Science Buddies: "Ask an Expert"

Hi, my 5th grade son is working on his science project with insulation.
His Question is: Which type of insulation (cotton, wool, or fat) slows down the heat loss compared to no insulation? We divided a shoe box in 4 equal parts, and placed a canning jar into each space. We filled gaps in each sapce with those insulation materials with one gap left unfilled (no insulation) . We poured tap water into the jars and place lids on them, and stored the whole box in a freezer. recorded water temperature every 20 mins for 100 minutes.

The result is:
the temperature in a jar with no insulation went down steadily and reached 32F after 80min. Other three went down slowly and reached 50F after 80 min, but the way the temperature went down in those three jars were almost same, no much difference at all. When my son made a line graph to show how the temperture went down , those three line are almost one thick line. We were expecting to see wool keeping heat better that cotton, and possibly lard ( as fat) is the best material to keep you warm. But, They were all same. We are very disppointed to see no difference.

We are wondering if our procedure was not good. Could you tell us please what went wrong in our project? We would really appreciate that. We would like to conclude this project suggesting what we could have done to see more reasonable results.

Thank you very much!

mamanachan45,

Welcome to the forum and thank you for your question.

Results in science are not always as expected, which is the point. It may be that the materials you chose have very similar insulating properties. However, one must really monitor the control variables.

I'm assuming, but verify:
1) The size and shape of the jars were the same. The glass of the jar itself provides some insulation to the water inside, you have to ensure it is the same for all test subjects.
2) Ensure the amount (weight) of water in each jar is exactly the same.
3) Ensure the starting temp of water in each jar is exactly the same (say from 100 deg C).
It sounds like you probably did all of that...now also:
4) Ensure the "thickness" of the insulation material around each jar is the same on all side (including the bottom and top) for all samples. For example ensure 1 cm thickness of wool around jar 1, 1 cm of cotton around jar 2, and 1 cm of lard around jar 3, and of course control left without insulation.

I could see that the heat loss from each insulated case was probably slightly different from each other, and obviously quite different from the uninsulated control, but the result may be masked by the heat loss out the top and bottom, which from your description, sounds like they were left uninsulated. Also, between insulated jar sections, you have double insulation of different materials.

I would re-run the experiment by completely encasing each jar in insulating material and placing them separately in the freezer vs in the same box where the surface area exposed to the cold could be just different enough to skew results. I would even run the test on each case individually so that each test subject could be placed in the exact same spot in the freezer, eliminating the possibility of one test subject to be in a slightly "cooler" or "warmer" part of the freezeer. Also, i'd repeat at least 3 times to verify results and get an "average" insulating index factor for each test material.

This helps me a lot, to make a successful project you need to be careful and you should have a procedure to follow. I did my project about thermal insulation and I did it successful with the help of the researching procedure in the internet.

Hikari11,

I'm glad you found this useful. You are right. Science is 99% planning and research.