The density of styrofoam can vary depending on the type and the manufacturing process. However, a typical density for a styrofoam ball would be around 0.01 to 0.03 grams per cubic centimeter (g/cm³) .

Here's why it's hard to give a precise number:

* Different Types: There are many types of styrofoam, each with varying densities. Expanded polystyrene (EPS) is the most common type used for balls, and its density can vary.

* Manufacturing Process: The density of styrofoam depends on the size of the air pockets within the material. Different manufacturing techniques lead to different pocket sizes and therefore different densities.

Keep in mind that styrofoam is very lightweight due to its low density, making it ideal for things like insulation, packaging, and recreational items like balls.