disperse systems - dosage forms

Question 1

What is a colloid?

Answer 1

• two phase system of matter
• a mixture intermediate between heterogenous and homogenous

Question 2

What Is a phase colloid?

Answer 2

small droplets or particles of one substance (the disperse
phase) are dispersed in another (the continuous phase)

Question 3

What is a molecular colloid?

Answer 3

macromolecules are dispersed in a continuous phase

Question 4

What are properties of colloids?

Answer 4

*tyndall effect (scatter light)
*molecules of liquid in motion under microscope (Brownian motion)
* Adsorbtion
* Dialysis
* Electrophoresis (charged ions)
* Thixotropy (viscosity change with force) thick → thin

Question 5

What are properties of solutions?

Answer 5

• Dissolving a solute into a solvent
• Molecular dispersion
• Contain small particles (ions or molecules)
• Transparent
• Do not separate
• Cannot be filtered
• Do not scatter light

Question 6

What are the types of colloids? (liquid continuous phase)

Answer 6

• gas + liquid → foam
• liquid + liquid → emulsion
• solid + liquid → sol, suspension

Question 7

What are the types of colloids (gas continuous)?

Answer 7

• liquid + gas → liquid aerosol
• solid + gas → solid aerosol

Question 8

What are the types of colloids (solid continuous)?

Answer 8

• gas + solid → solid foam
• liquid + solid → solid emulsion
• solid + solid → solid suspension

Question 9

What is lyophobic? (two phase)

Answer 9

solvent hating - hydrophobic when solvent is water

Question 10

What is lyophilic? (one phase)

Answer 10

solvent loving - hydrophilic when solvent is water

Question 11

What are properties of lyophobes?

Answer 11

Inorganic molecules or particles (insoluble)
Little or no interaction
between particles and dispersion medium
Do not disperse spontaneously,
special procedures needed
No effect on viscosity unsolvated
Electrolytes: low concentrations may stabilise,
higher concentration causes instability

Question 12

What are the properties of lyophiles?

Answer 12

Large organic molecules in colloidal size range
Solvated by medium (H2O – this is hydrated)
Disperse spontaneously
increase viscosity, forming gels at higher
concentrations
Electrolytes: generally stable but “salted out” by very
high concentrations due to desolvation

Question 13

What is a gel?

Answer 13

a colloidal suspension in which the liquid medium has become
viscous enough to behave more or less as a solid

Question 14

What is the appearance of a solid?

Answer 14

clear, transparent, homogenous

Question 15

What is the appearance of a colloid?

Answer 15

Cloudy, but uniform and homogenous

Question 16

What is the appearance of a suspension?

Answer 16

Cloudy, heterogenous and at least two substances visible

Question 17

Is there separation in any of the following?

Answer 17

Solution: None
Colloid: none
Suspension: particles will eventually settle out

Question 18

How do the following filter?

Answer 18

Solution: passes through filter
Colloid: passes through filter
Suspension: particles filtered out

Question 19

what is the effect of light on the following?

Answer 19

Solutions: None
Colloid: scatters light
Suspension: variable - generally can not pass through

Question 20

What is the visibility of the following like?

Answer 20

Solutions: particles not visible under the microscope
Colloid: particles visible under microscope
Suspension: particles visible to naked eye