colloids

Question 1

what is a colloid

Answer 1

a mixture of particles of the same component (meaning they have to be the same thing) with diameters of 10^-7 to 10^-9 (meaning they are larger than atoms but they are small enough to not be seen by the naked eye). suspended in a continue phase of another component

Question 2

what are the different types of colloids

Answer 2

sol
gels
foams
aerosols
emulsions

Question 3

what is a sol colloid

Answer 3

solids sistered in liquids

lyophilic - liquid loving colloids, they easily disperse and the free energy of mixing them is negative (so it doesn’t require energy for them to get together)
they are thermodynamically stable

lyophobic - thermodynamically unstable - large surface to volume
irreversible aggregation, tend to be insoluble, difficult to prepare- requires specialised methods
system is at a high energy state - cause it wants to change
eg. cabotegravir - treating hiv

association collioids - also known as aggregation colloids or micelles because they are amphiphilic

Question 4

what is gel colliod

Answer 4

liquids dispersed in solids

used for wound dressing, contact lenses and to grow bacteria

Question 5

what is foam colloids

Answer 5

gas dispersed in liquids

they can be used as drug delivery for example to the scalp for flakey skin conditions - they are easily spreadable (viscous)
the liquid content is so low so it dries quickly

Question 6

what is aerosol colloids

Answer 6

liquid/solid dispersed in gas

to spray
to access parts of the body that you can’t
cavity filing - asthma inhalers
formulation of aerosols can be very hard

Question 7

what is emulsions colloids

Answer 7

liquids dispersed in liquids

Question 8

what is the definition of a solution and why is it not a colloid

Answer 8

a mixture of two or more components that form a single phase which is homogenous, where the solute goes through dissolution
- this is when the solute dissolves in the solvent to form a solution

however if they do not undergo dissolution then they are in a DISPERSED SYSTEM, this is because they are heterogeneous (so they are not all in the same state)
if it is stable it Is a colloid.

Question 9

what can go wrong with colloids

Answer 9

• contamination
• chemical instability - impurities, by products,
• physical instability’s- where lyophobic sold will aggregate together
• storage limitations

Question 10

what does the polydispersity index value for colloids mean

Answer 10

if the value is 1 = then there is large variant ion in size

if the value is 0 = then there is no size variation

Question 11

what are the kinetic properties of colliod systems

Answer 11

• brownian motion and diffusion
• collioins of colliods with continuous phase
• this leads to random movement
• collioidal diffusion to areas of low concerntration

Question 12

what are the optical properties of colliods

Answer 12

• collioids absorb and scatter light
• light scattering makes the dispersion turbid/cloudy - this is called the tyndall effect
• degree of cloudiness depends on size and or the molecular average weight of particle

Question 13

what are the electrical properties of colloids

Answer 13

• surfaces become electrically charged in aqueous mediums due to

1. ion dissolution - unequal dissolution of oppositely charged ions
2. ionisation - native charge of ionised groups - such as weak acids or bass
   - ion dis

Question 14

what are the size and shape of colliods

Answer 14

• a decrease in size causes an increase in sa; v ratio
• collioids amy not like being in contact with water

many colliods are spherical
- several equations assume that they are spheres - this is a limitation

Question 15

what is the electrical double layer

Answer 15

• the way that acharged p;article interacts with ions in an aqueous solution