Lecture 13: Metals, Paints and Soil Flashcards

1
Q

What role do trace elements play in materials?

A

Trace elements act as invisible markers to identify the material source or aid in comparisons.

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

What is the significance of comparing emission spectra in chemistry?

A

Comparing emission spectra allows for element identification by matching line by line between samples.

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

How does an Emission Spectrograph work?

A

Samples are vaporized, atoms emit light, and the line spectrum identifies elements by characteristic frequencies.

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

Describe the structure of atoms in the context of the origin of spectra.

A

Atoms have a nucleus with protons and neutrons and electrons in specific energy level electron orbitals.

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

How are electron orbitals related to energy levels in the context of spectra?

A

Electron orbitals are associated with specific energy levels and contribute to the origin of spectral lines.

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

What happens when an atom absorbs a definite amount of energy?

A

Electrons move into higher energy levels, creating an excited state.

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

How does an atom release energy that it absorbed?

A

Electrons return to their original energy levels, emitting energy in the form of light.

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

What does emission spectroscopy measure in atoms?

A

It measures the light energies emitted by atoms.

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

How is the specific frequency of absorbed or emitted light determined?

A

It is determined using the relationship E = hf, where E is the energy difference between orbitals, h is Planck’s constant, and f is frequency.

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

How does Inductively Coupled Plasma Emission Spectrometry (ICP) work?

A

It introduces an aerosolized sample into a hot plasma to create charged particles emitting light of characteristic wavelengths.

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

What are the key components applied by automobile manufacturers to car bodies?

A

Electrocoat primer, primer surfacer, basecoat, and clearcoat.

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

Why is binder significant in automotive paint?

A

Binder hardens to trap pigments, create a protective barrier, and enhance paint functionality beyond color.

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

What role do pigments play in paint, and how are they distributed?

A

Pigments provide color and are suspended (not dissolved) in the paint, requiring stirring before use.

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

What is the function of drying agents in paint?

A

Drying agents facilitate quick and even drying of paint.

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

How are questioned and known paint specimens compared in forensic investigations?

A

They are compared under a stereoscopic microscope for color, surface texture, and layer sequence to individualize paints based on their complex layer structures.

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

How do paint samples reveal the composition of compounds in the sample?

A

Paint samples are analyzed using Gas Chromatograph/Mass Spectrometer to show unique combinations of binders, delusterants, and pigments.

17
Q

What technique is used to distinguish paint binder formulations?

A

Pyrolysis Gas Chromatography and Infrared Spectrophotometry utilize high temperatures to decompose paint into gaseous products for analysis.

18
Q

How are elements in paint pigments identified?

A

Emission spectroscopy or X-ray spectroscopy methods are employed to identify the elements present in paint pigments.

19
Q

What is a crucial aspect of forensic analysis related to paint?

A

Crime labs can identify car make and model from tiny paint samples using color charts or the PDQ database.

20
Q

Why are objects typically covered in multiple layers of paint?

A

Objects have primer coats for protection and adhesion, and top coats for color, serving as evidence through the color layer sequence.

21
Q

Why is collecting uncontaminated reference paint important in hit-and-run cases?

A

Uncontaminated reference paint offers a baseline for comparison in forensic analysis to identify the source of paint chips found in hit-and-run incidents.

22
Q

How should paint samples be stored for analysis in forensic investigations?

A

Paint samples should be stored in paper druggist folds or glass/plastic vials to prevent contamination and preserve the integrity of the evidence.

23
Q

Why should garments or objects with smeared or embedded paint be sent entirely to the laboratory for analysis?

A

ending garments or objects entirely ensures that all relevant paint traces are preserved for thorough forensic analysis, aiding in identifying the source

24
Q

How can different soils be distinguished in forensic analysis based on visual examination?

A

Soils can be differentiated by color, texture, and other gross appearance features that help forensic experts classify and compare soil samples from various origins.

25
Q

What characteristics do forensic geologists analyze to compare soil samples?

A

Forensic geologists focus on mineral content, color, texture, shapes, and the presence of foreign objects to characterize and differentiate soil samples.

26
Q

What should be noted in terms of material when conducting forensic soil analysis under UV light?

A

Note the shape, size, number, and identity of any material that fluoresces under UV light.

27
Q

How should foreign objects found during soil analysis be handled?

A

Foreign objects found should be investigated separately to determine their origin and significance.

28
Q

How do similarities in previous comparisons between two soil samples guide forensic analysts?

A

Similarities in previous comparisons suggest that the samples likely originate from the same area.

29
Q

What are density gradient columns used for in forensic soil analysis?

A

Density gradient columns are used for a final comparison between soil samples to determine similarities in origin.

30
Q

Describe the process of using density gradient tubes in soil analysis.

A

Assemble two identical density columns, drop soil samples in them, allow dispersion, and compare; nearly identical tubes suggest same origins.