The lattice fluid model in the grand canonical ensemble is presented as a useful system for teaching liquid-vapor coexistence and the PVT surface of a fluid. The state of the fluid in the grand canonical ensemble is specified by the temperature T, the volume V, and the chemical potential μ. The p̂(T,V,μ) and v(T,V,μ) equations of state of the lattice fluid, where v is the volume per particle, are derived from the grand canonical partition function in the mean-field approximation. We distinguish between the integral pressure p̂Ω/V and the differential pressure p(Ω/V)T,μ, where Ω is the Landau potential so that we can discuss finite size effects near first-order phase transitions. The nonequivalence of the canonical and grand canonical ensembles for describing the liquid-vapor phase transition is also discussed.

1.
T.
Andrews
, “
The Bakerian lecture: On the continuity of the gaseous and liquid states of matter
,”
Philos. Trans. R. Soc. London
159
,
575
590
(
1869
).
2.
J. D.
van der Waals
, “
The equation of state for gases and liquids
,” Nobel Lecture,
1910
, ⟨nobelprize.org/nobel_prizes/physics/laureates/1910/waals-lecture.pdf⟩.
3.
J. S.
Rowlinson
,
Liquids and Liquid Mixtures
(
Butterworths
,
London
,
1969
), p.
66
.
4.
L. M.
Quintales
,
J. M.
Alvariño
, and
S.
Velasco
, “
Computational derivation of coexistence curves for van-der-Waals-type equations
,”
Eur. J. Phys.
9
,
55
60
(
1988
).
5.
D.
Chowdhury
and
D.
Stauffer
,
Principles of Equilibrium Statistical Mechanics
(
Wiley-VCH
,
Weinheim
,
2000
).
6.
J.
Tobochnik
, “
Critical point phenomena and phase transitions
,”
Am. J. Phys.
69
,
255
263
(
2001
).
7.
J. L.
Barrat
and
J. P.
Hansen
,
Basic Concepts for Simple and Complex Liquids
(
Cambridge U. P.
,
Cambridge
,
2003
).
8.
B.
Widom
, “
Intermolecular forces and the nature of the liquid state
,”
Science
157
,
375
382
(
1967
).
9.
T. D.
Lee
and
C. N.
Yang
, “
Statistical theory of equations of state and phase transitions. II. Lattice gas and Ising model
,”
Phys. Rev.
87
,
410
419
(
1952
).
10.
P. T.
Landsberg
,
Problems in Thermodynamics and Statistical Physics
(
Pion
,
London
,
1971
), p.
252
.
11.
J.
Tobochnik
,
H.
Gould
, and
J.
Machta
, “
Understanding temperature and chemical potential using computer simulations
,”
Am. J. Phys.
73
,
708
716
(
2005
);
M. P.
Tarazona
and
E.
Saiz
, “
Understanding chemical potential
,”
J. Chem. Educ.
72
,
882
883
(
1995
).
12.
T. L.
Hill
,
Thermodynamics of Small Systems
(
Dover
,
New York
,
1994
).
13.
V.
García-Morales
,
J.
Cervera
, and
J. A.
Manzanares
, in
Handbook of Nanophysics: Principles and Methods
, edited by
K. D.
Sattler
(
CRC
,
Boca Raton
,
2010
), Chap. 15.
14.
G.
Gallavotti
,
Statistical Mechanics: A Short Treatise
(
Springer
,
Berlin
,
1999
), Chap. 5, p.
176
.
15.
T. L.
Hill
,
Statistical Mechanics
(
McGraw-Hill
,
New York
,
1956
), Appendix 9.
16.
I. J.
McNaught
, “
Spreadsheet calculation of vapor pressures and coexistence curves
,”
J. Chem. Educ.
70
,
232
234
(
1993
).
17.
R.
Fowler
and
E. A.
Guggenheim
,
Statistical Thermodynamics
(
Cambridge U. P.
,
Cambridge
,
1949
), p.
431
.
18.
J.
Stephenson
, “
Fluctuations in the number of particles in a grand canonical ensemble of small systems
,”
Am. J. Phys.
42
,
478
481
(
1974
).
19.
L.
Tisza
,
Generalized Thermodynamics
(
MIT Press
,
Cambridge, MA
,
1966
), p.
39
.
20.
K.
Huang
,
Introduction to Statistical Physics
(
Taylor & Francis
,
London
,
2001
), p.
4
.
21.
H. M.
Schaink
and
P.
Venema
, “
The van der Waals equation of state and the law of corresponding states: A spreadsheet experiment
,”
J. Chem. Educ.
84
,
2030
2030
(
2007
).
22.
J. A.
Coch Frugoni
,
M.
Zepka
,
A.
Rocha
, and
M.
Coretti
, “
A simple and economic three dimensional model for the PVT surface of water
,”
J. Chem. Educ.
61
,
1048
1048
(
1984
).
23.
B. W.
Jones
, “
Determination of the PVT surface of a freon
,”
Phys. Educ.
10
,
498
499
(
1975
).
24.
A.
Sommerfeld
,
Thermodynamics and Statistical Mechanics
(
Academic
,
San Diego
,
1964
), p.
65
.
25.
N. B.
Wilding
, “
Computer simulation of fluid phase transitions
,”
Am. J. Phys.
69
,
1147
1155
(
2001
).
26.
J.
Güémez
and
S.
Velasco
, “
The probability distribution for a lattice gas: A simple characterization of the liquid-vapor phase transition
,”
Am. J. Phys.
59
,
335
340
(
1991
).
27.
A. V.
Neimark
and
A.
Vishnyakov
, “
Phase transitions and criticality in small systems: Vapor-liquid transition in nanoscale spherical cavities
,”
J. Phys. Chem. B
110
,
9403
9412
(
2006
).
28.
S. M.
Oversteegen
,
P. A.
Barneveld
,
F. A. M.
Leermakers
, and
J.
Lyklema
, “
On the pressure in mean-field lattice models
,”
Langmuir
15
,
8609
8617
(
1999
).
29.
J.
Pellicer
,
J. A.
Manzanares
, and
S.
Mafé
, “
Ideal systems in classical thermodynamics
,”
Eur. J. Phys.
18
,
269
273
(
1997
).
30.
J. M.
Pimbley
, “
Volume exclusion correction to the ideal gas with a lattice gas model
,”
Am. J. Phys.
54
,
54
57
(
1986
).
31.
F.
Schwabl
,
Statistical Mechanics
(
Springer
,
Berlin
,
2006
), p.
408
.
AAPT members receive access to the American Journal of Physics and The Physics Teacher as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.