Principles of the solid state

Question 1

Solids are highly ordered packing. TRUE OR FALSE?

Answer 1

TRUE

Question 2

Gases and liquid have no packing order. TRUE OR FALSE?

Answer 2

TRUE

Question 3

Name some of the physicichemical properties that impact the solid state?

Answer 3

• Solubility
• Dissolution rate
• Melting point
• Bioavailability
• Surface activity
• Density
• Stability

Question 4

What two states can a solid be in?

Answer 4

• Amorphous

- Crystalline

Question 5

Name the different types of crystalline?

Answer 5

• Polymorphs
• Co-crystals
• Solvates, Hydrates

Question 6

Describe the properties of the crystalline state

Answer 6

• 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)

Question 7

What are the methods for crystallisation?

Answer 7

• Supersaturated solution
• Crystallisation through cooling molten sample below its melting point
• Precipitation of solids in solutions

Question 8

Provide examples for Crystallisation through cooling molten sample below its melting point

Answer 8

• Suppositories
• Creams
• Gels

Question 9

Provide examples for precipitation of solids in solutions

Answer 9

• Evaporation
• Addition of anti-solvent
• After solubility of samples changed by temp/pressure/ph of the system

Question 10

Name and describe the different steps involved in the crystallisation process?

Answer 10

-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

Question 11

In order to achieve nuleation and growth the solution must not be supersaturated. TRUE OR FALSE?

Answer 11

FALSE

Question 12

What is polymorphism?

Answer 12

• When a crystalline state solid possesses
• different crystalline forms
• Different packing pattern
• Different lattice energies
• Different properties

Question 13

Polymorphism can present in a stable and metastable form. TRUE OR FALSE?

Answer 13

TRUE

Question 14

Describe both stable and metastable form of polymorphism

Answer 14

Stable form - Higher MP, slower dissolution rate

Metastable form - Lower MP, faster dissolution, increase in apparent solubility

Question 15

Metastable form will transform into most stable form. TRUE OR FALSE?

Answer 15

TRUE

Question 16

What is monotropic polymorphism?

Answer 16

-Only one stable polymorphic form (metastable will transform into stable over time)

Question 17

What is enantropic polymorphism?

Answer 17

-Material reversibly transformed between alternative stable forms.

Question 18

Which one is less common, monotropic or enantropic polymorphism?

Answer 18

Enantropic

Question 19

During crystallisation the solvent molecules can be trapped in the crystal lattice. TRUE OR FALSE?

Answer 19

TRUE

Question 20

What is monohydride and dihydride?

Answer 20

• Monohydride: 1 molecule of water:Molecule substance

- Dihydride: 2 molecules of water: 1 Molecule substance

Question 21

What is a solvate?

Answer 21

-Another solvent instead of water e.g organic solvents such as ethanol

Question 22

What is pseudopolymorphism?

Answer 22

-Used to describe the different between hydrates and anhydrous forms

Question 23

The hydrate form can have a slower or faster dissolution. TRUE OR FALSE?

Answer 23

TRUE

Question 24

Describe the properties of amorphous state?

Answer 24

• lower packing efficiency (less ordered)
• Greater intemolecular distance
• Greater molecular mobility
• Greater potential energy
• Often higher solubility

Question 25

Why are solids amorphous?

Answer 25

- 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

Question 26

Low MW materials are commonly amorphous. TRUE OR FALSE?

Answer 26

TRUE

Question 27

Larger MW compounds such as polymers disordered exhibit both ordered and disordered region - semi crystalline. TRUE OR FALSE?

Answer 27

TRUE

Question 28

Degree of crystallinity results in different properties. TRUE OR FALSE?

Answer 28

TRUE

Question 29

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?

Answer 29

TRUE

Question 30

What occurs when Tg is greater?

Answer 30

- Glassy brittle state | - Lower mobility of molecules

Question 31

What occurs when Tg is less than?

Answer 31

- Rubbery | - Higher mobility of molecules

Question 32

What are plasticisers and provide an example of a good plasticiser?

Answer 32

- Substances added to reduce Tg of an amorphous material | e. g Water

Question 33

At relatively high humdity's amorphous materials do not absorb water. TRUE OR FALSE?

Answer 33

FALSE

Question 34

Plasticising material with water leads to the reverting to the crystalline state leading to weight loss. TRUE OR FALSE?

Answer 34

TRUE

Question 35

What is crystal habit?

Answer 35

- Eternal shape of the crystal due to rate of crystal gowth at different faces influenced by crystalline conditions.

Question 36

Crystal habit can be different for different internal packing but also different for the same packing. TRUE OR FALSE?

Answer 36

TRUE

Question 37

Crystal habit affects drug properties, such as dissolution rate, powder flow and stability. TRUE OR FALSE?

Answer 37

TRUE