The key difference between closed system and open system is that in a closed system, the matter does not exchange with the surrounding but, the energy exchanges with the surrounding whereas in an open system, both matter and energy exchanges with the surrounding.
For the purpose of chemistry, we can divide the universe into two parts; “system” and “the surrounding”. A system can be an organism, a reaction vessel or even a single cell. There are boundaries between a system and the surrounding. The scope of the system depends on these boundaries. Sometimes matters and energy exchanges through these boundaries. We can distinguish the systems by the kind of interactions they have or by the types of exchanges take place. Moreover, we can classify these systems into two as open systems and closed systems.
CONTENTS
1. Overview and Key Difference
2. What is a Closed System
3. What is an Open System
4. Side by Side Comparison – Closed System vs Open System in Tabular Form
5. Summary
What is a Closed System?
If matter does not transfer through the boundary, then we call that kind of system as a closed system. However, in a closed system energy exchanges with the surroundings. The matter inside a closed system is always the same. When a reaction happens, the system can expand, or it can transfer energy to the surrounding if it is at a lower temperature. For example, when there is a fluid compressed in a piston, it is a closed system. There the mass of the fluid doesn’t change, but the volume may change.
Figure 01: System and its Boundary in Contact with the Surrounding
An isolated system is also a closed system. However, it differs from a closed system, because the isolated system has neither mechanical nor thermal contact with its surrounding. With the time, isolated systems reach thermodynamic equilibrium by balancing the pressure, temperature or other differences.
What is an Open System?
In an open system, the matter and energy transfers through the boundary between the system and the surrounding. Since it is open, it continuously interacts with the surrounding. For example, our body is an open system. It is hard to control the energy flow in and out of an open system. Furthermore, the energy balance is also difficult. Since it is open, the mass of the system is not necessarily constant; rather its volume is constant.
Figure 01: First law of Thermodynamics: Open System
First law of thermodynamics relates to open systems. It states about the internal energy of an open system. We can change the internal energy of a system either by doing work on the system or heating. The change in internal energy of an open system is equal to the amount of energy that we need to add to the system (by means of heating or doing work) minus amount lost by matter flowing out and energy loss due to work was done by the system.
What is the Difference Between Closed System and Open System?
If the matter does not transfer through the boundary, then that kind of system is a closed system. Whereas, in an open system, both the matter and energy transfers through the boundary between the system and the surrounding. Therefore, the key difference between closed system and open system is that the closed systems do not allow any exchange of matter between the system and surrounding while the open system allows the exchanges of matter. Furthermore, another difference between closed system and open system is that the closed systems have a constant mass whereas the open systems have a varying mass.
Moreover, there is also a difference between closed system and open system in controlling the factors. That is, unlike in closed system, in a open system it is difficult to control the energy flow and other parameters.
Summary – Closed System vs Open System
A system is a part which occurs in the surrounding. There are different types of contacts between the system and the surrounding. Accordingly, there are two systems; an open system and a closed system. The key difference between closed system and open system is that in a closed system, the matter does not exchange with the surrounding but, the energy exchanges with the surrounding whereas in an open system, both matter and energy exchanges with the surrounding.
Reference:
1. Libretexts. “A System and Its Surroundings.” Chemistry LibreTexts, Libretexts, 21 July 2016. Available here
Image Courtesy:
1.”System boundary”By Wavesmikey, traced by Stannered (Public Domain) via Commons Wikimedia
2.”First law open system” (Public Domain) via Commons Wikimedia