Capillarity and Surface Forces (Liquids) - Surface and Colloid Chemistry: Principles and Applications - page 32

table 2.1 ( Continued )
Surface tension values of Some common liquids

liquid Surface tension

Propanol 23.7

Pyridine 38.0

3-Pyridylcarbinol 47.6

Pyrrol 36.6

sym -Tetrabromoethane 49.7

tert -Butylchloride 19.6

sym -Tetrachloromethane 26.9

Tetrahydrofuran (THF) 26.4

Thiodiglycol 54.0

Toluene 28.4

Tricresylphosphate (TCP) 40.9

Water 72.8

o -Xylene 30.1

m -Xylene 28.9

a -Bromonaphthalene (BN) 44.4

a -Chloronaphthalene 41.8

Mercury 425.4

Metals (liquid state: high temperature) Greater than 1000

Note: Surface tension (20°C; mN/m [dyn/cm]).

The surface free energy, G S , per unit area is given as

G S = γ = (dG/d A ) T,P (2.42)

Hence, the other thermodynamic surface quantities will be
Surface entropy:

S S = −(dG S /dT) P (2.43)

= −(d γ/dT) (2.44)

We can thus derive for surface enthalpy H S

H S = G S + T S S (2.45)

All natural processes are dependent on the effect of temperature and pressure. For
instance, oil reservoirs are found under high temperatures (ca. 80°C) and pressure
(around 100 to 400 atm [depending on the depth]). Thus, one must investigate such
systems under these parameters. This is related to the fundamental equation for free
energy, G, enthalpy, H, and entropy, S, of the system: