P-V Diagram — Four Processes Starting from the Same State
V P ($P_{1}$,$V_{1}$,$T_{1}$) Isobaric P=const Isothermal PV=k Adiabatic PV^γ=k Isochoric V=const Area under curve = Work (W) Adiabatic steeper than Isothermal (γ > 1)Process Comparison Table
| Process | Constant | Q | W | PV Curve | |
|---|---|---|---|---|---|
| Isothermal | T | nRT ln(/) | nRT ln(/) | 0 | Hyperbola |
| Adiabatic | Q = 0 | 0 | nCᵥ(−) | nCᵥ(−) | Steeper hyperbola |
| Isochoric | V | nCᵥ | 0 | nCᵥ | Vertical line |
| Isobaric | P | nCₚ | nR | nCᵥ | Horizontal line |
Gas Properties Table
| Gas Type | Examples | f | Cᵥ | Cₚ | γ |
|---|---|---|---|---|---|
| Monoatomic | He, Ne, Ar | 3 | 3R/2 | 5R/2 | 5/3 = 1.67 |
| Diatomic | , , | 5 | 5R/2 | 7R/2 | 7/5 = 1.40 |
| Polyatomic | C, O | 6 | 3R | 4R | 4/3 = 1.33 |
Molecular Speed Reference
| Speed | Formula | Value for at 300 K | Ratio |
|---|---|---|---|
| v_mp | √(2RT/M) | 394.8 m/s | 1.000 |
| v_avg | √(8RT/πM) | 445.5 m/s | 1.128 |
| v_rms | √(3RT/M) | 483.6 m/s | 1.224 |