Open System in Thermodynamics

What is Thermodynamics?

Thermodynamics refers to the study of the transfer of energy that occurs in molecules or collections of molecules. When we are discussing thermodynamics, the particular item or collection of items that we’re interested in is called the system, while everything that's not included in the system we have defined is called the surroundings. For instance, if you were heating a pot of water on the stove, the system might include the stove, pot, and water, while the environment would be everything else: the universe, galaxy, planet, country, neighbourhood, house, and rest of the kitchen. The system and therefore the surroundings together structure the universe. Let us define what an open system.

There are three sorts of systems in thermodynamics: open, closed, and isolated.

  1. An open system can exchange both matter and energy that is present with its surroundings. The stovetop example would be an open system because heat and water vapour are often lost to the air.

  2. A closed system, on the opposite hand, can exchange only energy with its surroundings, not matter. From the previous example, if we put a very tightly fitting lid on the pot, it would approximate a closed system.

  3. An isolated system is one that can't exchange either matter or energy with its surroundings. A perfect isolated system is tough to return by, but an insulated drink cooler with a lid is conceptually almost like a real isolated system. The items inside can exchange energy with one another, which is why the drinks get cold, and therefore the ice melts a touch, but they exchange little or no energy with the outside environment.

What is an Open System in Thermodynamics?

An open system may be a system that has external interactions. Such interactions can take the shape of data, energy, or material transfers into or out of the system boundary, counting on the discipline which defines the concept. An open system is contrasted with the concept of an isolated system that exchanges neither energy and matter nor information with its environment. An open system is additionally referred to as a flow system.

For an example of open system in thermodynamics, the earth can be recognized as an open system. In this case, the world is that the system and space is that the surrounding. Sunlight can reach the world’s surface and that we can send rockets to space. Sunlight and rocket are often explained as energy and matter, respectively.

Exchange of matter between the open system and the surrounding occurs easily. This can even be easily explained by adding matter or removing matter. But energy exchange may be a bit more complicated because energy is often exchanged in several forms and different conversions may occur during this exchange. Energy is exchanged as heat or the other form.

In thermodynamic terms, the energy exchange is characterized by P.E, K.E, and thermal energy. Potential energy is the stored energy. Kinetic energy is the energy-carrying by an object while moving. However, the energy of a system always exists in one among these three states or in two states at an equivalent time. For example, a stationary object can exchange heat with the encompassing. Then it's both P.E. and thermal energy. Energy is often exchanged or transferred as P.E. or K.E. But sometimes, P.E is often converted into K.E or the other can occur. Thermal energy or heat is additionally exchanged between open systems and their surroundings.

Due to the potential of exchanging matter between an open system and surrounding, the interior mass of an open system varies with time. If the matter is added, then an increase in the mass can be found and if the matter is removed, then The first decrease in the mass is found.

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First Law of Thermodynamics For an Open System

The first law of thermodynamics thinks big: It deals with the entire amount of energy within the universe, and especially, it states that this total amount doesn't change. Put differently, the primary Law of Thermodynamics states that energy can't be created or destroyed. It can only change shape or be transferred from one object to a different one.

This law could seem quite abstract, but if we start to see examples, we’ll find that transfers and transformations of energy happen around us all the time. 

For Example:

  • Light bulbs convert electricity into light energy (radiant energy).

  • One ball hits another, transferring K.E. and making the second ball move.

  • Plants convert the energy of sunlight (radiant energy) into energy stored in organic molecules.

Importantly, none of these transfers is completely efficient. Instead, in each scenario, a number of the starting energy is released as thermal energy. When it's moving from one object to different, thermal energy is named by the more familiar name of warmth. It's obvious that glowing light bulbs generate heat additionally to light, but moving pool balls do too, as do the inefficient energy transfers of plant and animal metabolism. To see why this heat generation is vital, stay tuned for the Second Law of Thermodynamics.

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Difference Between the Open System and Closed System in Thermodynamics

Open System

Closed System

An open system is a type of thermodynamic system where the energy and matter are often exchanged with its surrounding.

A closed system is a type of thermodynamic system where only the energy can be exchanged with its surrounding but not matter.

Open systems can exchange matter with the surrounding.

Closed systems cannot exchange matter with the surrounding.

In the case of open systems, the mass of the system will vary with time.

In the case of closed systems, the mass of the system is constant.

Open systems have boundaries that are not closed.

The boundary of a closed system is totally closed.


The interactions between systems and their surroundings can be found everywhere in the environment. Systems can be divided into opened, closed, or isolated systems. The main difference between open and closed systems is in the case of an open system, matter can be exchanged with the surroundings whereas, in the case of a closed system, matter cannot be exchanged with the surroundings.

FAQs (Frequently Asked Questions)

1. What is an Open System in Thermodynamics?

Ans: Open system is a type of thermodynamics in which the exchange of matter and energy takes place in between the surrounding environment. 

2. It is Said That in an Open System Work Is Done. How?

Ans: In the case of an open system, the transfer of energy takes place in three forms according to the first law of thermodynamics as in the form of work, in the form of heat, or in the form of energy that is associated with the matter. 

The material that is present in the system = Amount of material entering the system - Amount of materials leaving the system.

E inside the system = E in - E out