is given by

W=∫Fdx=∫PsAdx=∫PdV

Ps is the pressure of the system on the piston.

The work done by the system is positive when the system is expanding and negative when the system is collapsing.

Internal energy is a state function, whereas work and heat are path functions.

Even though they may appear similar, heat and work are two distinct terminologies.

A thermodynamic process occurs when a few changes occur in the state of a thermodynamic system, i.e., the system’s thermodynamic parameters vary over time. Isothermal, adiabatic, isobaric and isochoric thermodynamic processes are included in thermodynamic processes which are explained below:

  • Isothermal Process:

It is a thermodynamic process that maintains a constant temperature.

Conditions-

The container’s walls should be fully conductive to allow for the unimpeded flow of heat between the gas and its surroundings.

To allow time for heat exchange, the compression or expansion process must be slow.

Both of these conditions are regarded as optimal.

  • Adiabatic Process:

It is a thermodynamic process in which no heat exchange occurs with the surroundings.

Conditions-

The container’s walls must be completely non-conducting in order to avoid any heat exchange between the gas and its surroundings.

The compression or expansion process must be quick enough that there is no time for heat exchange.

These are ideal conditions that are difficult to realise.

  • Isochoric Process:

It is a thermodynamic process in which the volume does not change.

Condition-

A gas that is being heated or cooled inside a rigid container.

  • Isobaric Process:

It is a thermodynamic process that maintains constant pressure.

Condition-

When the piston is in a container, it can move freely and is not connected by any agent.

A quasi-static process is a thermodynamic process that is infinitely slow.

  • When a process is quasi-static, the system changes gradually at an extremely slow speed, maintaining mechanical and thermal balance with its environment at every instant.
  • The quasi-static process is ideal. Unless otherwise specified, we regard all processes to be quasi-static.

Sadi Carnot invented the Carnot cycle, which is an ideal cycle of operation for a heat engine.

The Carnot heat engine is the engine used to realise this ideal cycle.

Given below is the construction of a Carnot Engine-

  • Source of Heat: The source of heat is kept at a constant higher temperature T1, from which the working substance absorbs heat. The source is said to have a limitless thermal capacity, and therefore any amount of heat can be extracted from it without changing its temperature.
  • Sink of Heat: The sink is kept at a constant lower temperature T2, to which the working substance can emit any amount of heat. It also has an infinite thermal capacity, and therefore its temperature remains constant at T2 no matter how much heat is applied to it.
  • Working substance: A perfect gas serves as the working substance. It is placed in a cylinder with non-conducting sides and a fully conducting base. This cylinder is held together by a completely non-conducting and frictionless piston.
  • Aside from these necessary components, there is a properly insulating stand or pad on which the cylinder can be placed. It completely isolates the working substance from its surroundings, allowing the gas to undergo adiabatic changes.