physical properties of matter

Question 1

what are aerosols

Answer 1

pharmaceutical aerosols are pressurised packages that contain the therapeutically active ingredient: dissolved, suspended or emulsified
in a propellant which id capable of expelling the product through N opened valve
OR
dispersion of a solid or liquid as very fine particles in a gas

Question 2

types of aerosols

Answer 2

metered dose inhalers MDI, nebulisers or DPI dry powder inhaler

Question 3

MDI

Answer 3

metered dose inhaler, most common, aerosol created when valve is opened, drug usually created in small particles suspended in liquid propellant or can be dissolved in the propellant, propellant evaporates rapidly as leaves device leaving drug to be inhaled

Question 4

nebulisers

Answer 4

oldest form, produce mist of a drug containing water droplets for inhalation, jet nebulisers use source of pressurised air to blast a steam of air through drug containing water reservoir producing droplets
electronic nebulisers use mechanical vibration of a plate or mesh to produce droplegs

Question 5

DPI

Answer 5

dty powder inhaler, aerosol is a powder until inhaled, often add large particles of lactose monohydrate to help entertainment of drug particles and make filling easier
upon inhalation, powder is broken ip into constituents by turbulence or mechanical device releasing drug to be inhaled in the lungs
sugar particles intended to be left in the device or in the mouth/throat

Question 6

liquified gas aerosol

Answer 6

canister contains propellant vapour and liquefied propellant
here, an equilibrium is established between the liquified propellant and its vapour, when valve is opened, the pressure forces some of the liquid up the dip tube and out into the atmosphere, the aerosol propellant vaporises and so disperses the active ingredients

although some if the liquid has now been used, equilibrium conditions are rapidly established by the vaporisation of more propellant and the original pressure is restored. the vapour pressure will therefore remain constant
nature of extrusion depends on both pressure and actuator

Question 7

propellants

Answer 7

used to be chlorofluorocarbons CFCs(propellant gas) but they destroy ozone layer
so now replaced by hydrofluoroalkanes HFAs
most common HFA 134a and HFA 227

Question 8

compressed gas aerosol

Answer 8

canister contains compressed gas and solvent

here an inert gas under pressure is used ticexpel the liquid. the pressure in the canister falls during usage

Question 9

vapour pressure

Answer 9

id increase temperature then increase motion of the liquid leads to greater tendency fir escape into vapour phase.
variation of vapour pressure with temperature may be expressed in terms of molar enthalpy of vaporisation of the liquid

Question 10

boiling points of liquids

Answer 10

the temp at which the vapour pressure of the liquid equals the prevailing atmosphere pressure, alters depending on pressure of enviroment

Question 11

molar enthalpy vapoeisation

Answer 11

the heat absorbed (constant pressure) when 1 mole of liquid vaporises at the normal b.p.

Question 12

clausius clapeyron equation

Answer 12

variation of vapour pressure with temp js described as clausius clapeyron equation
(graph of Log P against 1/T

Question 13

amorphous material

Answer 13

broad mpt range, globular in shape, isotropic, no diffraction, yield&flow

Question 14

crystalline material

Answer 14

narrow mpt range, regular faces and edges, anisotropic, diffract light, fracture/cleave under pressure

Question 15

3 steps to crystallisation

Answer 15

supersaturation, formation of nuclei, crystal growth

Question 16

diffraction and crystals

Answer 16

crystals diffract X-rays because the molecules are arranged in an ordered fashion. when an x ray beam strikes a crystal surface at some angle, part of the beam is scattered by the layer of atoms at the surface. the unscattered part of the beam penetrates to the second layer of atoms where again a fraction is scattered and so on.
the cumulative effect of this scattering from the regularly spaced centres of the crystals is diffraction of the beam in the same way as visible light is diffracted by a reflection grating
may be viewed as reflections from crystal planes. the distance between bonded atoms are comparable to the wavelength of the x ray beam

Question 17

why do x rays scatter

Answer 17

it is the electron clouds of the atoms in the crystal that scatter the x rays. the amount of scatter depends on the atomic number Z. a crystal has atoms/ions/molecules in identical positions and so the x rays are scattered in an identical way
this leads to a diffraction pattern which is seen as a series of spots on an imaging plate. the electron density indicated by the pattern can be reconstructed using a computer allowing bond lengths and angles to be determined

Question 18

what is braggs law

Answer 18

for constructive interference 2dsin theta =n lambda
diffraction observed if x rays scattering from a plane add in phase
path difference =2d sin theta = difference between 2 layers. d is the spacing between planes and theta is angle of incidence. scatted in phase if path difference is n lambda
n is integer and lambda in x ray wavelength

Question 19

what are crystal lattices

Answer 19

regular 3D arrangements of equivalent lattice points in space
lattice points define unit cells -smallest repeating internal unit that has the symmetry characteristic of the solid - an atom, ion or molecule

