Solid States Flashcards
Molecules aggregate in different ways and have different phases (g,l,s). TRUE or FALSE
TRUE
Name 3 differences between gas, liquids and solids
1) Diff intermolecular distances
2) Diff molecular orientations
3) Diff energy levels
Gas and liquid display ‘no packing order’. TRUE or FALSE
TRUE
Solids displays ‘highly ordered packing’. TRUE or FALSE
TRUE
Does intermolecular distance increase or decrease from Gas…Liquid…Solid ?
Decrease
Does molecular orientation/mobility increase or decrease from Gas…Liquid…Solid ?
Decrease
Does potential energy increase or decrease from Gas…Liquid…Solid ?
Decrease
Name 9 physiochemical properties that impact solid state
1) Solubility
2) Dissolution rate
3) Bioavailability
4) Stability (Physical and chemical)
5) Melting point
6) Surface activity
7) Density
8) Electrostatic, Mechanical and Optical properties
9) Formulation design
State the 2 types of Solids
Amorphous (non-crystalline) and Crystalline
State the 3 classes of Crystalline solids
1) Polymorphs
2) Co-crystals
3) Hydrates and Solvates
Define ‘Crystalline state’
Molecules arranged in orderly, defined manner. W/same repeating units
Crystalline solids have HIGHER potential energy than amorphous state. TRUE or FALSE
FALSE. They have lower potential energy
Define ‘Polymorphism’
Repeating units arranged differently within the crystalline form (of the same substance)
Diff crystalline forms of the same substance have different MP’s. TRUE or FALSE
FALSE
State 3 methods of crystallisation
1) Supersatured solution
2) Cooling a molten sample before it’s melting point (e.g:suppositories, Creams and gels)
3) Precipitation of solids in solutions
due to -evaporation of liquid, addition of anti-solvent, after solubility of sample is changed by temp, pH and pressure of the system)
Describe the Crystallisation process
1) Nucleation
- First step in crystal formation
- A small mass of solute molecules cluster together and form a ‘nuclei’ -on which a crystal can grow
2) Growth
- The continued growth of the nuclei
To achieve Nucleation and growth, the solution must be supersaturated. TRUE or FALSE
TRUE
Polymorphism describes a crystalline solid sate that possess different … ?
- Crystalline forms
- Packaging pattern
- Lattice energies
- Properties
State 2 properties of ‘Stable form’ polymorphism
1) High MP
2) Slow dissolution rate
State 3 properties of ‘Metastable form’ polymorphism
1) Lower MP
2) Faster dissolution
3) Increase in apparent solubility
The conversion of metastable to stable form can be fast or slow depending on 2 things. What are they ?
1) Energy difference of both forms
2) Environmental conditions
Define ‘Monotropic polymorphism’
Only one stable polymorphic form (metastable will convert into stable over time)
Define ‘Enantropic polymorphism’
Material is transferred b/wn alternative stable forms. Less common
Describe the difference in solvent between Hydrate and Solvate
Hydrate; Solvent = Water
Solvate; Any solvent besides water e.g: Organic solvents -ethanol
‘Pseudopolymorphism’
Term used to describe the difference b/wn hydrates and anhydrous form
What is the slow dissolution rate of hydrates due to ?
Water strengthens the lattice e.g: Theophylline
What is the fast dissolution rate of hydrates due to ?
Water weakens the lattice e.g: Erythromycin
Why are solids amorphous ?
1) Insufficient solidification time for molecules to form order
2) Lack of kinetic energy therefore can’t overcome barrier b/wn crystal-liquid interface
3) Crystalline process has been broken through processing
State 5 properties of Solid Amorphous state
1) Less packing efficiency (less ordered)
2) Greater intermolecular distance
3) Greater molecular mobility
as a result of - stronger chemical reactivity and faster chemical degradation rate
4) Greater potential energy
5) Often higher solubility
-posses potential to enhance solubility and bioavailabilty of a poor water soluble drug
Low MW materials are usually Amorphous. TRUE or FALSE
TRUE
Larger MW compounds (e.g: Polymers) exhibit both ordered and disordered region aka Semi crystalline. TRUE or FALSE
TRUE
What is Tg ?
Glass Transition temperature
Define ‘Plasticiser’ and give a example of a plasticiser
A substance that is added to reduce Tg of an amorphous material. e.g: Water
At —- humidity, amorphous material absorb water (and may become crystalline). Fill in the gap
high
Water increases the molecular mobility of Amorphous materials. TRUE or FALSE
TRUE. Increased molecular mobility results in ordered alignment of molecules
What does ‘Crystal habit’ describe ?
The external shape of a crystal
Give examples of drug properties crystal habit has an effect on
- Dissolution rate
- Powder flow
- Stability (sedimentation rate and caking of suspension)
