Do Not Write on Test

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