Density of Glass Fragments
Purpose:
1. To explore how the density of an object is determined.
2. To determine what a "physical property" is.
3. To demonstrate how science can be applied to police work.
Student Objectives:
1. Students will be able to determine the density
of five glass fragments.
2. Students will be able to list three physical properties of glass.
3. Students will be able to conclude which known glass sample matches
the crime scene glass fragment.
Materials Needed:
1. Five glass fragments from different sources - for
example: mirror, Plexiglas, window, light bulb, tempered glass - all
sample should be the same color
2. Graduated Cylinders
3. Scales
4. Lecture Handouts
5. Lab Handouts
6. Homework Sheets
7. Yellow Crime Scene Tape
8. Small Envelopes
9. Forceps or Tweezers
Anticipatory Set:
1. Have warm up question posted on the board as students
enter the room - "How can an investigator differentiate one glass
sample from another?"
2. After students complete the warm up question, tell them the crime
scene story - "There was a hit and run car accident in the school
parking lot this morning. The police have requested that the students
from this class compare the glass fragments found at the crime scene
with those taken from two suspect vehicles. You will need to report
your findings to the police department as soon as possible."
3. Take students to the "crime scene" and have them collect
the evidence.
Procedures:
1. Complete the anticipatory set as described above.
(Day 1)
2. Pass out lecture notes and discuss in class.
3. Pass out lab handouts. (Day 2)
4. Divide class into groups of three or four.
5. Model the procedure for finding density, and then allow students
to complete their lab.
6. Hand out homework assignment.
Closure:
2. Day 1 - Have students answer the following before
leaving class - "List two things you learned today."
3. Day 2 - Have students answer the following before leaving class -
"List two physical characteristics of glass fragments you observed
during the lab."
Adaptations:
1. Learning support and lower ability students may
be provided with an outline containing fewer spaced while gifted students
may be provided with a minimal outline or no outline at all.
2. The lab will be conducted in mixed ability cooperative learning groups;
therefore, no adaptations are required.
Reinforcement Activity:
1. The laboratory exercise will require students to
use information from the lecture.
2. Students will have a homework assignment which uses the information
they gathered in the lab exercise.
Student Evaluation:
1. Students will be assessed by quizzes throughout
the forensics unit to ensure that they comprehend and can apply the
concepts.
2. At the end of the unit, students will be divided into groups for
a "unit activity." Students will be required to collect and
evaluate evidence from staged crime scenes. The evidence evaluation
will require them to apply the techniques taught throughout the unit.
Students will also be required to develop a report on the results of
their tests and their conclusion about the perpetrator, individually
after collaboration on the data.
Lesson Evaluation:
1. The lesson will be evaluated based on the homework,
lab handout, and quiz scores throughout the unit. All students will
be expected to receive a minimum score of 80%.
2. The lesson will also be evaluated based on the final "crime
scene" project, on which students will be expected to receive a
minimum score of 80%.
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