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Molecules and Medicine > Thermal analysis > Flashcards

Thermal analysis Flashcards

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Organic Chemistry 101 flashcards
1
Q

What are the states of matter

A

solid
liquid
gas

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2
Q

what is glass transition

A

transition in amorphous materials from a hard and relatively brittle state into a molten or rubbler like state

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3
Q

what is melting

A

physical process that in the phase change of a substance from a crystalline solid to a liquid

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4
Q

what is boiling

A

rapid vaporisation of a liquid which occurs when a liquid is heated to its boiling point

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5
Q

is glass transition reversible

A

yes

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6
Q

what is sublimation

A

is the chagne from a solid to a gas without entering liquid phase (reversible)

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7
Q

what is decomposition

A

procces by which material is broken down into simpler forms of matter

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8
Q

what is denaturation

A

structural changes of biopolymers that involves the disruption and possible destruction of both the secondary and tertiary structures

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9
Q

what is oxidation

A

combination of a substance with oxygen

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10
Q

what are the main components of a hot stage microscopy

A 
an optical microscope
a polarising filter
a heating stage
an optional cooling stage
an optional video camera
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11
Q

what is thermogravimetric analysis commonly known as

A

TGA

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12
Q

what is TGA

A

sample weight change is measured as a function of temperature, where temperature is varied in a controlled manner.

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13
Q

how will weight of process change during TGA

A

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

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14
Q

how does single stage and multistage decomposition on TGA thermogram

A

single stage will have one consistent drop multiple drops

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15
Q

what is differential thermogravimetry

A

thermal analysis in which the rate of material wieght change upon heating versus temperature is plotted

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16
Q

what is DTG (differential thermogravimetry)

A

used to simplify reading of weight vs temperature thermogram peaks that occur close together

17
Q

what are the applications of thermpgravimetry

A 
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
18
Q

what is endothermic

A

a process that involves the taking in of heat from the surroundings

19
Q

what is exothermic

A

a process that involves the release of energy to the surroundings

20
Q

how do we calculate gibbs free energy

A

^G = ^enthalpy change - Temperature ^entropy change

21
Q

what does a negative delta H mean

A

exothermic

22
Q

what does a positive delta H mean

A

endothermic

23
Q

what is differential scanning calorimetry

A

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

24
Q

what is the energy required to maintain delta = to

A

0

25
Q

what is the implication of the enegery required to maintain temperature difference

A

gives calorimetric measurements directly

26
Q

what does a peak on a DSC scan mean

A

endotherm

27
Q

what does a dip on a DSC scan mean

A

exotherm

28
Q

what is the flow of purge gas used for

A

provide a dry inert atmosphere aid heat flow & carry away gases

29
Q

what is the typical scan rate of DSC

A

10 degrees per minute

30
Q

what are the applications of DSC

A

melting and decomposition points

purity measurements

31
Q

how can we find the degree of drug crystallinity in mixtures

A

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

32
Q

what is ws

A

weight of sample

33
Q

what is wh

A

weight of drug

34
Q

what is TGA useful for

A

Useful for transformations involving the absorption or evolution of gases from a condensed matter phase.

Molecules and Medicine (23 decks)

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