Does a 1ft round piece of iron weigh the same as a 1ft by 1ft by1ft deep square piece?

Answer 1

Of course not. Imagine putting that 1-foot wide ball of solid iron in a box that is exactly 1 foot square. Won't there be a lot of empty space all around the ball, except at the points where the ball touches the flat wall of the container?

The empty space proves the volume of the ball (sphere) is less than the volume of the cube. If the volume is less, and if both are made of the same thing, the sphere will weigh less.