What is Thermodynamics?

Thermodynamics is a branch of physics which deals with the energy and work of a system. It was born in the 19th century as scientists were first discovering how to build and operate steam engines. Thermodynamics deals only with the large scale response of a system which we can observe and measure in experiments. Small scale gas interactions are described by the kinetictheory of gases. The methods complement each other; some principles are more easily understood in terms of thermodynamics and some principles are more easily explained by kinetic theory. 

Credit: http://www.grc.nasa.gov

Heat and Energy

Energy is the ability to do work on matter. Heat or, thermal energy is the total energy associated with random atomic and molecular motions of a substance. Read more here.

 Courtesy: Ritter, Michael E., The Physical Environment: an Introduction to Physical Geography.

Thermodynamics - Introduction

Thermodynamics is a macroscopic theory. It deals with the bulk properties of matter. It does not concern itself with whether or not there are atoms or molecules. In fact, thermodynamics does not care whether or not there are atoms and molecules. Thermodynamics is the study of the patterns of energy change. Thermodynamics refers to energy, and "dynamics" means the patterns of change. Specifically the study of thermodynamics deals mainly with (1) energy conversion and (2) the stability of molecules and direction of change.

On the other hand, quantum mechanics is a microscopic theory because it deals with the individual particles of matter. 

Statistical thermodynamics brings us full circle by providing a mechanism for calculating the properties of bulk material (macroscopic samples) from the properties of the atoms and molecules which comprise the material. 

Credit: http://fisitech.wordpress.com/content/thermodynamics/

Courtesy: W. R. Salzman (http://www.chem.arizona.edu) and http://thinkquest.org

Born Haber Cycle for NaCl

 Courtesy: Dr. Mike Thompson