Forensics Ch. 5, 6, 7 Study Guide Answers
1. Give an example of an element. How many known elements are there?
Aluminum Al, Over 115 known elements
2. What is chromatography?
A technique of separating and tentatively identifying the components of a mixture is
3. Describe how chromatography occurs.
One phase must move continuously in one direction over a stationary phase
4. Describe Henry’s Law.
The distribution of a volatile chemical compound between its liquid and gas phases
5. How are gas chromatography and thin-layer chromatography different?
GC separates mixtures on the basis of their distribution between stationary liquid phase and a moving gas phase
TLC uses a moving liquid phase and a stationary solid phase to separate mixtures
6. What is retention time?
The time required for a substance to travel through the gas chromatographic column is a useful
identifying characteristic
7. A big drawback of gas chromatography is that is does not produce specific identification. This problem is overcome
by connecting the GC to what other machine?
Mass-Spec
8. Define spectrometry.
The study of the absorption of light by chemical substance
9. True or False: Many chemical substances have similar mass spectra fragmentation patterns
False
10. Name one analysis technique that yields positive identification of a material.
Infrared, GC-MS, X-ray diffraction
11. Identify what a spectrophotometer is used for.
Used to measure and record the absorption spectrum of a chemical substance.
12. In neutron activation, what bombards the specimen to generate gamma rays?
Neutrons
13. How are real and virtual images different?
Real = image is viewed directly
Virtual = A type of image that cannot be viewed directly, seen through a compound microscope
14. Describe what the objective lens and ocular lens are on a microscope
Objective = The lens closest to the specimen
Ocular = The lens nearest the viewer’s eye
15. Define monocular and binocular
Mono = one eyepiece, bino = two eyepieces
16. Name the four pieces of a compound microscope.
Abbe condenser, Objective lens, Eyepiece lens, The illuminator
17. What is a compound microscope?
A microscope consists of two lenses mounted at each end of a hollow tube
18. What is the role of the condenser?
To collect light rays from the base illuminator and concentrates them on the specimen
19. State the role of a comparison microscope.
To provide a side-by-side view of two specimens
20. Which type of microscope and light would you use to examine a bullet?
Comparison, reflected
21. What type of illumination is used to view opaque objects?
Vertical or reflected
22. Describe Beer’s Law
The amount of radiation a substance will absorb is directly proportional to its concentration
23. How is the magnification power of microscope determined?
Objective lens multiplied by ocular (eyepiece) lens