*urgent 50 points* how to calculate the mass and volume of a plastic foam ball? (type out materials and apparatus as well)

Hmm...

Well the mass is as easy as weighing the ball.

The volume can be done in a couple of ways, the easiest of which is to fill a measuring jug with water and then submerge the ball, then simply measure how much the water was displaced for the volume. You would need to make sure the ball is totally submerged but not your finger or it will be inaccurate.

Mathematically you can use the following V = ⁴⁄₃πr³

π = pi
r = radius

To do this you would need a set of scales, a jug, some water, a pen, a ruler and some paper.