Rate of cooling of a body to determine the approximate time of death-using cooling water data 6
Abstract
Introduction
(i) Explain why estimation of the time of death is important in a murder investigation. (4 marks)
(ii) Briefly explain how rates of cooling can be used to determine the approximate time of death. (4 marks)
Theory
(i) Explain whats cooling? (i.e. explain what causes a body to cool). (2 marks)
(ii) State and briefly explain the mechanisms of energy transfer. (4 marks)
(iii) Explain Newtons law of cooling: include relevant equation. (4 marks)
(iv) Show that the solution of Newtons law of cooling is an exponential function given by the expression: = 0e-kt where = difference in temperature between the body and the surrounding, 0 and k are constants to be determined. (6 marks)
Modelling
You are provided with experimental data to investigate the rate of cooling of a body.
I. Use the data to verify Newtons law of cooling and determine the cooling constant, k.
(i) Using excel, draw a graph of temperature against time (6 marks) and use your graph to determine the rates of cooling at four
different temperatures. (8 marks)
(ii) Enter your results in the table provided and determine the cooling constant. (4 marks)
II. Using excel, draw appropriate graphs to determine if the data can be represented by an exponential function. (12 marks)
Use your graphs to determine the values of 0 and k. (6 marks)
Compare the cooling constant, k with the value obtained from part (I). (2 marks)
-> find the percentage of difference
III. Discuss your results using appropriate scientific language.
Explain how the results of your investigation can be used by Forensic Scientists and the Police to estimate the time of death. (4 marks)
Conclusion and evaluation
(i) Discuss the main findings of the investigation. (4 marks)
(ii) Discuss the relevance/implication of your findings in a murder investigation. (2 marks)
(iii) Compare your results with literature. (4 marks)
(iv) Make an evaluation of the methods used/Discuss sources of error in your method used to
analyse the data. (4 marks)
(v) Make realistic suggestions how the investigation may be improved. (4 marks)
(vi) Suggest any further investigations that may be carried out. (2 marks)
