Thermodynamics is a branch of physics that concerns the flow of heat energy and the ability to convert energy into work. Thermodynamics is also extensively used in chemistry, atmospheric science, geology and engineering.
Thermodynamics is a branch of yet a larger branch of physics called statistical mechanics, which brings thermodynamics closer to modern physics. In fact, the discovery of quantum mechanics was an outcrop of thermodynamics. Josiah Williard Gibbs first utilized a quantum approach to express chemical reactions. Max Planck then utilized a quantum approach to express energy levels in photons being edited from a hot object.
Motivation and Applications
An important motivation for thermodynamics was to understand how to make engines more efficient, and what the maximum efficiency for engines could be. Another application is to express the energy involved in chemical reactions.