Thermodynamics: Introduction

11th Chemistry NCERT notes

It is the study of the flow of energy. It encompasses the study of the flow of heat as well as mass.

Thermodynamics terminology

System: The part of the universe observation is called system.

Surrounding: The part of the Universe not under observation is called Surrounding.

System and surrounding

System + Surrounding = Universe

Types of System

  • Open System: A system in which both flow of mass and heat is possible.

Open system

  • Closed System: A system in which flow of heat is possible but flow of mass is not possible.

closed system

  • Isolated System: A system in which neither heat nor mass can flow in or out.

Isolated system

The State of the System

State of System: When microscopic properties have definite value, the conditions of existence of the system is known as the state of the system.

State function (State variables): When values of a system is independent of path followed and depend only on initial and final state, it is known as state function, e.g., ∆U, ∆H, ∆G etc.

Path function: These depend upon the path followed, e.g., work, heat, etc.


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