This was a fun little activity we did in Chapter 11: Geometry and Measurement Relationships, right after finishing Section 11.2: Surface Area of a Cylinder. A couple students had difficulty grasping how to calculate the lateral surface area of a cylinder. To investigate this concept, we* cut up a can of Coke, and showed them how the side turns into a rectangle. Most students have done nets before, using paper, and this allowed them to see it in another context. (* Okay, so I actually cut it up. I didn't really trust myself to do it without cutting myself, and I wouldn't have trusted 50 grade 8 students to do it without at least one injury.)
One advantage to this problem is that students get to see that in real life, answers are always approximate to some extent. Let's be honest, though: the main advantage to doing this activity with Coke is that students work harder when food is involved.
Download as PDF: Chapter 11 Activity- Surface Area and Volume of a Can of Coca-Cola
This is what the Coca-Cola can looked like after it was cut up. You can't tell from the photo, but it is sliced up the back. Upon reflection, I would definitely recommend using a box-cutting knife instead of scissors.
Here is the question I asked, as well as the beginning of the work that students put up afterwards.
And this is the end of the question. Instead of calculating the percentage of sugar in the can $latex (V \approx 398.16~cm^3)$, we calculated the percentage of sugar in the Coke itself $latex (V = 355~cm^3)$. It doesn't really make sense to calculate the percentage of sugar by volume for the entire can, since this would include the empty space.