Some Thermodynamics and Their Definitions

Thermodynamics is the branch of physical science that deals with the relations between heat and other forms of energy (such as mechanical, electrical, or chemical energy), and, by extension, of the relationships between all forms of energy. Some Thermodynamics and Their Definitions are given below.

System

The part of the universe which is under study is called the system. A system may be very simple like water is taken in a beaker or may be very complex like the digestion of food.

Surrounding Environment

The rest part of the universe or environment around the system is called the surrounding. Surrounding means all other things that can interact with the system.

Boundary

Anything which separates the system from the surrounding is called boundary.

Depending upon a system that interacts with the surrounding system may be classified into 3 types.

     1)Close system

    2) Open system

     3) Isolated system

• Close system
  The system in which energy (heat or work) is exchanged toward surrounding but not the matter or mass is called a closed system. For example, hot tea is taken in a closed metallic container where the heat can exchange but not the mass
• Open system
  The system in which both energy as well as mass can be exchanged towards the surrounding is called an open system. Example: addition of hydrochloric acid with pieces of CaCO3 in an open beaker where energy (heat), as well as mass (CO2), are exchanged towards the surrounding.
• Isolated system
  The system in which neither energy nor mass can be exchanged towards the surrounding is called an isolated system. Example: a perfectly Thermo flask where neither energy (heat) nor mass are exchanged.
  
  Iso-thermal System
  The system which is maintained at constant temperature is called an isothermal system.
  
  Adiabatic System
  A system that does not exchange heat towards the surrounding is called an adiabatic system.

State of a System
The parameters or properties which determine the state of the systems are pressure, temperature, volume, mass, and composition. These parameters are called state variables because any change in these parameters will also change the state of a system.

State function
A physical quantity is said to be a state function if its magnitude depends on the state of a system (initial and final) but not upon the path by which it has been reached.
state variables are of two types
1) Extensive properties
2) Intensive properties

1) Extensive Properties
Properties of a system whose magnitude depends upon the mass or quality of the substance are called extensive properties. For example mass, length, volume, etc.

2)Intensive Properties
Properties of a system whose magnitude doesn’t depend upon the mass or quantity of the substance are called intensive properties. For example temperature, refractive index, etc.

Therefore these are some definitions of thermodynamics.