One example of the buoyancy concept is the cola can experiment.If you take an aluminum can of cola and place it in a bucket of water,it will sink. However, if you pour out all the cola from the aluminum can and then place it a bucket of water, it will float. The combined effect of a filled cola can bring the density to a higher level, hence it sinks. Another experiment can be tried at home. Get some ice from the freezer and see if it floats. Normally,you would think that a block of ice would not float. After all, it is made from water. Will water float on water? But a block of ice will float since the density of frozen water is actually lower than when it's in liquid form.