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Thermodynamic process; constant pressure heating diagrams

Short answer

A thermodynamic process is the path of successive equilibrium states a system passes through. For constant-pressure heating of an ideal gas: P-V diagram is a horizontal line; T-V is a straight line through origin; P-T is a horizontal line.

Define thermodynamic process. Sketch P-V, T-V, and P-T diagrams for an ideal gas undergoing constant pressure heating process.

A thermodynamic process is the path of successive states through which a system passes when it changes from one equilibrium state to another, e.g. constant pressure (isobaric), constant volume, constant temperature, adiabatic.

Constant-pressure heating of an ideal gas

Here P = constant, so from PV = mRT, V/T = constant: V ∝ T. Volume increases as the gas is heated.

 P-V diagram        T-V diagram        P-T diagram
 P|                 T|        /        P|
  | 1 ------> 2      |      / 2         | 1 ------> 2
  |                  |    /             |
  |                  |  / 1             |
  +--------- V       +--------- V       +--------- T
 horizontal line    straight line      horizontal line
                    through origin
  • P-V: horizontal straight line from V₁ to V₂ (V₂ > V₁); area under it = P(V₂ − V₁) = work done.
  • T-V: straight line passing through the origin (Charles' law).
  • P-T: horizontal straight line parallel to the T axis.

✓ Answer checked by Claude Opus 5.5 (high effort)

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