As I prepped my “into” for the “Titanic” story in our reader, I had an idea of how to demonstrate to my fourth graders the properties of icebergs. Specifically that nine-tenths of an iceberg is underwater. I had noted that my students knew very little about measurement – and I was dying to use the cool “ruler tool” on my new Activboard whiteboard.
Monday I handed out a plastic cup of water and an ice cube to each group. Next I had them measure the length and width of their ice cube (per my whiteboard demonstration). Then I had them drop their ice cube in the cup and measure how much of the cube was above water (am I good or what?).
Now, here is where you have to understand my thinking. You see, the ice cubes had only been out of the freezer for about 5 minutes, and they only needed to be in the water for about 30 seconds, and ice cubes in a drink last for minutes … so no problem. I did warn the students that they would have to measure quickly, so I wandered around watching students line their rulers up with the surface of the water – “to get a good accurate measurement.”
Not 20 seconds went by before the first defeatist comment was uttered. “Mr. Crosby, it’s hard to see to measure,” a quitter exclaimed. “I know, I know, but you can do it,” I encouraged (Plus, come on, I demo-ed this with the “ruler tool” on the Activboard – you can’t do better than that! … Can you?)
My first clue that there was a problem was when a student fished out a sliver of ice the size of a fingernail clipping and tried to measure it while he held it between his fingers – and it disappeared! The next clue was the group that exclaimed, “We can’t find our ice anymore!” as they scanned the iceberg free water in their cup. (Did I mention I used the “ruler tool” to demonstrate this?)
At this point I busted up. I busted up laughing because not only did I miscalculate how long the ice would last, but the kids were trying so hard to do a good job, and some seemed afraid they had done something wrong – the forlorn looks on their faces told the story.
Fortunately, I had several extra pieces of ice (Hey, I’m not a total screw up!) and we successfully measured one and used it as “The class measurement.” We did the math and came out with the fraction 2/20 which reduces to 1/10 of the cube that stuck above the surface – which is just what part of an iceberg floats above the surface of the water.
So, when the picture of the iceberg came up during the story, the kids were able to imagine how much was underwater.
Learning is messy!