Polystyrene and Styrofoam

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1. The problem statement, all variables and given/known data
Devise and preform an experiment to determine what fraction of the volume of a sample of Styrofoam is air. We know that Styrofoam is made of Polystyrene with air bubbles. The mass is the same, the volume is different.


2. Relevant equations
Mass/Volume=Density


3. The attempt at a solution

Well I thought that If I find the density of both the samples (Polystyrene and the Styrofoam) and find the difference and divide it by the density of the Polystyrene I could find the fraction of air, but I'm not very sure.