Colloids Flashcards
Define dispersed system
a system in which one substance is distributed as particles throughout another phase
What are the two parts of a dispersed system?
disperse phase
dispersion medium
Define molecular dispersions
also known as true dispersions
solute molecules are homogeneously distributed throughout the solvent
List some examples of dispersed system
colloid
gels
suspensions
emulsion
lotion, ointments and cream
Which physicochemical feature is most important to define the type of the dispersed system?
size of the dispersed particles
What the types of dispersed systems based on?
the physicochemical properties of the dispersed particles and dispersion medium
What are the two classifications?
colloidal dispersions
coarse dispersions (suspensions)
What is the particle size of colloids?
1-500 nm
What is the common use for colloidal systems?
excellent candidate for research regarding novel nano-drug delivery systems
List some unique properties of colloids
Platinum is effective as a catalyst only as platinum black (colloidal form)
Cellular uptake of nanoparticles is different from micro/macroparticles or true molecular dispersions – drug delivery, toxicity
What are some shapes that colloidal systems have?
may can occur as
globules
rods
flakes
threads
branched structure
What factors does shape and size define?
flow
sedimentation
osmotic pressure
Distinguish between solutions as related to particle size and dispersion.
Particle size: < 1 nm
Dispersion: Homogeneous (particles uniformly distributed throughout the mixture)
Examples: Saltwater, sugar water, air
Distinguish between colloids as related to particle size and dispersion.
Particle size: 1-500 nm
Dispersion: Heterogeneous (particles are not uniformly distributed and may settle over time)
Examples: Milk, fog, gelatin
Distinguish between suspensions as related to particle size and dispersion.
Particle size: > 1000 nm
Dispersion: Heterogeneous (particles settle quickly and can be filtered out)
Examples: Muddy water, blood, sand in water
Give examples of colloids in various states of matter
Gas: Smoke, fog, aerosol sprays
Liquid: Milk, blood, ink
Solid: Pearl, opal, cheese
List the key features of lyophilic colloids
Also known as hydrophilic colloids
Can be easily dispersed in a solvent
Have a strong attraction to the solvent molecules
Examples: Starch, proteins, cellulose
List the key features of lyophobic colloids
Also known as hydrophobic colloids
Have little to no affinity for the solvent molecules
Cannot be easily dispersed in a solvent
Require the addition of a stabilizing agent to remain dispersed
Examples: Gold, silver, sulfur
Define gels and give examples
A type of colloid where a solid network is formed throughout a liquid
The solid component is referred to as the gel network or gel phase
Examples: Jell-O, hair gel, toothpaste
Define Magmas/Milks and give examples
A type of colloid where a solid is suspended in a liquid
The solid particles are larger than those in a solution but smaller than those in a suspension
Examples: Concrete, lava, paint
What are colloidal dispersions and how do they differ from coarse dispersions (suspensions)?
Colloidal dispersions are systems in which the particle size ranges from 1-500nm and the particles are too small to see with the naked eye. They have a large surface area and unique properties, and may occur as globules, rods, flakes, threads or branched structures. Coarse dispersions (suspensions), on the other hand, have larger particle sizes and are visible to the naked eye.
What are some examples of colloids in various states of matter?
The components of a colloidal dispersion may be in any of the three states of matter (solid, liquid or gas). Of the 9 possibilities, 8 exist as colloidal dispersions. For example, milk is a colloidal dispersion of fat particles in water (a liquid-liquid colloidal system), while smoke is a colloidal dispersion of solid particles in air (a solid-gas colloidal system).
List some unique properties of colloids
Platinum is effective as a catalyst only as platinum black (colloidal form)
Cellular uptake of nanoparticles is different from micro/macro particles or true molecular dispersions – drug delivery, toxicity
Describe lyophobic colloids
Lyophobic colloids are colloidal dispersions in which the dispersed phase is not attracted to the dispersion medium. This means that the particles of the dispersed phase tend to repel each other and may require the addition of a stabilizing agent in order to prevent them from aggregating or settling out of the dispersion. Some examples of lyophobic colloids include suspensions of metal oxides in water and emulsions of oil in water.
