What is the definition of the surface energy via the Gibbs enthalphy?
What is the definition of surface energy?
The energy required to increase the surface of a solid.
What is the difference between surface tension and surface energy?
Surface tension is mainly used for liquids
Surface energy is mainly used for solids
What is the definition of surface tension?
The force acting at the surface of a liquid that tends to minimize the area.
How is the singular binding energy of one bond calculated within a solid?
∆Hs is the enthalphy of sublimation (=bond breaking)
Z is the coordination number (=number of closest atoms)
Na is the avogadro constant
How can the surface energy be calculated for a fcc lattice in the {111} plane?
N/A = atoms per area
What is the radious of a flat surface?
infinity
What is the meaning of a moving surface that stays flat?
The chemical potential of both components is the same.
How is the chemical potential relation for a surface with curvature?
Specify that for a spherical surface.
spherical surface:
How is the surface energy and the vapour pressure related?
With P being the vapour pressure at r=r or r=infinity
How is the solubility and the surface energy related?
What qualitative statement can one make on the influence of particale size on the surface energy.
The surface energy in smaller particles is greater than in big ones, which makes particle growth likely.
What general statement can be made about the particle sizes infleunce on solubility.
Name two ways to measure the surface energy of liquids.
Injecting an inert gas into a liquid with a capillary tube
measurement over the maximum pressure in half sphere sphere state
Rise of liquid inside the capillary tube
measurement via angle towards glass
How si the surface energy measured in solids?
Wires are heated to 0,9Tm with applied weight. The gravity works to elongate the wire the surface energy works to shorten the wire.
r is the wire radius and m the applied mass
Which contact angles stand for which intensity in wetting?
If θ ~ 0° superhydrophilicity
If θ < 90° the liquid is said to wet the solid
If θ > 90° the liquid is said non wetting
If θ = 180° the liquid is non wetting at all.
What is the internal energy balance for the interface between two liquids?
What is the surface excess?
Surface excess in thermodynamics represents the difference in concentration of a substance at the surface compared to its concentration in the bulk phase.
ni is the number of moles at the interface
<0:depletion at surface
>0:increase at surface
How does the particle size change the melting temperature?
How can the Surface energy be calculated from the surface excess.
What is the Gibbs adsorption theorem?
How can adsorption on surfaces be described mathematically?
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