Thermodynamics of surfaces and interfaces Atkins (ed. 10 and 11): §16C.2 - 16C.4 Atkins (ed. 9): §17.8 - 17.10 Atkins (ed. 8): §18.7 - 18.8 Study Guide: P.14

Na2ClO3 crystals in solution

Large crystals grow; small crystals dissolve T = 1 day 3

Large crystals grow; small crystals dissolve Wilhelm Ostwald Ostwald ripening (1896) T = 0 T = 1 day 4

Equilibrium: one single crystal T = 1 day 10 days 30 days 5

Equilibrium: one single crystal T = 1 day 10 days 30 days 6

Gibbs-Thomson effect Interfacial (free) energy between two phases

Gibbs-Thomson effect Interfacial (free) energy between two phases relevant for P >1 P =1 P =2,3 P =2,3

Laplace equation: γ surface free energy (Jm-2) out in Equilibrium:

Laplace equation γ r γ r+dr equilibrium Laplace equation

Surface tension γ (Jm-2 = Nm-1) water

Surface tension and capillary action Pressure of liquid column of height h Laplace equation equilibrium capillary action Adhesive force between fluid and capillary

Surface tension and capillary action γ counteracts the adhesion between liquid or gas and capillary

Surface tension and wetting specific work (J/m2) of adhesion (γ is always trying to reduce the corresponding surface) horizontal Force (N/m) balance (equilibrium)

Surface tension and wetting } Work (J/m2) Force (N/m) partial dewetting partial wetting

Kelvin equation (nucleation barrier for condensation (g  l)) γ Pout Laplace equation Pin l g equilibrium constant T Kelvin equation small droplets evaporate condensation nucleation barrier  Pg > P*

nucleation of phase α(l) from phase β(s) revert to Gibbs free energy classical nucleation theory spherical nucleus, radius r driving force: surface free energy: γ molar volume: Vm γ β α Free energy gain cost

nucleation barrier depends on supersaturation nucleation barrier and critical radius Δμ Δμ Δμ Δμ Δμ nucleation barrier depends on supersaturation (Δμ = Δμ(T)) -low Δμ : no nucleation -high Δμ : easy nucleation