Activity 1.1.5: Time of Death Experimental Design
1. Identify the Problem or Question
State the research problem or question in one sentence.
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. This will be in the form of a hypothesis.
This solution design or hypothesis should be based on previously obtained knowledge or research and should be supported by scientific evidence. Identify the independent and dependent variables.
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.
The independent variable is:
The dependent variable is:
3. Design the experiment to be used to test your hypothesis. Include a list of all materials used.
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. Clearly define how the data will be collected and recorded, including measurement units. Design a data table to use to record information.
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.
3 Computers with Logger Pro software
3 Vernier Temperature Probes
3 Ring stands with clamp
3 Test tubes
Sodium polyacrylate (also known as waterlock)
Hot water bath set to approximately 50˚C
Ice water bath
Room temperature water
1. Wear the appropriate personal protective equipment.
2. Create the following three water baths:
A 250 mL beaker filled with 200 mL of water on a hot plate set to medium heat that is approximately 50˚C. A 250 mL beaker filled with 200 mL of water at room temperature (approximately 20˚C). 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....