Solid States

Question 1

Molecules aggregate in different ways and have different phases (g,l,s). TRUE or FALSE

Answer 1

TRUE

Question 2

Name 3 differences between gas, liquids and solids

Answer 2

1) Diff intermolecular distances
2) Diff molecular orientations
3) Diff energy levels

Question 3

Gas and liquid display ‘no packing order’. TRUE or FALSE

Answer 3

TRUE

Question 4

Solids displays ‘highly ordered packing’. TRUE or FALSE

Answer 4

TRUE

Question 5

Does intermolecular distance increase or decrease from Gas…Liquid…Solid ?

Answer 5

Decrease

Question 6

Does molecular orientation/mobility increase or decrease from Gas…Liquid…Solid ?

Answer 6

Decrease

Question 7

Does potential energy increase or decrease from Gas…Liquid…Solid ?

Answer 7

Decrease

Question 8

Name 9 physiochemical properties that impact solid state

Answer 8

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

Question 9

State the 2 types of Solids

Answer 9

Amorphous (non-crystalline) and Crystalline

Question 10

State the 3 classes of Crystalline solids

Answer 10

1) Polymorphs
2) Co-crystals
3) Hydrates and Solvates

Question 11

Define ‘Crystalline state’

Answer 11

Molecules arranged in orderly, defined manner. W/same repeating units

Question 12

Crystalline solids have HIGHER potential energy than amorphous state. TRUE or FALSE

Answer 12

FALSE. They have lower potential energy

Question 13

Define ‘Polymorphism’

Answer 13

Repeating units arranged differently within the crystalline form (of the same substance)

Question 14

Diff crystalline forms of the same substance have different MP’s. TRUE or FALSE

Answer 14

FALSE

Question 15

State 3 methods of crystallisation

Answer 15

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)

Question 16

Describe the Crystallisation process

Answer 16

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

Question 17

To achieve Nucleation and growth, the solution must be supersaturated. TRUE or FALSE

Answer 17

TRUE

Question 18

Polymorphism describes a crystalline solid sate that possess different … ?

Answer 18

• Crystalline forms
• Packaging pattern
• Lattice energies
• Properties

Question 19

State 2 properties of ‘Stable form’ polymorphism

Answer 19

1) High MP

2) Slow dissolution rate

Question 20

State 3 properties of ‘Metastable form’ polymorphism

Answer 20

1) Lower MP
2) Faster dissolution
3) Increase in apparent solubility

Question 21

The conversion of metastable to stable form can be fast or slow depending on 2 things. What are they ?

Answer 21

1) Energy difference of both forms

2) Environmental conditions

Question 22

Define ‘Monotropic polymorphism’

Answer 22

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

Question 23

Define ‘Enantropic polymorphism’

Answer 23

Material is transferred b/wn alternative stable forms. Less common

Question 24

Describe the difference in solvent between Hydrate and Solvate

Answer 24

Hydrate; Solvent = Water

Solvate; Any solvent besides water e.g: Organic solvents -ethanol

Question 25

‘Pseudopolymorphism’

Answer 25

Term used to describe the difference b/wn hydrates and anhydrous form

Question 26

What is the slow dissolution rate of hydrates due to ?

Answer 26

Water strengthens the lattice e.g: Theophylline

Question 27

What is the fast dissolution rate of hydrates due to ?

Answer 27

Water weakens the lattice e.g: Erythromycin

Question 28

Why are solids amorphous ?

Answer 28

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

Question 29

State 5 properties of Solid Amorphous state

Answer 29

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

Question 30

Low MW materials are usually Amorphous. TRUE or FALSE

Answer 30

TRUE

Question 31

Larger MW compounds (e.g: Polymers) exhibit both ordered and disordered region aka Semi crystalline. TRUE or FALSE

Answer 31

TRUE

Question 32

What is Tg ?

Answer 32

Glass Transition temperature

Question 33

Define ‘Plasticiser’ and give a example of a plasticiser

Answer 33

A substance that is added to reduce Tg of an amorphous material. e.g: Water

Question 34

At —- humidity, amorphous material absorb water (and may become crystalline). Fill in the gap

Answer 34

high

Question 35

Water increases the molecular mobility of Amorphous materials. TRUE or FALSE

Answer 35

TRUE. Increased molecular mobility results in ordered alignment of molecules

Question 36

What does ‘Crystal habit’ describe ?

Answer 36

The external shape of a crystal

Question 37

Give examples of drug properties crystal habit has an effect on

Answer 37

• Dissolution rate
• Powder flow
• Stability (sedimentation rate and caking of suspension)