Preliminary Concepts In Thermodynamics: Terminologies In Thermodynamic

As we have seen earlier that whenever there is an interaction between two forms of energy or between energy and matter, thermodynamics will be involved. 
"Thermodynamics can be defined as the study of energy, energy changes and its relation to matter". 
For Example- 
Heating/ Air-conditioning system, Refrigerators, etc. 

The preliminary concept of thermodynamics is nothing but the language of thermodynamics. The language of thermodynamics means that when we define the thermodynamic behaviour of an object, we utilise a set of terminology to investigate that object's thermodynamic behaviour. 
These terminologies are - System & Surrounding & Boundary & Universe, etc.
In this article, we will learn about these all terminologies in detail with the help of suitable examples.

 
Let Us Now Define Them One By One;
OR

(1) System
"A system is defined as a fixed three dimensional region in space, selected for the study or analysis". Usually, we consider only one system at a time. 
We can define a system in other ways like;
(a) A system is a region where we focus our attention.
(b) A part of the universe that is chosen for the thermodynamic study.
(c) A definite area in space where some thermodynamic process takes place.
For Example- 
A molten ice cube, Water boiled in a bowl, Fluid filled inside a pipe, Water on one side of a heat exchanger, A gas balloon, etc.

(2) Surrounding
"The mass or region outside the system is called surrounding". In other words, we can say that everything around the system that interacts with the system is called the surrounding.
For Example- 
An automobile engine in which burning gasoline is a system while everything else (such as pistons, exhaust systems, radiators, outside air, etc.) is surrounding.
☆ Generally, the region of the universe that surrounds the system is called the surrounding.

(3) Boundary
"A boundary is defined as a real or imaginary surface that seperate the system from its surrounding". This surface (or boundary) can be fixed or movable.

(4) Universe
A universe is defined as the summation of our system and surrounding. In other words, we can say that the combination of system and the surroundings together is usually referred to as universe.

NOTE
Generally, Whenever there is energy transfer between the system and the surrounding, this energy transfer between the system and the surrounding takes place in two ways: Work Transfer and Heat Transfer, from system to surrounding or from surrounding to system. 


System, Surrounding, Boundary And Universe 
(1) We define all these terms in a single sentence. In thermodynamics, the System refers to the part of the universe on which experiments are performed and the rest is called the Surroundings. 
The surrounding includes everything except the system. System and surrounding together make up the Universe. The entire universe except the system is not affected by the changes taking place in the system. That is why, for experimental work that part of the universe that interacts with the system is taken as the surrounding. And the wall that separates the system and the surroundings is called the Boundary.
(2) Let's discuss the system, surroundings, boundary and universe by taking an example of the flask containing liquid inside it.
The region which is inside the flask is known as a "SYSTEM". The region which is outside the flask is known as "SURROUNDING". And the imaginary line which separates the system and surrounding is known as a "BOUNDARY". Now, finally the "UNIVERSE" is nothing but a combination of flask as well as its surroundings.


FAQs
What Is Homogeneous System??
When a system is a uniform throughout or consists of a single phase, it is said to be the homogeneous system. 
Examples- A pure single Solid, liquid & a gas, a mixture of gases.
What is a heterogeneous system??
A heterogeneous system is one which is not uniform throughout and which contains two or more phases which are separated from one another by definite boundary surface.
Examples- Two immiscible liquids such as benzene and water.



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