Lecture 2

0th Law

There exists, for every thermodynamic system in equilibrium, a property called temperature. Equality of temperature is a necessary and sufficient condition for thermal equilibrium.

Celsius in Kelvin

Ideal Gas

• standard model of real gases, idelizaed.
• Properties:
  • No volume
  • kinetic energy only
  • All Colission elastic

→ Good approximation for low perssures

$p \cdot V = n\: R_m \: T = m \: R \: T$

formula is derived by the following findings

conversion of ideal gas to real gas

Compressibility factor $Z$:

$pV = ZRT$

$Z = \frac{\rho_{ideal}}{\rho_{real}}$

Ideal liquid

-standard model of real liquids, idelizaed. -incompressable, inviscid(zero viscoity)

=>change in pressure/tempertaure: aprrox. constant volume $V = const != f(T,p)$

Work

-form of energy transported over the system bondarys(except heat)

Volume/Displacement work

Displacement work:

Voulme expansion conducts work(gas piston)

$\delta W = -p \cdot A \cdot dx = -p \cdot dV$

Integration over whole displacement:

$W_{1,2,V} = - \int_{1}^{2} p\ dV$

Sign convetion from the perspective "inside" the system, means if the system gains energy => negative sign of work

Heat and heat Flow

-Heat is the other part of energy transported over system boundarys -Heat is transported due to temperature differences

Heat $Q$:

-can alter the system state -adiabatic: no heat is transferd

Heat Flow Q:

$\dot{Q} = \frac{dQ}{dt}$