Density Columns

Density column


Usually I start out physical science with something kids love: fire. I think kids should have as much fun as possible as nothing is so amazing as fire – even in the lab. I’m not the only one to think this is a great idea, according to Gever Tulley’s TED talk. To fit something fun like fire into grade 9, I have begun with a unit titled “Heat” or, on the curriculum guide, “Introduction to Kinetic Theory.” Doesn’t “Fire” sound better?

Anyway, principles of conduction and insulation are fun, when they include fire, but are abstract and can be tough to learn. I use great, engaging materials from learning guru Ron Marson’s “TOP Science.” but abstract concepts are still at the horizon of many 9th graders abilities.

So this year I took a page from my principal’s science book, and decided to open the year with a unit in “Density.” Buoyancy is abstract but density is less so. We started by building paper shapes out of 1 cm cubes. Kids are given a 2D drawing of a 3D cubic shape projected on the screen. Then they cut a flat shape out of their 1 cm grid paper and fold it into the desired shape. First we build cubes of different volumes, then simple rectangular prisms (boxes) and then more complex shapes. 

At the conclusion of the unit I love to have students build a capstone construction. In this unit, I wanted them to build something that reflected an understanding of “density.” I came up with a “Density Column” whose specifications are listed here. Kids did a great job! A number earned full credit (100%) according to the rubric. And I love the objective grading: number of layers and number of buoyancies. 

In the image above the 4 fluids of different densities is clear. Many students used alcohol as the least dense and honey as the most dense. It was popular too to use a battery or a stone as a solid object denser than the densest fluid and to use styrofoam or a ping-pong ball as the least dense. What I liked in the image at top was there a solid object (a wooden chess pawn) which has a density making it “float” inside the golden layer above the bottom-most layer.

I think “making stuff” teaches the maker many things and is intrinsically motivating, learning activity.


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