Thermodynamics Flashcards
equation of state
describes the relationship between a systems thermodynamic properties
fundamental equation
combines the first and second laws of thermodynamics
dU=TdS=pdV+udN (Eulers eqn)
zeroth law of thermodynamics
if A, B, and C are thermodynamic systems such that A is in thermal equilibrium with B and B with C, then A is in equilibrium with C
first law of thermodynamics
dU=dQ-dW, where U is internal energy, Q is heat flow, and W is work done by the system
second law of thermodynamics
the entropy of an isolated system never decreases
third law of thermodynamics
at absolute zero temperature, entropy is zero for a crystalline structure
thermal EOS
T1=(dE1/dS1)=(dE2/dS2)=T2
mechanical EOS
-P1=(dE1/dV1)=(dE2/dV2)=-P2
chemical EOS
u1=(dE1/dN1)=(dE2/dN2)=u2
Gibbs-Duhem equation
SdT-VdP+NdU=0
you can derive this by expanding the fundamental equation!
dE=TdS+SdT-PdV-VdP+UdN+NdU
entropic form of the fundamental equation
S=E/T+PV/T-UN/T
ideal gas law
PV=NRT
how do you find the composition of an alloy at a given temperature?
draw a horizontal isothermal tie line intersecting the two adjacent solubility curves. drawing a vertical line down from the intersection of the tie line with the solubility curve gives you the amount of B in each constituent.
how do we calculate how compositions change as a function of temperature?
draw horizontal tie lines at each isotherm and find how much of B is in each phase at each temperature. to find the fraction of A, use the lever rule. f_A= (C_0-C_liq)/(C_A-C_liq)
eutectic system
a homogenous mixture that has a melting point lower than those of the constituents
