why does a flat peice of aluminum foil sink, but a ball of aluminum foil float?
When you ball it up you trap air and make the overall density of the foil/air system 1.0 gm/cm^3 (water's density)Then the less dense foil-air ball will floatIf you just put the tin (or aluminum) foil on the water without shaping it like a boat and thus containing no air, the more dense metal (compared to water) will sinkThat's why you can build cement boats if you are so inclinedBy trapping air using geometry, you can get the composite density of the material less than the density of water-Fred
