Why does changing the the shape of an object have no effect on the density of that object?

1 I'm not sure that this is true-- at least without some qualifications. If an object's shape is changed in such a way that it will enclose one or more pockets of air, some other substance, or even vacuum, the object's over-all density may change. If no pockets are formed, then the density probably is not changed

2 Density is the ratio of mass to volume.