11/12.2 First Law of Thermodynamics
Internal Energy – The kinetic and potential energy associated with a system of particles.
First Law of Thermodynamics - Conservation of Energy
Energy cannot be created or destroyed.
ΔU = q + w q = heat w = work
PV Work – Pressure-Volume work
Work equals the area under the curve of P vs V
Constant Volume Heat Capacity
Constant Pressure Heat Capacity
| CV and CP for Ideal Gases | |||
|---|---|---|---|
| Gas | f | CV | CP |
| Monatomic (ex. He) | 3 | 3/2 R | 5/2 R |
| Linear (ex. O2) | 5 | 5/2 R | 7/2 R |
| Nonlinear (ex. CH4) | 6 | 3 R | 4 R |
*Vibrational Degrees of Freedom not included
| FIRST LAW OF THERMODYNAMICS FOR IDEAL GASES | |||
|---|---|---|---|
| ΔU | q | w | |
| IsobaricΔP = 0 | nCVΔT | nCPΔT | -PΔT |
| IsochoricΔV = 0 | nCVΔT | nCVΔT | 0 |
| Adiabaticq = 0 | nCVΔT | 0 | ΔU |
| IsothermalΔT = 0 | 0 | -w | -nRTln Vf / Vi |