McKenzie Doran
Activity 1.1.5: Time of Death Experimental
Design
1. Identify the Problem or Question
o State the research problem or question in one sentence.
o The problem should be very specific and measurable.
Write one sentence in the form of a question or problem statement.
Problem Statement: How do different ambient temperatures affect the rate of body
cooling?
2. Predict a solution to the problem or an answer to the question.
o This will be in the form of a hypothesis.
o This solution design or hypothesis should be based on previously
obtained knowledge or research and should be supported by
scientific evidence.
o Identify the independent and dependent variables.
o The independent variable is the variable that is varied or
manipulated by the researcher. The dependent variable is the
measurable effect, outcome, or response in which the researcher is
interested. In other words, the independent variable is the presumed
cause, whereas the dependent variable is the presumed effect. In
an experiment, the independent variable is the variable that is
controlled and manipulated by the experimenter; the dependent
variable is not manipulated but instead is observed or measured for
variations.
Write a one or two sentence statement predicting the outcome of the experiment.
In a separate statement, specify the independent and dependent variables.
Hypothesis:
If the ambient temperature of a dead body changes, then the rate of cooling will change.
The independent variable is: Ambient Temperature
The dependent variable is: Rate of Cooling; Body Temperature
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Principles of Biomedical Science Activity 1.1.5 Time of Death Experimental Design – Page 1
McKenzie Doran
3. Design the experiment to be used to test your hypothesis.
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Include a list of all materials used.
Be specific.
Take all safety concerns into account.
Identify a control to be used for comparison if applicable.
Control all outside variables that could affect the outcome of the
experiment.
o Clearly define how the data will be collected and recorded, including
measurement units.
o Design a data table to use to record information.
o Plan the strategy that will be used to summarize the data. For
example, a graph might be used to summarize the data.
Write a series of numbered steps and include a list of required materials. The
data table should include units that will be used to collect data.
Materials:
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3 Computers with Logger Pro software
3 Vernier Temperature Probes
Goggles
Gloves
Laboratory apron
Oven mitt
3 Ring stands with clamp
3 Test tubes
Sodium polyacrylate (also known as waterlock)
Weigh boats
Electronic balance
Thermometer
37˚C Water
Graduated cylinder
Hot water bath set to approximately 50˚C
Ice water bath
Room temperature water
Procedure:
1. Wear the appropriate personal protective equipment.
2. Create the following three water baths:
o A 250 mL beaker filled with 200 mL of water on a hot plate set to medium
heat that is approximately 50˚C.
© 2013 Project Lead The Way, Inc.
Principles of Biomedical Science Activity 1.1.5 Time of Death Experimental Design – Page 2
McKenzie Doran
o A 250 mL beaker filled with 200 mL of water at room temperature
(approximately 20˚C).
o A 250 mL beaker filled with 200 mL ice water (0˚C).
3. Obtain three test tubes and measure and place 1 gram of sodium polyacrylate
into each.
4. Obtain three Vernier Temperature Probes, three analog thermometers, and three
ring stands with clamps.
5. Start Logger Pro® software on the computers.
6. Click on File Open and open the Forensics with Vernier folder.
7. Open the program titled 14 Hot Air, Cold Body.
8. Connect the LabQuest Mini to each computer using USB cables.
9. Connect the Temperature Probes into CH 1 of the LabQuest Minis using the
British Telecom connector.
10. Place the thermometer in the water baths to ensure that they maintain the correct
temperatures. Record this temperature in the Evidence Record table.
11. Attach the Temperature Probes to the clamp on the ring stands.
12. Place 20 mL of 37˚ water into the test tubes. These represent dead bodies.
13. Place a test tube with waterlock representing the dead body in each of the three
water baths.
14. Place a Temperature Probe in the center of each test tube with waterlock.
15. Wait for the temperature sensors to reach the temperature of the waterlock. Click
to begin data collection. Note that the experiment is set to collect data for
20 minutes.
