Studied by 6 people0th Law of Thermodynamics
if two thermodynamic systems each are in thermal equilibrium with a third, then they are in thermal equilibrium with each other
temperature
a property that determines the direction of heat flow when an object is in contact with another object
internal energy (U)
kinetic energy + potential energy
ideal gases
have no interactions between particles; the internal energy is only a function of temperature and not a function of pressure or volume
variables of state
depend on the state of the system and not how the system arrived at that state
variables of state examples
pressure, volume, temperature, internal energy
work (w)
ordered kinetic energy, no entropy component, high quality
heat (q)
disordered kinetic energy, entropy component, low quality
transfer of internal energy
delta U = q + w
exothermic process
q < 0; heat leaves the system
endothermic process
q > 0; heat enters the system
1st Law of Thermodynamics
energy is conserved; the total energy of the system and the surroundings is constant
isothermal
constant temperature (delta T = 0)
isochoric
constant volume (deltaV = 0, w = 0)
isobaric
constant pressure (deltaP = 0)
adiabatic
no heat is transferred (q = 0)
cyclic
no change in state variables (final state = initial state)
intensive variables of state
independent of the amount of material (eg. pressure, temperature, specific and molar heat capacity, density)
extensive variables of state
proportional to the amount of material (eg. volume, mass, internal energy, entropy, heat capacity)
isothermal expansion of ideal gases
qT OR wT
Cv
heat capacity at a constant volume
Cv of a monoatomic gas
3/2R
Cv of a diatomic gas (small)
5/2R
Cv of a diatomic gas (large)
7/2R
Cv of a linear polyatomic gas
5/2R
Cv of a non-linear polyatomic gas
3R
isobaric expansion of ideal gases
qP OR wP
liquid/solid energy and enthalpy
deltaU approx. equal to deltaH; Cp
standard enthalpy per mole
the enthalpy of formation of 1 mol of the compound at 1 bar pressure from its elements in their standard states
adiabatic reversible expansion
use Cvln(T2/T1) = -Rln(V2/V1)
real gas law A term
accounts for attractive forces between molecules
real gas law B term
accounts for the intrinsic volume of gas molecules
Joule-Thomson Experiment
measuring the temperature of a gas (T1, T2) before and after it expands from P1 to P2 through a porous plug
Joule-Thomson coefficient for ideal gases
0
Joule-Thomson coefficient for real gases
depends on changes in internal energy during expansion caused by intermolecular interactions
Carnot Cycle 1 to 2
isothermal reversible expansion; top left-right curve
Carnot Cycle 2 to 3
adiabatic reversible expansion; right up-down curve
Carnot Cycle 3 to 4
isothermal reversible compression; bottom right-left curve
Carnot Cycle 4 to 1
adiabatic reversible compression; left down-up curve
efficiency
1 - (Tcold/Thot)
Note
Flashcard