Thermo Lecture 3 Flashcards
What is a spontaneous change?
It proceeds towards equilibrium with no outside intervention
What is an isolated system?
One where no expansion work on it’s surroundings is possible.
What is entropy?
A property that predicts the feasibility and direction of spontaneous change in an isolated system
What is the equation for entropy?
dS = dQrev/T
Qrev means no energy dissipation and the transformation takes place between equilibrium states
What is ΔS for an isolated system?
ΔSisolated = ΔQ[(T2-T1)/T1T2)]
Always greater than or equal to zero
ΔSsys + ΔSsurr = ?
Greater than or equal to 0
What is the 2nd Law of Thermodynamics?
The total entropy of the system and the surroundings can never decrease
- Express U in terms of state functions
2. Express H in terms of state functions
- dU = TdS - PdV
2. dH = TdS + VdP
Give the formula for Entropy, S, in terms of microstates. What does this imply?
S = R/N lnΩ
A high value of entropy corresponds to a greater number of equivalent microstates.
What is the thermodynamic efficiency and what is it’s equation?
The max rate of performing mechanical work.
η = 1 - T1/T2
What is the Carnot Cycle?
An ideal reversible closed thermodynamic cycle in which the working substance goes through the four successive operations of isothermal expansion, adiabatic expansion, isothermal compression, and adiabatic compression back to its initial state
What is the 3rd Law of Thermodynamics?
As T approaches 0 K, the heat capacity (and entropy) approaches 0
What is ‘Gibbs Paradox’?
entropy is additive so when a partition is removed between 2 gases the entropy increases. However if the gases are identical the removal of the partition cant increase entropy as the partition makes no difference to the system.
