Difference Between Adiabatic and Isolated System

Main Difference – Adiabatic vs Isolated System

In physical chemistry,  a system is a part of the universe which is being studied, and surrounding is the rest of the universe other than that particular system. In some systems, there are interactions between the system and the surrounding. But some systems have no connection between the system and the surrounding. Adiabatic systems and isolated systems are two types of systems. Both these systems show no exchange of energy or matter with the surrounding. But these systems are different from each other. The main difference between adiabatic system and isolated system is that an adiabatic system has an environment around it whereas an isolated system has no environment around it.

Key Areas Covered

1. What is an Adiabatic System
      – Definition, Explanation with Examples
2. What is an Isolated System
      – Definition, Explanation with Examples
3. What is the Difference Between Adiabatic and Isolated System
      – Comparison of Key Differences

Key Terms: Adiabatic System, Energy, Isolated System, Surrounding, System

What is an Adiabatic System

An adiabatic system is a system that has no exchange of energy or matter with the surrounding environment. This means energy is not either lost or gained by the adiabatic system. These systems are known to be adiabatically isolated systems. According to the first law of thermodynamics,

∆U   =    Q   –   W

Where U is the internal energy of the system,

              Q is the energy that is exchanged between system and its surrounding,

              W is the work done by the system on its surrounding.

For an adiabatic system, Q = 0. Then,

∆U   =   – W

If we consider a system that is composed of a mixture of gases that act as an adiabatic system when it is expanded, the value of W is positive, and the internal energy is decreased. But if the system contracts, the value of W is negative, and the internal energy is increased. This indicates that energy in an adiabatic process is transferred to its surroundings only as work.

Figure 1: A System

Some systems with certain chemical reactions can be approximately considered as adiabatic systems because these reactions happen rapidly, not giving it enough time to release energy outside or gain energy from outside.

What is an Isolated System

An isolated system is a system that has no transfer of energy and matter through its boundaries and has no surrounding environment. An isolated system can be defined in a different manner as, a system that is separated from other systems so that no interaction exists between this isolated system and other systems.

Figure 2: Comparison of Open System and Closed System with Isolated System

An isolated system is different from a closed system since a closed system only denies the transfer of matter, not energy. But isolated systems do not allow even energy to escape or enter the system. An isolated system obeys the conservation law. It indicates that the energy and matter stay constant inside the system.

Difference Between Adiabatic and Isolated System

Definition

Adiabatic System: An adiabatic system is a system that has no exchange of energy or matter with the surrounding environment.

Isolated System: An isolated system is a system that has no transfer of energy and matter through its boundaries and has no surrounding environment.

Surrounding

Adiabatic System: Adiabatic systems have a surrounding environment.

Isolated System: Isolated systems have no surrounding environment.

Energy Exchange

Adiabatic System: Adiabatic systems do not gain or lose energy but internal energy can be changed due to work done by the system.

Isolated System: The energy of an isolated system is conserved.

Internal Energy

Adiabatic System: The internal energy of an adiabatic system can be changed.

Isolated System: The internal energy of an isolated system cannot be changed.

Conclusion

When explaining the behavior of a system thermodynamically, we use several types of systems considering their interactions with the surrounding. Adiabatic and isolated systems are such two types that are used to explain the systems that do not show the transfer of energy or matter with their environment. The main difference between adiabatic system and isolated system is that an adiabatic system has an environment around it whereas an isolated system has no environment around it.

References:

1. Jones, Andrew Zimmerman. “Keeping It Cool: The Adiabatic Process of Thermodynamics.” ThoughtCo, Available here. Accessed 29 Sept. 2017.
2. “Adiabatic Process.” Adiabatic Processes, Available here. Accessed 29 Sept. 2017.