…all part of a ice house project investigation in math class.
Do all the bottles freeze at the same temperature?
As part of our Chewonki Ice House Project investigation, we were interested in the difference between pure water and salt water as the medium for cooling our food. So, we placed three 2-L plastic bottles containing pure water, 5% & 10% salt solutions on the Wallace Center porch on a very cold evening. Temperature probes were inserted into each bottle and one probe measured air temperature.
The results of our experiment were clear. All solutions started at 220F. The pure water froze at 00C, the 5% saline sol’n froze at -2.750C, and the 10% saline sol’n froze at -60C. The atmospheric temperature started at -100C and dipped to -160C during the night (It must have been pretty chilly in the cabins!). The pure water froze 2.5 hours into the test; the 5% saline sol’n froze 3.76 hours into the test: and the 10% saline sol’n froze 4.75 hours into the test. Here is a graph of the test:
Semester students who have done Polar Bear on Saturday mornings know that the saltwater at the waterfront freezes far later then the water in the farm pond. Here is some evidence that those Polar Bear dips have been VERY, VERY COLD!
Which 2-L bottle do you think will melt first when placed on the counter in the Flintstones?
The final question that we had was which frozen 2-L bottle (pure water/5% saline/10% saline) could cool 15-L of water the most? This question is very important since we need to choose the best medium to cool our food. We did the test, but we don’t want to spoil it for you. So what do you think? Which 2-L bottle was most effective at cooling the 15-L bucket of water?
Questions, experiment design and polar bears brought to by Steve Kerchner, Chewonki Math Teacher and MRPB (Most Reliable Polar Bear).