A piece of copper wire has a density of 8.9g/cm cubed. What is the density of a chunk of copper that has a mass of 250 grams.?

Question

It's a question on my science homework about the periodic table.. And I can't figure it out. I don't know how to set the problem up Since there's only a mass. 

Answer 1

The density of copper should be the same in a wire as it is in a chunk,

so the answer is 8.9 g/cm³.

 

 

However, I'm assuming that this problem is really looking for the volume of the copper chunk.  

 

Think of density as a conversion factor that you can use to convert mass→volume or volume→mass.  

It's (8.9 g / 1 cm³) or (1 cm³ / 8.9 g).

 

To solve this problem, multiply 250 g by the latter.  It's the same as dividing the mass by the density, but that's really not important here.  As long as the units cancel out to a volume unit, everything's fine.  

 

250 g x (1 cm³ / 8.9 g) = 28 cm³

 

Note that the grams cancel here and all that's left is cm3, which is a volume unit.

Answer 2

Hi Sue,

 

Well, the density wouldn't change no matter how much or how little the mass of copper is. So if you have 250 grams of copper, it would also have a mass of 8.9 grams per cubic centimeter. If, however, you were looking for the volume of a chunk of copper that had a mass of 250 grams, you would simply divide mass by density, since that would give you volume:

 

250 grams divided by 8.9 g/cm^3 = 28 cubic centimeters.