It can be defined as the science which deals with the relation between heat, work and properties of the system.
Use of Thermodynamics:
Designing work producing machine – Heat engine, Steam engine, Gas turbine
Designing work Absorbing machine – Refrigerator,Air compressor
No work transfer systems - boiler, condenser,furnace.
Where no work is transferred, the Thermodynamic problem involve the use of heat to produce the change in state or the transfer of mass with a chemical reaction, as in the combustion of a fuel.
It can be defined as a definite quantity of matter, which is bounded by a closed surface.
Anything other than a system are called surroundings