16. Make sure to maintain a constant temperature for your water baths throughout
data collection.
17. When data collection is complete (data has been collected for 20 minutes), click
the Statistics button,
, to display a Statistics box.
18. Record the minimum temperature recorded and the maximum temperature
recorded in the appropriate spot in the Evidence Record table for each water
bath.
19. Record the temperature change and record in the Evidence Record table for
each water bath. (Note: The temperature change is displayed in the Statistics
box as Δy.)
20. Copy the graphs by placing the mouse cursor over the graph, left clicking, and
then pressing both the Control and the C keys simultaneously. Paste the graphs
into a Word document and save. To paste the graph, press both the Control and
the V keys simultaneously. Repeat this step in order to copy and paste the Data
Table into the Word document. Attach the graphs in the Results section below.
21. Repeat the experiment for a total of three trials.
© 2013 Project Lead The Way, Inc.
Principles of Biomedical Science Activity 1.1.5 Time of Death Experimental Design – Page 3
McKenzie Doran
4. Carry out the experiment.
o Collect data.
o Make observations.
o Complete multiple trials. (Perform the procedure many times,
collecting data each time.)
Complete the data table. Include units and labels for each section.
Evidence Record
Assigned
Temperature:
Actual
Temperature
of Water Bath
Maximum
Temperature
of Waterlock
Minimum
Temperature
of Waterlock
Temperature
Change
(˚C):
(˚C):
(˚C):
Trial One
3.2˚C
29.1˚C
4.12˚C
24.98˚C
Trial Two
0.6˚C
30.1˚C
1.6˚C
28.5˚C
Trial Three
0.7˚C
32.2˚C
1.7˚C
30.5˚C
(˚C):
5. Analyze the data and observations.
o Make graphs or charts of the data.
o Check that the independent and dependent variables are properly
placed on any graphs.
o Be logical and clear.
o Look beyond the obvious.
Make graphs and charts to visually and logically present the data. Write in
paragraph form and include calculations showing all work. All analysis should be
explained clearly and concisely.
© 2013 Project Lead The Way, Inc.
Principles of Biomedical Science Activity 1.1.5 Time of Death Experimental Design – Page 4
McKenzie Doran
Graph:
Class Results:
Temp:
Group 1 Temp
Change
(˚C):
Group 2
Temp
Change
Group 3
Temp
Change
Group 4
Temp
Change
Group 5
Temp
Change
Average
Temp
Change
(˚C):
(˚C):
(˚C):
(˚C):
(˚C):
7.7˚C
12.5˚C
5.282˚C
50˚C
2.3˚C
5.94˚C
0.7˚C
Room
temperature
10˚C
6.7˚C
8.94˚C
27.99˚C
22.23˚C
(0˚C)
8.55˚C
25.11˚C
© 2013 Project Lead The Way, Inc.
Principles of Biomedical Science Activity 1.1.5 Time of Death Experimental Design – Page 5
McKenzie Doran
6. State the conclusion.
o Use a one sentence statement.
o Be clear and concise.
Write a one sentence statement directly related to the original hypothesis. It
might start with “The hypothesis was correct…”
Conclusion:
The hypothesis was correct in that the ambient temperature of a dead body does
change the rate of cooling.
7. Summary Paragraph
o Write a brief paragraph.
o Explain the rationale for your conclusion.
o Clarify details.
Write one paragraph of text explaining the rationale for the conclusion.
Summary Paragraph:
A dead body always wants to become the same temperature as the air
around it, so it tries to get there as fast as possible. This means that the rate of
cooling will change if the ambient temperature is lower or higher than the
temperature of the body. The change in the rate of cooling depends on how
drastic the difference between the body and air around it. Because of this, the
rate of cooling has to be considered in figuring out the time of death, and you will
use the Glaister equation to figure out time of death because it considers the
changes in rate of cooling.
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Principles of Biomedical Science Activity 1.1.5 Time of Death Experimental Design – Page 6