From: Paraluman Stice-Durkin (pstice-durkin@punahou.edu)
Date: Fri Jun 27 2003 - 13:01:44 PDT
Message-ID: <000601c33ce6$efc4c2a0$524e5e18@hawaii.rr.com> From: "Paraluman Stice-Durkin" <pstice-durkin@punahou.edu> Subject: significant figures Date: Fri, 27 Jun 2003 10:01:44 -1000
I use the phrase "a drop in the bucket" to demonstrate
significance/insignificance in adding numbers. I get a bucket of water (1
or larger) and several other measuring devices: graduated cylinders of
various sizes, down to a pipet or buret. Fill the bucket 3/4 full and have
students record that amount to the correct number of sig figs. Usually
there is some sort of crude measurements on the side. Discuss the
uncertainty. Then add different volumes to the bucket and record each
amount. The last to add should be just one drop, measured with your
smallest device (.1 ml if you use a buret). Then measure your new volume
using the bucket's scale. Should be the same or just a little different vs.
adding the numbers numerically on the board. Demonstrate how the
"insignificant" amount is not important in your answer if it is just "a drop
in the bucket".
A shorter demo would be to get a beaker of water, and record the volume
using the graduations (also why a graduated cylinder is a preferred device
for measuring volume). Then take a pipet and drop in 1 ml of water. The
new volume should be the same according the the beaker measurements. The
students see that relative to the rest of the sample, and the measuring
device available, the small amount is not significant.
aloha, paraluman
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