Closed System vs Open System
For the purpose of chemistry, the universe is divided into two parts. The part we are interested is called a system, and the rest is called 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 is defined by these boundaries. Sometimes matters and energy can be exchanged through these boundaries. The systems are distinguished by the kind of interactions they have or by the types of exchanges take place. The systems can be classified into two as open systems and closed systems.
In an open system, the matter and energy can be transferred 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. Further, energy balance is also difficult. Since it is open, the mass of the system is not necessarily being constant; rather its volume is constant. First law of thermodynamics is associated with open systems. It states about the internal energy of an open system. The internal energy of a system may be changed 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 added to the system (by means of heating or doing work) minus amount lost by matter flowing out and energy loss due to the work done by the system.
If the matter cannot be transferred through the boundary, then that kind of system is called a closed system. However, in a closed system energy can be exchanged 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, a closed system is where fluid is compressed in a piston. There the mass of the fluid doesn’t change, but the volume may change.
Isolated system is also a closed system. However, it differs from a closed system, because isolated system has neither mechanical nor thermal contact with its surrounding. With the time, isolated systems reach thermodynamical equilibrium by balancing the pressure, temperature or other differences.
What is the difference between Closed System and Open System?
• In a closed system, matter cannot be exchanged with the surrounding; however, energy can be exchanged. But in an open system, both matter and energy can be exchanged with the surrounding. Therefore, closed system is somewhat restricted than an open system.
• In a closed system, the mass inside is constant throughout a process. But in an open system, mass is not necessarily be constant. We can say that the volume is constant in an open system.
• The processes, energy flow and other parameters of a closed system can be controlled than those in an open system.