3.2

Work Done by a System

  • Front: How is the infinitesimal work ($dW$) done by a gas during a volume change defined?

  • Back: $dW = p \, dV$, where $p$ is pressure and $dV$ is the change in volume.

  • Front: What is the formula for the net work ($W$) done by a system during a finite volume change?

  • Back: $W = \int_{V_1}^{V_2} p \, dV$.

  • Front: What is a quasi-static process?

  • Back: A process that occurs in infinitesimally small steps, keeping the system in thermal equilibrium.

  • Front: On a $pV$ diagram, what represents the work done by a gas?

  • Back: The area under the curve of the $pV$ graph.

  • Front: Is the work done by a system path-dependent or path-independent?

  • Back: Work is path-dependent; different thermodynamic paths between two states result in different amounts of work.

  • Front: What is the sign of work ($W$) when a gas expands?

  • Back: Positive ($W > 0$).

  • Front: What is the sign of work ($W$) when a gas is compressed?

  • Back: Negative ($W < 0$).

  • Front: How much work is done during a constant-volume (isochoric) process?

  • Back: Zero, because $dV = 0$.

Internal Energy

  • Front: What is the definition of internal energy ($E_{int}$)?

  • Back: The sum of the mechanical energies (kinetic and potential) of all molecules or entities within the system.

  • Front: What types of energy contribute to the internal energy of a molecule?

  • Back: Translational, rotational, and vibrational kinetic energy, plus potential energy from interatomic interactions.

  • Front: For an ideal monatomic gas, what constitutes the internal energy?

  • Back: Only translational kinetic energy, as there are no rotational/vibrational components or interatomic interactions.

  • Front: What is the formula for the internal energy ($E_{int}$) of $n$ moles of an ideal monatomic gas?

  • Back: $E_{int} = \frac{3}{2} nRT$.

  • Front: Does the internal energy of an ideal monatomic gas depend on pressure or volume?

  • Back: No, it depends strictly on the temperature.