Interfaces Flashcards
5 types of interface?
Solid/solid , solid/liquid , solid/gas , liquid/gas , liquid/liquid
Surface energy?
Energy needed to create a new surface by breaking bonds in substance
What is surface energy proportional to?
Strength of bonding between atoms and molecules
Surface tension?
Is the surface energy of a liquid.
Due to water molecules at surface receiving uneven attraction, they tend to be drawn to centre of liquid. Is in a state of tension that minimises it’s surface area
Inward pull of drop?
Surface tension
How do water droplets form on grease?
Water has a higher surface energy than greasy surface.
Droplet shape is caused by?
Higher surface tension of liquid = more spherical shape of droplet
What is wetting?
Contact between solid and liquid.
Depends on contact angle between droplet and surface.
Ability to wet depends on?
The attraction of liquid particles to bulk of liquid
AND
The attraction of liquid particles to surface of solid
Particles are strongly attracted toward centre of liquid in than solid in terms of wetting?
Liquid doesn’t wet, and a droplet forms
Particles in liquid are strongly attracted to solid surface than centre in terms of wetting?
Liquid spreads out across solid surface and wets
How will wetting occur?
If surface energy of solid is greater than surface tension of water
What are surfactants?
Surface active agents. Eg, detergent
Detergent molecules reduce hydrogen binding between water molecules and surface tension is reduced.
What is meniscus?
The curved surface of water, can be concave (wetting occurs) or convex.
Concave meniscus?
Water has a lower surface energy than container, and will wet to the container producing a concave meniscus.
