Thermal analysis Flashcards
What are the states of matter
solid
liquid
gas
what is glass transition
transition in amorphous materials from a hard and relatively brittle state into a molten or rubbler like state
what is melting
physical process that in the phase change of a substance from a crystalline solid to a liquid
what is boiling
rapid vaporisation of a liquid which occurs when a liquid is heated to its boiling point
is glass transition reversible
yes
what is sublimation
is the chagne from a solid to a gas without entering liquid phase (reversible)
what is decomposition
procces by which material is broken down into simpler forms of matter
what is denaturation
structural changes of biopolymers that involves the disruption and possible destruction of both the secondary and tertiary structures
what is oxidation
combination of a substance with oxygen
what are the main components of a hot stage microscopy
an optical microscope a polarising filter a heating stage an optional cooling stage an optional video camera
what is thermogravimetric analysis commonly known as
TGA
what is TGA
sample weight change is measured as a function of temperature, where temperature is varied in a controlled manner.
how will weight of process change during TGA
glass transition no change
melting no change
denaturation no change
boil and evaporation will decrease
sublimation will decrease
decomposition will decrease if at least one of the products is a gas or a volatile liquid
oxidation will increase
how does single stage and multistage decomposition on TGA thermogram
single stage will have one consistent drop multiple drops
what is differential thermogravimetry
thermal analysis in which the rate of material wieght change upon heating versus temperature is plotted
what is DTG (differential thermogravimetry)
used to simplify reading of weight vs temperature thermogram peaks that occur close together
what are the applications of thermpgravimetry
water content residual solvent composition of multicomponent systems thermal stability of materials oxidative stability of materials estimated lifetime of a product decomposition kinetics of materials
what is endothermic
a process that involves the taking in of heat from the surroundings
what is exothermic
a process that involves the release of energy to the surroundings
how do we calculate gibbs free energy
^G = ^enthalpy change - Temperature ^entropy change
what does a negative delta H mean
exothermic
what does a positive delta H mean
endothermic
what is differential scanning calorimetry
when a material undergoes a change in physical state or when it reacts chemically, heat is either absorbed or liberated.
The DSC instrument keeps the sample and inert reference material at the same temperature while the sample is heated or cooled
what is the energy required to maintain delta = to
0
what is the implication of the enegery required to maintain temperature difference
gives calorimetric measurements directly
what does a peak on a DSC scan mean
endotherm
what does a dip on a DSC scan mean
exotherm
what is the flow of purge gas used for
provide a dry inert atmosphere aid heat flow & carry away gases
what is the typical scan rate of DSC
10 degrees per minute
what are the applications of DSC
melting and decomposition points
purity measurements
how can we find the degree of drug crystallinity in mixtures
find enthalpy of melting of pure crystalline drug
find the enthalpy of melting of drug in a mixture
enthalpy of melting drug x ws/wh ) / determine the enthalpy of melting of pure 100% crystalline drug
what is ws
weight of sample
what is wh
weight of drug
what is TGA useful for
Useful for transformations involving the absorption or evolution of gases from a condensed matter phase.
