Science Buddies: "Ask an Expert"

so i am doing my project on if the weight of someone affects how fast or slow your body heat goes down after a person is killed. i chose this project to see if you could see how long a person has been dead with the info of their weight and body temp. i am stuck though i dont know what i can test it on i cant test it on actual people so i need something to test it on and i cant figure it out. i was wondering if i could just do it on an orange or apple or something but im not sure if it would work the same. PLEASE HELP!!!!!

Very interesting project! I think you could perform tests on food items such as oranges, apples, potatoes, etc that you've heated to the same temperature. Apples or potatoes may work better than oranges because of the thick peel on an orange.

I think you should also consider testing for how the surface area of a person affects how fast or slow their body heat goes down. You could test pieces that are the same weight but cut in different ways so they have different surface areas.

Going back to your original question on murder victims, you may find that the weight and the surface area of a person may effect their rate of cooling. For example, an overweight 5'5" person may weight the same as a very skinny 6'3" person but they may not cool at the same rate because the 6'3" person has more surface area.

Audrey

Thank you so much, surface area isn't something I have thought about.

I thought Halloween was over? Just kidding.

The cooling rate is affected by numerous factors: total mass, mass to surface ratio, ambient temperature, wind, clothing, position, sunlight, bedding, fever, chills, etc. The medical examiners have a few charts to use when deciding how much time has passed, and they usually use a liver temperature as a starting poing. A phone call to your local medical examiner may be helpful, if you can get them to take you seriously.

To test your ideas, I would start with water melons, large and small. They come in various sizes, have a solid core, are water tight, and a thick skin.

For greater differences in temperature, put them in the refrigerator for 12 hours and then chart the rise to room temperature. You should see a non-linear rate, you decide the shape of the curve. Look for Newton Cooling Effect too.

Be careful to insert the thermometer to the same depth for all measurements.

Thanks so much that helps a lot. I know that there is a lot of factors that affect the rate of body cooling so i was just going to use the objects in the same room so the surrounding temperature, humitity and other factors stay the same for the tests. A watermelon sounds like a good idea thanks for all of your help.