Glass Analysis Lab
Law Enforcement II
Forensics
Mrs. Ashley
Name ___________________________________
Glass Density
Materials:
(Per Group of three students)
Evidence bags containing glass labeled suspect 1, 2, 3, 4
Evidence bag from crime scene labeled CS
Graduated cylinder
Beaker
Water
Balance
Colored paper or newspaper
Forceps
Labeling tape
Permanent marker
Displacement container
Safety precautions: Wear gloves and safety googles while doing this lab. Pick up glass with a piece of
toweling, never directly handle glass. Spread newspaper or colored construction paper over your lab
area. Immediately report any accidents to your teacher.
Background: The density of glass fragments found at a crime scene can be compared to the glass
fragments found on suspects. Keep in mind that if the densities do match, this does not prove that the
suspect is guilty, because glass would be considered class evidence.
Glass fragments from a crime scene need to be matched with any glass fragments associated with the
four suspects. In this activity you are asked to determine the density of glass fragments found at the
crime scene and the densities of the glass fragments found on the suspects. If the densities do not
match, you may be able to disqualify a suspect. If you find that the densities do match, then you will
need to find further evidence to prove that the suspect was present at the crime scene.
Procedure:
1. Obtain the envelops labeled suspect 1, suspect 2, suspect 3, and suspect 4
2. Using suspect 1 evidence bag, record your name, date and time on the bag, showing you are
opening the envelop.
3. Open the envelop #1 and remove two pieces of glass fragments from #1. Using a scale, measure
the mass of the two pieces of glass and record the mass on table 1. Leave the glass on the scale.
4. Use a small beaker and fill to overflowing.
5. Position a clean, dry, small graduated cylinder to receive the overflow of water. You may need
to position books under the beaker to allow for overflow collection by the graduated cylinder.
6. Slowly add the two glass fragments to the beaker while you collect the water that is displaced in
the small graduated cylinder.
7. Measure this volume of water displaced by looking at how much is in the graduated cylinder.
8. Record the combined volume of the two glass fragments in Table 1.
9. Calculate the density of glass fragment 1 by dividing the mass by the volume (grams/ml).
Record this amount for density in Table 1
10. Remove the two glass fragments, place on a paper towel and then after a few minutes place
back in the evidence bag for #1.
11. Repeat for the crime scene glass.
Table 1
Sample
Combined Mass of
Two Fragments
Volume of Two
Fragments
Density (m/v)
(Grams/ml)
1
2
3
4
Crime Scene
Questions:
1.
Does the density of the glass fragments found on any of the four suspects match the
evidence found at the crime scene? Explain your answer.
2. Describe how you could improve your results to get more accurate results.
3. Describe why glass is considered class evidence.