The key difference between isolated system and closed system is that the isolated systems cannot exchange both matter and energy with the surrounding but, though the closed systems too cannot exchange matter with the surrounding, it can exchange the energy.
For the easiness of studying chemistry, we divide the universe into two parts. The part we are going to study is the “system”, and the rest is the “surrounding”. For instance, a system may be an organism, a reaction vessel or even a single cell. There is a boundary between a system and the surrounding. The boundary defines the scope of the system. Sometimes, the matter and energy exchange through these boundaries. Furthermore, we can classify a system into two categories; they are the open system and closed system. An isolated system is a form of a closed system.
CONTENTS
1. Overview and Key Difference
2. What is Isolated System
3. What is Closed System
4. Side by Side Comparison – Isolated System vs Closed System in Tabular Form
5. Summary
What is Isolated System?
An isolated system is a form of a closed system. But, it differs from a closed system because it has neither mechanical nor thermal contact with its surrounding. That means; the isolated systems cannot exchange both matter and energy with the surrounding. Further, these systems reach thermodynamical equilibrium with time, by balancing the pressure, temperature, or other parameters.
Practically, an isolated system does not exist because all the things are interacting with one another in certain ways. However, we can consider the whole universe as an isolated system, considering there is no transferring of matter and energy outside the universe. Theoretically, this is useful when constructing models. For example, the first and second thermodynamic laws describe an isolated system.
Figure 01: Comparison of Isolated System with Open and Closed Systems
The first law of thermodynamics states that the “internal energy of an isolated system is constant.” The second law of thermodynamics says that “the entropy of an isolated system increases in the course of a spontaneous process.” However, this law is only true for isolated systems. The entropy will increase over time in an isolated system and will reach the maximum value at the equilibrium. In brief, the overall energy of these systems can never increase. Thus, the entropy can never decrease.
What is Closed System?
In a closed system, matter cannot pass through the boundary. Therefore, the matter inside a closed system is always the same. However, in this type of system, the energy exchanges with the surrounding. For example, when a reaction happens, the system can expand, or it can transfer the energy to the surrounding if it is at a lower temperature.
Figure 02: A System and its surrounding separated by a Boundary
Ex: If we cover the top of a warm cup of tea with a lid, then it becomes a closed system. There, the steam cannot escape the system. Also, the gas molecules in the surrounding cannot enter the system. Hence, there is no exchange of matter. However, the heat of the tea exchanges with the surrounding. We can feel the heat if we touch the lid of the cup. Therefore the energy comes outside as thermal energy. There, the system attains an equilibrium with the surrounding when the temperature inside and outside of the system becomes equal.
What is the Difference Between Isolated System and Closed System?
A boundary separates a system and its surrounding. We can name a system as either an open or a closed system depending on the exchange of matter and energy through this boundary. An isolated system is also a form of a closed system. The key difference between isolated system and closed system is that the isolated systems cannot exchange both matter and energy with the surrounding but, though the closed systems cannot exchange matter with the surrounding, it can exchange the energy.
As another important difference between isolated system and closed system, we can say that the entropy of an isolated system can never decrease while the entropy of a closed system can decrease. Moreover, isolated systems are theoretical; that means, these systems do not exist in reality. However, closed systems exist in reality.
Summary – Isolated System vs Closed System
Systems are of two types; they are the open system and closed system. Isolated systems are also a type of closed system. However, there are few differences between them. The key difference between isolated system and closed system is that the isolated systems cannot exchange both matter and energy with the surrounding but, though the closed systems too cannot exchange matter with the surrounding, it can exchange the energy.
Reference:
1. Helmenstine, Anne Marie, Ph.D. “Closed System Definition (Science).” ThoughtCo, Jun. 22, 2018. Available here
2. Helmenstine, Anne Marie, Ph.D. “Isolated System Definition.” ThoughtCo, Jul. 12, 2017. Available here
Image Courtesy:
1.”Diagram Systems”By Alkh.Alwa – Own work, (CC BY-SA 4.0) via Commons Wikimedia
2.”System boundary”By Wavesmikey, (Public Domain) via Commons Wikimedia