Thermodynamics
It is the the branch of science which deals with study of heat and work and those properties of matter that relate to heat and work.
Thermodynamic system
A system is defined as a quantity of matter or a region in space chosen for study. The mass or region outside the system is called the surroundings
Boundary: the real or imaginary surface that separates the system from its surroundings. The boundaries of a system can be fixed or movable. Mathematically, the boundary has zero thickness, no mass, and no volume.
Fig. Universe composed of a system, its surroundings, and the system boundary
Types of Systems
• Closed system or control mass
consists of a fixed amount of mass, and no mass can cross its boundary. But, energy in the form of heat or work, can cross the boundary, and the volume of a closed system does not have to be fixed.
• Open system or control volume
is a properly selected region in space. It usually encloses a device that involves mass flow such as a compressor. Both mass and energy can cross the boundary of a control volume.
• Isolated system
A closed system that does not communicate with the surroundings by any means.
• Adiabatic system
A closed or open system that does not exchange energy with the surroundings by heat.
Energy
In thermodynamics, we deal with change of the total energy only. Thus, the total energy of a system can be assigned a value of zero at some reference point. Total energy of a system has two groups: macroscopic and microscopic.
Macroscopic forms of energy
Forms of energy that a system possess as a whole with respect to some outside reference frame, such as kinetic and potential energy.
Microscopic forms of energy
are those related to molecular structure of a system. They are independent of outside reference frames. The sum of microscopic energy is called the internal energy, U
Properties of a System
Any characteristic of a system is called a property.
Intensive properties
are those that are independent of the size (mass) of a system, such as temperature, pressure, and density. They are not additive.
Extensive properties
values that are dependent on size of the system such as mass, volume, and total energy U.
Processes and Cycles
Any change a system undergoes from one equilibrium state to another is called a process, and the series of states through which a system passes during a process is called a path.
