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Finding number of atoms and volume

  1. Sep 15, 2012 #1
    1. The problem statement, all variables and given/known data

    The mass of a copper atom is 5.30 10-25 kg, and the density of copper is 8 920 kg/m3 .
    (a) Determine the number of atoms in 1 cm3 of copper.

    _______Cu—atom/cm3



    (b) Visualize the one cubic centimeter as formed by stacking up identical cubes, with one copper atom at the center of each. Determine the volume of each cube.


    _______cm3/Cu—atom




    (c) Find the edge dimension of each cube, which represents an estimate for the spacing between atoms.

    _________cm



    2. Relevant equations

    Density=mass/Volume



    3. The attempt at a solution


    Well, the book the book we are using for this class "Physics for Scientists and Engineers" by Serway has no right being used in an Introductory Physics class.

    I re-read the relevant chapter THREE times and still haven't figured out how to solve this.

    Therefore, I used my intuition alone.

    Using the info I have:

    3.06*10^(-25)kg= (8,920kg/m^3)*1cm^3 = M=D*V

    I cancelled the volumes but that won't left over any missing variables.

    I googled for alternatives and my textbook absolutely does not point us in any direction regarding this question. Please help.

    Thanks in advance.
     
  2. jcsd
  3. Sep 15, 2012 #2

    lewando

    User Avatar
    Gold Member

    You need the answer from a) to do b) and c). So focus on that first. It is essentially a unit conversion problem.
     
  4. Sep 16, 2012 #3
    Yes, I just figured that this morning. Thanks.

    But now I am having trouble with that.

    I equated:

    (8920kg/m^3)*(m/cm)*(cm-atom)/kg=Cu-atom/cm^3

    Then 8920/m^3*1m/100*5.24*10^(-27)=Cu-atom/cm^3

    But now what? Does my setup even look right?
     
  5. Sep 16, 2012 #4

    lewando

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    Gold Member

    Not really. You need to inventory all of your unitary conversion factors and apply them correctly.
    1 = 1 Cu atom / 5.30 10-25 kg
    1 = 1m3 / 1x106 cm3
    1 = 8920 kg / 1m3

    You are trying to convert 1 cm3 [of Cu] to Cu atoms. If you had a unitary conversion factor
    in the form of:
    1 = X Cu atoms / Y cm3 you would be close to being finished with part a). Can you try this using the above unitary factors?
     
    Last edited: Sep 16, 2012
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