Primary Unit Science The Philadelphia School Float your boat : At many schools, primary science instruction is based on learning and repeating poorly understood facts. We prefer to show children some intrinsically bizarre phenomenon, let them play with it, saying as little theory as possible, and ask for their ideas. Then we try to connect to other phenomena. We studied various examples of buoyancy, for example making Cartesian divers. The goal was to stay with phenomena close to everyday experience. Above: we show that soap bubbles will bounce off an invisible layer of carbon dioxide at the bottom of a bucket. Right: A can of regular soda sinks in water, but a can of diet soda floats. We make the can of regular soda float by dissolving a whole lot of salt in the surrounding water.