Question 20

cubic unit cells

Answer 20

all sides equal length, all angles 90 degrees
can get: primitive cubic(PC 1 atom), body centred cubic (BCC 2 atoms), face centred cubic (FCC4 atoms)
simple cubic unit cell- each atom is a corner of a unit cell and is shared among 8 unit cells. each edge is shared with 4 cells, each face is part of two cells

Question 21

diffraction from a single crystal

Answer 21

a rays striking a single crystal will produce diffraction spots in a sphere around the crystal. each diffraction spot corresponds to a single point in the lattice. the distribution of diffraction spots is dependent on the crystal structure and the orientation of the crystal in the diffractometer

Question 22

crystal habits

Answer 22

compounds crystallise into different habits (morphologies)

they usually have the same internal structure and the same x ray patterns

Question 23

what is polymorphism

Answer 23

polymorphism occurs when the molecules are arranged in two or more different ways
e,g, carbon (graphite, diamond, buckminsterfullerene)
they are packed differently in the crystal lattice, differences in the orientation or conformation of the molecules, this causes differences in the x-ray diffraction pattern
other differences include m.p., solubility, different habits

Question 24

solid state properties

Answer 24

the unit cell of polymorphic crystals have different dimensions
the preparation of different polymorphs involves manipulating the conditions of crystallisation
polymorphic changes may occur during processing:
density, m.p., hygroscopicity, electrical and optical properties, physical and chemical stability, dissolution velocity and apparent solubility
drug produce stability, dissolution and bioavailability, quality, safety and efficacy of drug product

Question 25

bioavailibility

Answer 25

rate and extent to which a substance is absorbed and circulated around the body
due to different solubilities and dissolution fates for some polymorphs, marked differences in bioavailability can occur

Question 26

characterisation of polymorphs

Answer 26

methods used to characterise polymorphs;
demonstration of an inequivalent substance by single crystal x ray diffraction is currently regarded as the definitive evidence of polymorphism
x ray powder diffraction cam also be used to provide unequivocal proof or polymorphism
other methods include microscopy, thermal analysis and spectroscopy

Question 27

DSC

Answer 27

differential scanning calorimetry (DSC) can detect different melting points if they exist, also ant solid-solid transitions caused by one form changing into another can be detected as an endothermic peak

Question 28

TGA

Answer 28

thermal gravimetric analysis
constant hearing rate
initial and final temp, heating rate
data - weight v tune and weight v temp

Question 29

hot stage microscopy

Answer 29

can detect different m.p. and see transitions
can detect the loss of solvent by covering in solicone oil, indicated by the formation of bubbles at appropriate temp. this enables us to distinguish between solvates and polymorphs

Question 30

the fourth state of matter

Answer 30

liquid crystal
liquid- flows, isotropic properties, optically transparent, 1 refractive index
crystal- doesn’t floe, anisotropic properties, direction dependant, 3 refractive indices
LC s ads orientationally ordered fluids
they are mesogens

Question 31

liquid crystal phase

Answer 31

esophase

Question 32

clearing temperature

Answer 32

the LC temp higher than isotropic phase transition temp

Question 33

thermotropic definition

Answer 33

behaviour as a function of temp
organic
elongated, flat, rigid along axes, contain dipoles and easily polarisable groups
may be orientated by electric or magnetic fields

Question 34

lyotropic

Answer 34

solutions of compound exhibit LC behaviour

Question 35

birefringence

Answer 35

ability to rotate plate of plane polarised light with more than or 2 refractive indicies

Question 36

types of LC

Answer 36

thermotropic (temp dependant)

• nematic (thread like)-orientational ordering
• smectic (soap like)reaches at lower temp than nematic- more order-layer ordering
• cholesteric(similar to nematic only in helices)

lyotropic (formed in solutions)

Question 37

thermotropic LC phases and ordering

Answer 37

crystalline solid, long range ordering
smectic, layer ordering
isotropic liquid, random ordering
nematic, orientational ordering

Question 38

liquid crystal display devices

Answer 38

LCD, weak electrical signal>optical response.
don’t emit light- modify by scattering;change in optical density or colour
low operating voltages compatibles with LCs
low power consumption, less heat produced
good contrast in strong light

Question 39

chirality and LCs

Answer 39

reinitiser- interaction between asymmetric molecules
cholesteric phase- chiral nematic
molecules want to be parallel but due to chiral interaction there is a slight angle between them
cholesteric LCs reflect light with a wavelength equal to the pitch, the pitch depends on temp so colour reflected also depends on temp, pitch also depends on pressure, electric and magnetic fields

Question 40

lyotropic LCs

Answer 40

solvent induced aggregation of molecules
solution exhibit liquid crystallinity
essential structural features; amphiphillic, 2 distinct regions within molecule (polar and non polar)

Question 41

micelle formation

Answer 41

very low surface concentration, monomeric solution
CMC- hydrophobic effects, monomers>spherical aggregates
micellar solution increase surface conc