Thermodynamics

S.GunabalanAssociate ProfessorMechanical Engineering DepartmentBharathiyar College of Engineering & TechnologyKaraikal - 609 609.e-Mail : gunabalans@yahoo.com

Thermodynamics

Thermodynamics is the science of energy transfer and its effect on the physical properties of substances.

Thermo = HEAT (or Energy)Dynamics: Movement

The Temperature - a quantity which indicates how hot or cold the body isTemperature is indicator of direction for heat flow.

Thermodynamics

Thermodynamics is the science of energy transfer and its effect on the physical properties of substances.

1. Macroscopic thermodynamics is only concerned with the effects of the action of many molecules, and these effects can be perceived by human senses.

2. The behaviour of the gas is described by summing up the behaviour of each molecule. Such a study is made in microscopic or statistical thermodynamics.

Thermodynamic System

• Thermodynamic system is defined as a region in space upon which attention is concentrated in the analysis of a problem.

surroundings : Everything external to the system is called the surroundings or the environment. boundary : The system is separated from the surroundings by the system boundary

Thermodynamic System

Thermodynamic SystemOpen system

http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodynamics/A_System_And_Its_Surroundings

A open system is defined when a fixed volume is under study. There can be mass transfers as well as energy transfers across the boundary.

Thermodynamic System

• Truly isolated systems cannot exist in nature, • The only possibility is the universe itself, • So its is a hypothetical concepts

http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodynamics/A_System_And_Its_Surroundings

isolated systems

Thermodynamic System

http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodynamics/A_System_And_Its_Surroundings

Closed systems

• A closed system is a system that exchanges only energy with its surroundings, not matter.

• Matter can no longer transfer because the lid prevents matter from entering the pan and leaving the pan. Still, the pan allows energy transfer.

A closed system always contains the same matter. There can be no mass transfers across the boundary. There may be energy transfer across the boundary.

Thermodynamic System

http://nptel.iitm.ac.in/courses/Webcourse-contents/IIT%20Kharagpur/Ref%20and%20Air%20Cond/R&AC%20Web%20files/R&AC%20Lecture%204/hyperlinks/systems.htm

Example the contents of a pressure cooker on a stove with its lid tightly closed and the whistle in position, is a closed system as no mass can enter or leave the pressure cooker, but heat can be transferred to it.

When the whistle of the pressure cooker blows, then it becomes an open system as steam leaves the cooker.

A perfectly insulated, rigid and closed vessel is an example of an isolated system as neither mass nor energy can enter or leave the system.

Properties

• Thermodynamic properties are observable or measurable properties of the system(pressure, temperature, volume)– Classification of properties

1. Intensive properties (Independent of mas)Properties have same value in any part of the system

and it is independent of mas (pressure, temperature)

2. Extensive properties (mas dependent)depends on mass of the system and de not maintain

same value across the system (mass, volume, enthalpy, energy)

State

The specific condition of the system is called State of the system.

the properties are used to describe the state of the system.Path : The succession of states passed through during a change of state is called the pathProcess: the path is completely specified, the change of state is called a process

Thermodynamic Equilibrium

• when no change in any macroscopic property then the system is in equilibrium

Applications of thermodynamics

•To predict the equilibrium state of a reactivemixture as well as the natural direction of change in a system not at equilibrium•thermodynamics can’t predict how long it takes for equilibrium to be reached

Reference

• Nag, P. K. 2002. Basic and applied thermodynamics. Tata McGraw-Hill, New Delhi.

• http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodynamics/A_System_And_Its_Surroundings

• http://nptel.iitm.ac.in/courses/Webcourse-contents/IIT%20Kharagpur/Ref%20and%20Air%20Cond/R&AC%20Web%20files/R&AC%20Lecture%204/hyperlinks/systems.htm ( date 25-june-2013)