Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

CH1301 > chemistry against crime > Flashcards

chemistry against crime Flashcards

1
Q

what are the 3 steps of the forensic process

A

identification, classification, individualisation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the 2 types of evidence

A
  1. inclusive
  2. exclusive
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is inclusive evidence

A

ensures a person or object remains under study

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is exclusive evidence

A

excludes a person or object from further study.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is circumstantial evidence?

A

evidence requiring interference to move to a conclusion.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how do you measure the absolute error ?

A

EA = X - X(true)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how do you measure the relative error ?

A

ER = ((X - Xtrue) / Xtrue ) x 100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what does NUSAP stand for to help you quote uncertainties

A

number, units, spread, assessment, pedigree

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what does calibration mean ?

A

the comparison of measurement values delivered by a device under test with those of a standard of known accuracy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what does standard mean?

A

object, system or experiment that bears a defined relationship to a unit of measurement of a physical quantity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are the 2 main methods of producing alcohol?

A
  1. petrochemically (hydration of ethane)
  2. fermentation (metabolism of sugar by yeast In the absence of oxygen)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

how many mg of alcohol does it take to be fully drunk?

A

150-200

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

how many mg of alcohol in breath to drink in the Scotland ?

A

<22ug / 100ml

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is the process of the metabolism of alcohol in the blood?

A

ethanol -> acetaldehyde -> acetic acid -> CO2 + H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the wind mark equation

A

calculates the maximum amount of alcohol you could find in someones body.

c = 100 x a/( w x r)

a = amount of alcohol
c = peak concentration of alcohol (mg / 100ml)
w = mass of drinker (kg)
r = windmark factor (0.65 for males, 0.55 for females.)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are the 4 methods you can use to detect alcohol in someone’s breath

A
  1. chemical oxidation
  2. fuel cell detector
  3. IR absorption
  4. gas chromatography
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is the chemical oxidation method of alcohol testing

A

suspect blows into the metre where 50ml of the breath fills a small chamber which is bubbles through with dichromate. light sensitive detector measures the conversion to chromate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is the IR absorption method of alcohol testing

A

suspect blows into metre and first portion of breath discarded and final portion captured in gas cell. IR passed through sample and absorption analysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what are 3 common errors in alcohol breath testing

A
  1. temperature variation
  2. poor calibration of instuments
  3. interfering compounds.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what are the 4 ways drugs can be classified

A
  1. by their origin
  2. by the affect they have on the body
  3. by use
  4. by legislation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is pharmacokinetics

A

the study of the movement of a drug and its metabolic products through the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is the marquis colour test

A

used to identify drugs. each Turning a different colour. heroin = deep purple

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is the duquenois Levine colour test ?

A

test for cannabis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is the Scott colour test?

A

test for cocaine

25
Q

what 2 methods are used for drug profiling ?

A

gas chromatography
mass spectrometry

26
Q

what does mass spectrometry help us determine in drugs

A

the number of different isotopes in the compound.

27
Q

what’s an example of a athlete who was banned due to doping

A

lance Armstrong, famous cyclist and 7 time winner of the tour de France.

28
Q

what reactions take place in a flame?

A

we make the products of the combustion reaction,

we make many intermediates including C, H, CH4, CHO …

finally we make free radicals. - reactive species with unpaired electrons

29
Q

what is an incendiary device?

A

devise designed to ignite fire often involving time delay

30
Q

what is headspace analysis ?

A

it is the analysis of fire debris, trying to detect accelerants.

31
Q

what are the 4 steps of headspace analysis ?

A
  1. fire debris is collected in metal tin with predrilled hole.
  2. sealed with airtight seal, trapping residual volatile accelerants
  3. gentle heating caused the vaporisation of volatile species
  4. gas above the debris is drawn off using syringe though the pre drilled hole
32
Q

how do you analyse the removed gasses from headspace analysis.

A

mass spectrometry and gas chromatography

33
Q

how does gunshot work ? 5 steps

A
  1. primer is ignited by pulling the trigger
  2. ignites the propellant
  3. propellant expands, sending high speed pressure waves down the gun
  4. propels bullet from the gun
  5. if speed of sound exceeded a cracking sound is heard
34
Q

what is the metal test use on gunshot residue

A

spray exhibit with a weak solution of sodium rhodizonate (orange solution).

red/pink colour formed if lead present.

35
Q

what is the difference between deflagration and explosion?

A

in deflagration the Flames travel at subsonic speeds, which are slower than the speed of sound. Deflagrations are also known as low explosives.

explosion is just the general term for a rapid decomposition of a chemical mixture

36
Q

what is the explosive power index

A

= Q V(explosive) / Q V(picric) x 100

Q = heat produced
V = volume of products

37
Q

what are the tests run on explosive residue

A

identification :
gas chromatography
mass spectrometry

tests for nitrates and nitrites :
Griess-type tests
dpa test

38
Q

what are griess type tests (tests for nitrites)

A

treat photographic paper with a mixture of sulfanilic acid and naphthol.

place face down on clothing

steam iron use acetic acid

orange colour formed if nitrite present

39
Q

what is the dpa test (nitrates) for gunshot residue

A

diphenylamine.

add No3- and blue colour will form if nitrate is present.

40
Q

what’s the test for screening explosives ( detecting them before they explode)

A

ion mobility spectrometry

41
Q

what’s a taggant

A

chemical or physical marker added by manufactures to allow testing.

42
Q

what is the process of the drunkometre

A

subject would breathe into devise and would be pumped though acidified potassium permangate solution.

if the solution changed colour it would indicate there was alcohol in their breath. the bigger the colour change the more alcohol present.

43
Q

what is the difference between the primer and the propellant and which would be the easiest to detect in gunshot residue?

A

the primer is a chemical which ignited the propellant.

the primer is easier to detect as there are more methods to detect it such as

  1. tests for nitrates and nitrite s
  2. tests for metals
44
Q

what is the chain of custody

A

info on how and when evidence is collected

  • info of how sample is transported.
  • info on security when sample is stored.
  • info on how and when evidence was collected
45
Q

how would you determine if two drugs samples are from the same batch

A
  1. gas chromatography
  2. mass spectrometry
46
Q

what is meant by positive bias

A

systematic error where the answer is consistently higher than the true or actual value

47
Q

why might a measurement by bias ?

A

contamination
instrument errors
handling errors

48
Q

what is the units for the answer in the wind mark equation

A

mg / 100 ml

49
Q

what is meant by the explosive power index

A

a measure of the explosives material energy output compared to picric acid.

50
Q

why are presumptive tests useful ?

A
  1. test is simple
  2. rules out possible conclusions fast
  3. easy to do at a. crime scene
  • these are not good enough evidence to use at court!
51
Q

what is a test for NOx

A

Griess test - …

52
Q

what is locards principle

A

‘every contact has a trace’

53
Q

what is the analyte

A

the compound / thing which is the subject of the analysis

54
Q

what is the matrix

A

remainder of the compound which the alalyte forms a part of

55
Q

what is the names of the 2 blood tests

A

Kastle-Meyer and Luminol

56
Q

what would you add to cociane

A

caffeine

57
Q

what would you add to herion

A

quinine

58
Q

what does thinner mean

A

not active, just dilutes the drug

59
Q

what does adulterant

A

active with similar effects to the drug

CH1301 (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions