Principles of the solid state Flashcards
Solids are highly ordered packing. TRUE OR FALSE?
TRUE
Gases and liquid have no packing order. TRUE OR FALSE?
TRUE
Name some of the physicichemical properties that impact the solid state?
- Solubility
- Dissolution rate
- Melting point
- Bioavailability
- Surface activity
- Density
- Stability
What two states can a solid be in?
- Amorphous
- Crystalline
Name the different types of crystalline?
- Polymorphs
- Co-crystals
- Solvates, Hydrates
Describe the properties of the crystalline state
- Molecules are arranged in orderly defined manner with same repeating units
- Lower potential energy than amorphous state
- Repeating units can be arranged differently within the crystalline form of the same substance
- Different crystalline forms of the same substance posses different melting points/temp at which ordered lattice breaks down)
What are the methods for crystallisation?
- Supersaturated solution
- Crystallisation through cooling molten sample below its melting point
- Precipitation of solids in solutions
Provide examples for Crystallisation through cooling molten sample below its melting point
- Suppositories
- Creams
- Gels
Provide examples for precipitation of solids in solutions
- Evaporation
- Addition of anti-solvent
- After solubility of samples changed by temp/pressure/ph of the system
Name and describe the different steps involved in the crystallisation process?
-Nucleation : First step of forming crystals
/a small mass (solute molecules) cluster together to form a nuclei on which a crystal can grow
-Growth : The continued growth of the nuclei
In order to achieve nuleation and growth the solution must not be supersaturated. TRUE OR FALSE?
FALSE
What is polymorphism?
- When a crystalline state solid possesses
- different crystalline forms
- Different packing pattern
- Different lattice energies
- Different properties
Polymorphism can present in a stable and metastable form. TRUE OR FALSE?
TRUE
Describe both stable and metastable form of polymorphism
Stable form - Higher MP, slower dissolution rate
Metastable form - Lower MP, faster dissolution, increase in apparent solubility
Metastable form will transform into most stable form. TRUE OR FALSE?
TRUE
What is monotropic polymorphism?
-Only one stable polymorphic form (metastable will transform into stable over time)
What is enantropic polymorphism?
-Material reversibly transformed between alternative stable forms.
Which one is less common, monotropic or enantropic polymorphism?
Enantropic
During crystallisation the solvent molecules can be trapped in the crystal lattice. TRUE OR FALSE?
TRUE
What is monohydride and dihydride?
- Monohydride: 1 molecule of water:Molecule substance
- Dihydride: 2 molecules of water: 1 Molecule substance
What is a solvate?
-Another solvent instead of water e.g organic solvents such as ethanol
What is pseudopolymorphism?
-Used to describe the different between hydrates and anhydrous forms
The hydrate form can have a slower or faster dissolution. TRUE OR FALSE?
TRUE
Describe the properties of amorphous state?
- lower packing efficiency (less ordered)
- Greater intemolecular distance
- Greater molecular mobility
- Greater potential energy
- Often higher solubility
Why are solids amorphous?
- Insufficient solidification time for molecules to form order
- Lack of kinetic energy to overcome barrier between crystal-liquid interface
- The crystalline process has been broken through processing
Low MW materials are commonly amorphous. TRUE OR FALSE?
TRUE
Larger MW compounds such as polymers disordered exhibit both ordered and disordered region - semi crystalline. TRUE OR FALSE?
TRUE
Degree of crystallinity results in different properties. TRUE OR FALSE?
TRUE
Amorphous forms have a characteristic temp at which there is a major change in properties, known as the GLASS TRANSITION TEMPEARTURE (Tg). TRUE OR FALSE?
TRUE
What occurs when Tg is greater?
- Glassy brittle state
- Lower mobility of molecules
What occurs when Tg is less than?
- Rubbery
- Higher mobility of molecules
What are plasticisers and provide an example of a good plasticiser?
- Substances added to reduce Tg of an amorphous material
e. g Water
At relatively high humdity’s amorphous materials do not absorb water. TRUE OR FALSE?
FALSE
Plasticising material with water leads to the reverting to the crystalline state leading to weight loss. TRUE OR FALSE?
TRUE
What is crystal habit?
- Eternal shape of the crystal due to rate of crystal gowth at different faces influenced by crystalline conditions.
Crystal habit can be different for different internal packing but also different for the same packing. TRUE OR FALSE?
TRUE
Crystal habit affects drug properties, such as dissolution rate, powder flow and stability. TRUE OR FALSE?
TRUE
