What can you do when kids don't get it?
In an effort to help my students grasp the concept, I started doing this significant digit lab each year. The materials list is super simple: a wood block, three different balances, and three different rulers. Students begin by measuring the length, width and height of their wood block using a diagram of three different rulers.
They are frustrated by the first ruler. They don't like having to estimate! I quickly get the students to understand that the first ruler has only one significant digit, the second ruler has two, and the third ruler has 3. They use the measured length, width, and height to determine the volume.
Next students get the mass of their wood block using three different balances.
Now that the volume and the mass is known, students must calculate the density of the wood block to one significant digit, two significant digits, and three significant digits. We then calculate the percent error, using our three-significant-digit density as the true value. Wow! Kids quickly realize how important significant digits are to a measurement.
Throw in an additional page of practice problems on rounding and calculating with significant digits, and I'll call this day a success! I hope you are off to a great school year. I'd love to hear your ideas on significant digits!