Pressure-volume work

Definition

Pressure-volume work, also known as PV work, is the work done by a system as it expands or contracts against an external pressure. It represents the energy transfer between a system and its surroundings due to changes in the system's volume.

5 Must Know Facts For Your Next Test

1. Pressure-volume work is a type of mechanical work that is performed when a system changes its volume against an external pressure.
2. The mathematical expression for pressure-volume work is $W = \int_{V_i}^{V_f} P \, dV$, where $W$ is the work done, $P$ is the pressure, and $dV$ is the change in volume.
3. Pressure-volume work can be positive or negative, depending on whether the system is expanding or contracting, respectively.
4. For a reversible process, the pressure-volume work is the area under the pressure-volume curve on a $P$-$V$ diagram.
5. Pressure-volume work is one of the two main types of work that can be done on or by a thermodynamic system, the other being heat transfer.

Review Questions

• Explain how pressure-volume work is related to the first law of thermodynamics.
  • According to the first law of thermodynamics, the change in the internal energy of a system is equal to the sum of the work done on the system and the heat added to the system. Pressure-volume work is a specific type of work that is done on or by a thermodynamic system as it changes its volume against an external pressure. This pressure-volume work is one of the key components that contribute to the overall change in the system's internal energy, as described by the first law of thermodynamics.
• Describe the relationship between pressure-volume work and the $P$-$V$ diagram for a reversible process.
  • For a reversible process, the pressure-volume work done on or by a system is represented by the area under the pressure-volume curve on a $P$-$V$ diagram. The mathematical expression for this work is $W = \int_{V_i}^{V_f} P \, dV$, where the integral represents the area under the curve between the initial volume $V_i$ and the final volume $V_f$. This relationship between the pressure-volume work and the area under the $P$-$V$ curve is a key concept in understanding the thermodynamics of reversible processes.
• Analyze the significance of pressure-volume work in the context of the first law of thermodynamics and the study of thermodynamic systems.
  • Pressure-volume work is a fundamental concept in the first law of thermodynamics and the study of thermodynamic systems. It represents the energy transfer between a system and its surroundings due to changes in the system's volume, which is one of the key ways that a system can exchange energy with its environment. Understanding pressure-volume work is crucial for analyzing the behavior of thermodynamic systems, as it allows for the quantification of the work done on or by the system and its relationship to the changes in the system's internal energy, as described by the first law of thermodynamics. This knowledge is essential for the study and application of thermodynamics in various fields, such as engineering, physics, and chemistry.

Related terms

First law of thermodynamics: The first law of thermodynamics states that the change in the internal energy of a system is equal to the sum of the work done on the system and the heat added to the system.

Thermodynamic system: A thermodynamic system is a defined region of space that is under consideration for a thermodynamic analysis, separated from its surroundings by a boundary.

Reversible process: A reversible process is a thermodynamic process that can be reversed without leaving any trace on the system or its surroundings.