Why empty aluminum cans don't have the mass pV predicts

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Bcisewski
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Please correct me if wrong, but to explain why the mass of the pile is not pV = (2700 kg/m3)(1.0 m3) = 2700 kg, is because a pile of empty cans, its volume would be more of a dimension vs a weight. please explain concept if someone can. Thank you

Question: A pile of empty aluminum cans has a volume of 1.0 m3. The density of aluminum is 2700 kg/m3. Explain why the mass of the pile is not "p(alumin)*V "= (2700 kg/m3)(1.0 m3) = 2700 kg. Used from the formula p=m/V
 
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The mass of some volume of stuff is [itex]m = \rho V[/itex], where [itex]\rho[/itex] is the density of whatever stuff fills the volume. Only if it were solid aluminum, would [itex]\rho[/itex] equal the density of aluminum. An empty can is mostly air, so the average density is much less than that of pure aluminum.
 
Thanks for the assistance, I overlooked the cans as having space within. I guess sometime the obvious to some may be difficult to see for others.