Colloids Flashcards
(26 cards)
A substance microscopically dispersed throughout another substance.
Colloid
What can colloid particles pass through?
Filter paper but not through a semipermeable membrane.
What are the two phases of a colloidal system?
- Dispersed phase (A discontinuous phase)
- Dispersion medium (A continuous phase)
What are the characteristics of dispersed-phase particles?
The dispersed-phase particles have a diameter of between approximately 1 nm - 1000nm. Such particles are normally invisible in an optical, though their presence can be confirmed with the use of an ultramicroscope or an electron microscope.
What is a solution made up of?
Particles or solutes and a solvent. The solvent part of the solution is usually a liquid, but can be a gas. The particles are atoms, ions, or molecules that are very small in diameter.
What are the characteristics of a colloidal mixture?
Has particles that are not as small as a solution and not as large as a suspension. The particles are intermediate in size.
What are suspensions made up of?
Particles and a solvent. The dispersed phase particles are larger than those found in the dispersion medium.
Has particles that are not as small as a solution and not as large as a suspension.
The particles are intermediate in size.
Colloidal Mixture
Made up of particles and a solvent
its particles are larger than those found in a solution.
The particles in a suspension can be distributed throughout the suspension evenly by shaking the mixture.
Suspension
has a great affinity for the dispersion medium.
They are also termed as intrinsic colloids.
If the dispersion medium is water, they are called hydrophilic or emulsoids.
generally self- stabilized.
Reversible in nature and are heavily hydrated, examples are starch, gelatin, rubber, protein etc.
Lyophilic Colloids
These are also referred as extrinsic colloids
They are irreversible by nature and are stabilized by adding small amount of electrolyte.
If the dispersion medium is water, the lyophobic colloids are called hyrophobic or suspenoids.
Examples: sols of metals like Au, Ag, sols of metal hyroxides and sols of metal sulphides.
poorly hydrated.
Lyophobic Colloids
These colloids behave as normal electrolytes at low concentrations but behave as colloids at higher concentrations.
are also referred to as micelles.
Associated Colloids
The continuous zigzag movement of the colloidal particles in the dispersion medium in a colloidal solution is called Brownian movement.
Brownian Movement
The continuous zigzag movement of the colloidal particles in the dispersion medium in a colloidal solution is called?
Brownian Movement
is due to the unequal bombardments of the moving molecules of dispersion medium on colloidal particles.
decreases with an increase in the size of colloidal particles. This is why suspensions do not exhibit this type of movement.
Brownian Movement
As a result of Brownian motion particles pass (diffuse) from a region of higher concentration to one with lower conc.
Diffusion
At small particle size (less than 0.5 um) Brownian motion is significant & tend to prevent sedimentation due to gravity & promote mixing in stead.
Sedimentation
The resistance to flow of a system under an applied pressure.
Viscosity
The resistance to flow of a system under an applied pressure.
Viscosity
are of relatively low viscosity.
Spherocolloidal Dispersions
dispersions are of high viscosity.
Linear Colloidal Dispersions
Is due to the scattering of light by colloidal particles.
can be used to distinguish a colloidal solution from a true solution. The phenomenon has also been used to devise an instrument known as ultra microscope. The instrument is used for the detection of the particles of colloidal dimensions.
Tyndall Effect
Particles appear as spots of light against the dark background of the microscope.
Used in the technique of micro electrophoresis for measuring particle charge.
Ultra Microscope
Give actual picture of the particles (up to 5A).
Used to observe the size, shape and structure of sols.
High energy electron beams are used. (have greater resolving power)
One disadvantage is; only DRIED samples can be examined. Not give information on solvation.
Electron Microscope
