Surface Science

Question 1

surface energy

Answer 1

higher Gibbs free energy thank bulk making it more reactive

Question 2

work done to create surface

Answer 2

relaxation = small changes in bond lengths/angles at surface
reconstruction = substantial changes in surface

Question 3

hard to determine surface structure because

Answer 3

need surface sensitive techniques as absolute number of atoms/molecules is small
need surface selective techniques as there’s always a large amount of bulk material
surface specific = method interacts with surface only

Question 4

minimising Gibbs free energy of the surface

Answer 4

curvature, sphere has a lower SA and therefore a lower Gibbs free energy, if Pext increases the volume decreases and the Pint increases to compensate, can then calculate dG = free energy change due to change in vol of bubble

Question 5

capillaries

Answer 5

narrow, large diff between Pext and Pin, liquid rises in capillary due to hydrostatic pressure

Question 6

surface wetting

Answer 6

contact angle between substrate and surface > 90, forces stronger between molecules in liquid than between liquid and solid so no wetting
and vice versa

Question 7

contact angle

Answer 7

balance of angles between surface-gas, surface-ligand and liquid-gas interphases

Question 8

sticking coefficient

Answer 8

no of molecules stuck / no of incident molecules

Question 9

sticking coefficient dependent on

Answer 9

surface temp as desorption increases with increasing T, no of atoms/molecules already stuck to the surface, translational and internal energies of incident molecule