Brainscape's Knowledge GenomeTM

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


See full index

CRIM 355 > Forensic Chemistry > Flashcards

Forensic Chemistry Flashcards

1
Q

What does forensic chemistry analyze?

A
  • non-biological trace evidence

ex: fibres, paint, glass, arson, explosives

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

What types of crimes does forensic chemistry cover?

A
  • break and enter
  • hit and run
  • arson
  • bombings
  • terrorism
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the 5 steps for analysis?

A
  1. determine substance (gasoline)
  2. determine distributor (Esso)
  3. determine batch (specific location and date)
  4. qualitative analysis (what substances were present?)
  5. quantitative analysis (% of each)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are 5 types of non-destructive analysis?

A
  1. visual inspection (colour, design, surface quality)
  2. microscopy (opacity, reflectance, refractive index)
  3. UV-Visible micro-spectrometry (pigments)
  4. Fourier-transform infrared spectrometry (wavelengths)
  5. micro x-ray fluorescence (inorganic materials)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is chromatography? List and describe the different types

A
  • separates substances into components (purifies them)
    1. Gas chromatography (GC)
  • separates based on distribution between liquid and gas phase
  • sample is injected, heated, broken down into gas, and analyzed
    2. Thin Layer Chromatography (TLC)
  • uses solid and liquid phase to separate components of mixture
    3. High-Performance Liquid Chromatography (HPLC)
  • liquid pumped through column filled with solid particles
  • as liquid moves through, sample in injected and carried through liquid
  • various components will be slowed as it passes through
    4. Pyrolysis
  • paint chips are heated into gaseous products and sent through GC
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is spectrophotometry?

A
  • analyzes how different substances absorb light in different ways
  • GC + MS = positive ID
  • GC alone is tentative ID
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How is significance evaluated?

A
  • identifying substance
  • class evidence
  • may have low or high significance (rare = more significant)
  • how common is the evidence?
  • develop database and determine parent population
  • how valid is database?
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the two types of fibres?

A
  1. natural - animal, mineral, vegetable

2. manmade - synthesized or originate from natural materials (made of polymers)

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

How are fibres examined?

A
  • colour, striations, cross section shape, refractive index
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What dictates the significance of a fibre?

A
  • circumstances of the case

location found, number and nature of fibres examined

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

Where can paint be found?

A

transportation - cars, bikes, boats, planes

household objects - walls, doors, window frames, paintings

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are some methods of paint examination?

A
  • visual and microscopic examinations
  • colour, shapes, surface properties, thickness of layers
  • physical match based on contours, scratches
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the 4 layers of car paint? How can it be used as class evidence?

A
  • primer, primer surface, colour, base coat, clear coat

- can match paint in database down to make, model, and year (PDQ)

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

How is glass examined?

A
  • comparing control sample from scene to recovered sample from suspect
  • need to look at thickness, elemental composition, refractive index, colour
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are 3 things fire investigators are responsible for at a fire scene?

A
  1. determining origin of fire (using fire patterns)
  2. determine cause of fire (what fuel was ignited first and fuel source)
  3. determining if arson or accidental
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Why are fire crime scenes more complex than regular crime scenes?

A
  • more dangerous, hot, and unstable

- scene is destroyed by fire then water (destroy evidence of accelerants)

17
Q

What is the role of a forensic chemist for a fire scene?

A
  • detect accelerants
18
Q

What are the 3 components of fire?

A
  • fuel (combustible material)
  • oxygen
  • source of heat (activation energy)
19
Q

List 6 things fire investigators need to look for/determine at a fire scene

A
  • assumption of arson
  • check for human remains
  • identify point of origin
  • search for accelerants
  • search for ignition devices
  • determine significance of accelerant
20
Q

How are samples collected from a fire scene?

A
  • debris is placed in a sealable gas-tight container
21
Q

Describe flame over and flashover

A

flame over:
- unburned fuel from originating fire has accumulated in ceiling layer and ignites and burns
flashover:
- surfaces exposed to thermal radiation reach ignition temps at the same time leading to full room involvement

22
Q

What are the disadvantages of flashover?

A
  • dangerous for firefighters

- obscures fire origin and consequently the cause

23
Q

What is an explosion? How does it differ from a fire?

A
  • product of combustion accompanied by creation of gases and heat
  • difference between fire is speed
24
Q

List and describe the 3 effects of an explosion

A
  1. blast/pressure wave
    - does the most damage
    - pressure wave that radiates outward from seat of explosion
  2. Fragmentation
    - device casing breaks into pieces
    - primary: shrapnel/fragments
    - secondary: other objects like glass struck
  3. incendiary/thermal component
    - high temps and localized
25
Q

How are explosions classified? Describe the 2 categories

A
  • classified based on speed at which explosive decomposes
    1. Low explosives: speed of deflagration
  • rapid oxidation, heat, light, subsonic pressure wave
  • slow burning rate = suitable for throwing or propelling action
  • unconfined = burns
  • confined = lethal due to shrapnel
    2. high explosives - speed of detonation
  • creates supersonic shock wave, and build up of heat and gases
    Primary:
  • ultra-sensitive to heat, shock, friction
  • detonate violently (used as detonators)
    Secondary:
  • insensitive to heat, shock, and friction
  • Burn rather than detonate in open air
26
Q

What is dynamite composed of? What are the disadvantages for forensic chemists?

A
  • composed of a ammonium-nitrate (manure)

- washes away easily, easily available, low significance

27
Q

What are common components of a bomb?

A
  • explosive
  • timer
  • detonator
  • fuses
  • batteries
  • casings

CRIM 355 (11 decks)

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