Grapefruits and Maps

My 7th grade is studying map projections, learning about how and why it is hard to make an accurate map and the influences on cartographers that affect the maps that they make. I read online at Education World about an activity that used grapefruits to help students learn the challenges involved. It sounded like fun, messy but fun. I reserved the cafeteria to make sure that the students could relax and not worry about the mess and to make sure that there would be lots of paper towels and cleaning solution available.

The first challenge turned out to be the grapefruits themselves. I had completely forgotten about the weather issues this summer that had impacted the grapefruits crops. It was only as I was standing in the market at 7:00 AM, seeing no grapefruits in sight, that I remembered. Luckily, with some searching, I found a small display of very expensive fruit. Given the fact that this was my lesson and I really wanted to try it, I bought half the number that I had originally planned on, deciding that the students could work in pairs rather than independently. Then I collected the necessary plastic knives and permanent markers, and I was ready to go.

We started class in my classroom. I gave each pair a grapefruit and a marker. They loved it before it even began.

“What are these for?”

“Do we get to eat them?”

“Is it snack?”

Food is such an easy hook! I instructed them to have one girl find the top of the grapefruit and label it either the North or the South Pole. We had looked at some of those wonderful maps projections that have the South Pole at the top of the world, so I wanted to let them make a decision as to which way they were going to orient their “globe.”

http://en.wikipedia.org/wiki/File:Blank-map-world-south-up.png

I then had the other partner draw on the equator, halfway between the poles. They then took turns adding the most basic outlines of the continents. Permanent markers do not work all that well on grapefruit rinds, but they were what I had, so I just kept encouraging them to make it work the best that they could.

I posed the question to them, “How can you turn this globe that you have made into a 2-dimensional map?” I challenged them to talk with their partner about the strategy they would use as we walked to the cafeteria. It was a noisy and energetic walk, filling the halls with eager suggestions and conversation, as they discussed how to get the grapefruit pealed.

It was messy and wonderfully fun, as they tried to figure out how to create a map that made sense. Some of them simply peeled on small pieces and the placed them close together, usually with some unknown parts left to cause confusion. Others cut the grapefruit in half and worked on figuring out a strategy to get it to lie flat on the table.

Once they had created a “map” with their grapefruit rinds, then I had them draw their map on a large piece of paper, labeling as much as they could. Unfortunately, grapefruit juices and lots of pushing and manipulating of the rinds caused a lot of the marker to wash off, but all of them were able to identify the equator and some of their continents.

When they were all done, we had a massive Clean-Up of the cafeteria tables, scrubbing them down and composting the leftover grapefruit – the parts that hadn’t been eaten during the exercise.

Back in the classroom, I asked what they had learned about the process of making maps and about being cartographers. The first and strongest response was:

“It’s hard!”

They understood that the decisions that each partnership made in the beginning impacted the map that they created. Their choices and ideas truly have an effect on the map that was made. Lesson achieved!

I doubt they will ever look at a map the same way again!