Question

In a thermodynamic study a scientist focuses on the properties of a solution in an apparatus as illustrated. A solu- tion is continuously flowing into the apparatus at the top and out at the bottom, such that the amount of solution in the apparatus is constant with time. (a) Is the solution in the apparatus a closed system, open system, or isolated system? Explain your choice. (b) If it is not a closed system, what could be done to make it a closed system?

Short answer

(a) The solution in the apparatus is an open system because it allows mass to be exchanged with the surroundings. (b) To turn the open system into a closed system, the flow of the solution into and out of the apparatus should be stopped, allowing only energy (heat and work) exchange with the surroundings without mass exchange.

Step-by-step solution

Review the definitions of different types of systems

Thermodynamic systems can be classified into three categories: 1. Open system: A system that allows both mass and energy (heat and work) to be exchanged with the surroundings. 2. Closed system: A system that allows only energy (heat and work) to be exchanged with the surroundings but not mass. 3. Isolated system: A system that does not allow the exchange of mass and energy with the surroundings.

Analyze the properties of the flowing solution

The given problem states that the solution continuously flows into the apparatus at the top and out at the bottom. As a result, mass (the solution) is exchanged between the system (the solution inside the apparatus) and the surroundings. Therefore, it can't be a closed or an isolated system.

Identify the type of system

Since the flowing solution in the apparatus exchanges mass with the surroundings, it falls under the category of an open system. Thus, the solution in the apparatus is an open system.

Answer (a)

The solution in the apparatus is an open system because it allows mass to be exchanged with the surroundings.

Modify the system to become a closed system

To transform the open system into a closed system, making sure that the mass exchange between the solution inside of the apparatus and the surroundings is prohibited. To achieve that, the flow of the solution into and out of the apparatus must be stopped, allowing only energy exchange (heat and work) with the surroundings.

Answer (b)

In order to turn the open system into a closed one, the flow of the solution into and out of the apparatus should be stopped, allowing only energy (heat and work) exchange with the surroundings without mass exchange.

Key concepts

Open System

In thermodynamics, an open system plays a crucial role in understanding how substances interact with their environment. An open system is defined by its ability to transfer both mass and energy across its boundaries. This means that substances can enter or leave the system, while energy in the form of heat or work can also be transferred.

For instance, boiling water in a pot without a lid is a classic example of an open system; steam (mass) escapes, and heat can be transferred to the surroundings. In the exercise described, the apparatus with the flowing solution is an open system as well, since the solution enters and exits the system continuously.

Closed System

A closed system, by contrast, allows for the transfer of energy but not mass. This is a key distinction from an open system. In a closed system, no matter enters or leaves the system's boundaries, but energy in the form of heat or work can be exchanged with the surroundings. An example could include a sealed container that can transfer heat with its environment but contains a fixed amount of gas.

In the context of the exercise, to convert the apparatus from an open to a closed system, one would need to seal the system such that no solution can enter or exit while still allowing for heat to be transferred.

Isolated System

The most restrictive of the thermodynamic systems is the isolated system. It neither exchanges mass nor energy with its surroundings. Think of it as a perfectly insulated box that neither loses nor gains heat, and nothing inside it can escape, nor can anything outside get in.

Although theoretically ideal, perfect isolated systems do not exist in reality due to the ever-present nature of energy transfer. However, a thermos flask is a good real-world approximation, as it minimizes both mass and heat exchange with its surroundings. In the exercise, such a system would not allow the solution to flow in or out, and there would be no energy exchange with the environment.

Mass and Energy Exchange

Mass and energy exchange is the bedrock upon which thermodynamic processes are built. The laws of thermodynamics govern how energy is conserved and how entropy, a measure of disorder, increases with time.

Mass exchange involves the transfer of substances between a system and its environment, while energy exchange includes heat and work interactions. In the exercise, the continuous flow of the solution into and out of the apparatus is a clear demonstration of mass exchange. Energy exchange, while not explicit in the exercise, would play a part if the apparatus transferred heat with the surroundings.

Thermodynamic Study

A thermodynamic study involves analyzing systems under the laws of thermodynamics to understand energy and mass transfer, and the changes they induce in system properties like temperature and pressure.

Such studies revolve around understanding these systems' behavior under different conditions, thus enabling the design of efficient systems in engineering and predicting natural processes in science. In the context of the exercise, a thermodynamic study of the solution in the apparatus focuses on how the solution's properties might be affected by its continuous flow and interaction with the surroundings.