The branch of science which deals with the study of different forms of energy and their interconversion is called thermodynamics. Thermodynamics is an important branch of science. It finds a large number of applications not only in chemistry but also in other branches of science, engineering and technology.
System:
A specific part of the universe which is under thermodynamics observation is called the system. A system is called homogeneous if the physical properties and chemical composition are identical throughout the system. On the other hand, a system is said to be heterogeneous if it consists of parts or phases each of which has different physical and chemical properties. Thus, a homogeneous system consists of one phase while a heterogeneous system consists of two or more phases.
Surroundings:
The remaining part of the universe which is not under a part of the system is called the surroundings. In other wards, surroundings include everything other than the system. The system and surroundings together constitute the universe.
Boundary:
The system and the surroundings are separated by real or imaginary line called boundary. The boundary also defines the limits of the system. The system and the surroundings can be interact across the boundary.
Types of systems:
System can be classified into three types depending upon the movement of matter and energy in or out of the system.
- Open System
- Closed System and
- Isolated System
1) Open System:
A system which can exchange matter as well as energy with the surrounding is called an open system. For example, hot coffee in an open flask is an example of open system because it can gain or lose mater as well as energy.
2) Closed System:
A system which can exchange energy but not mass with its surrounding is called a closed system. For example, hot coffee in a stainless flask is an example of closed system because energy can be gained or lost (through the steel walls) but not mater.
3) Isolated System:
A system which can neither exchange mass nor energy with the surroundings is called an isolated system. There is no perfectly isolated system. However, a system which is completely sealed to prevent inflow or outflow of matter and is thermally insulated to prevent flow of heat can be considered as an isolated system. For example, hot coffee in a corked thermos flask is an isolated system, because it can neither gain nor lose energy nor matter.
