Forensics Ch. 4 Study Guide Answers
1. How many centimeters are in one inch? 2.54
2. Which is longer – meter or yard? Meter
3. Which is larger – liter or quart? Liter
4. At what temperature does water boil? 100⁰ Celsius, 212⁰ Fahrenheit
5. Which physical state has both shape and volume? Solid
6. Define physical property. Describes the behavior a substance without reference to any other substance.
7. Give examples of physical properties of substances? Boiling point, color, weight
8. List some intensive properties of matter. Density, refractive index, temperature, specific heat
9. How is density determined Mass per unit volume
10. If an object has a greater density than the medium in which it is placed, what will it do? Sink
11. Describe the differences in densities between water at different temperatures?
Colder is more dense, warmer is less dense
12. What are the two most important physical properties of glass for forensic comparison?
Refractive index and density
13. A piece of glass is immersed in a liquid. It proceeds to float on the liquid’s surface. What does that tell you
about the density of the glass? Density of glass is less than that of liquid
14. What are the main ingredients of glass? Sand, silicon oxides and metal oxides
15. How is tempered glass used? Sides and rear windows of US autos
16. What causes the refractive index of a substance to vary? Temperature, wavelength of light, color
17. Describe the refractive index of crystalline solids. Are there any crystalline solids that do NOT exhibit this
characteristic? Double refraction, cubic
18. Glass fracture is made of two types of lines, what are they? Radial & Concentric
19. Describe what happens when a projectile impacts glass? Radial cracks appear first on opposite side of
force, concentric cracks go around the entrance, and the exit side is larger than the entrance side.
20. The larger opening in a glass fragments indicates what? The exit side
21. Where do radial cracks appear when a projectile impacts glass? Opposite the force
22. What does the 3R rule state? radial cracks form a right angle on the reverse side of the force
23. How can an investigator determine the order in which several successive penetrations of a glass occurred?
Points of termination
24. A store-front window is broken and a robbery is committed. A suspect is later found running from the
scene. Examination of his shoes reveals glass particles embedded in a heel. Describe the proper collection and
preservation of glass evidence for laboratory examination.
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a. Entire shoe submitted for laboratory examination. Avoid removing glass evidence from shoe
unless there is a distinct possibility that glass will be lost in transit
b. Shoes packaged in box or paper bag
c. Control glass from broken window submitted for examination as standard reference
d. Druggist fold provide convenient containers for small glass fragments
e. All packages properly labeled
Stress marks occur where in relation to the force? Parallel to the side force is applied
What is the first step you completed in soil analysis? Comparison of dried soil sample for color and texture
How are crystal minerals identified? Using color, geometric shape, and refractive index
When is a density gradient tube used? Soil analysis
Why is soil left in lump form when collected? Lumps exhibit a layering effect not found in loose soil.