Writing Lab Report
Learning Goal: I’m working on a chemistry project and need a sample draft to help me learn.
You are asked to experimentally calculate Avogadro’s number. In order to do this, you will be analyzing a sample of copper wire. You mass a piece of pure, lab grade copper and learn that it has a mass of 1.08g. We can use the known physical properties of copper to determine Avogadro’s number. We CANNOT use the value of Avogadro’s number in the calculations.
Copper has a density of 8.96 g/cm3. This is tabulated and just ~known~. We can use the density and the mass to determine the volume (hint: you will need to show this calculation)
The volume of one copper atom can be found by assuming the atom is a sphere and finding the volume of the sphere with the radius of the atomic radius of copper. The atomic radius of copper is 1.96 Angstroms. (We will assume unbonded and free.<= SEE THIS… an assumption!) An Angstrom is 10-10m; a very small unit of length.
First, convert Angstroms to cm so that the calculated volume units of the sheet of copper will match the volume units of an atom of copper.
Use this radius as the radius of a sphere to find the volume of 1 atom of copper.
volume of 1 copper atom = 4/3 pi r3 = ??? cm3 / 1 atom Cu
Find the number of copper atoms in the copper wire by using dimensional analysis:
(volume from density cm3 / 1 piece Cu ) * (1 atom Cu / volume of 1 Cu atom cm3) = # atoms Cu in the wire
Find the number of moles of copper in the wire by using the molar mass found on the periodic table.
mass g Cu * 1mole Cumolar mass from periodic table g Cu= ?? mol Cu
Find the experimental Avogadro’s Number knowing that this number represents particles per mole.
# atoms Cu/ ?? mol Cu = Experimental Avogadro’s number
You can see that there is error in this experimental measurement. That error is largely due to the actual radius of copper while it is in a metal bonded wire. It isn’t a covalent bond nor is it free; it has metallic bonds. A metallic bond is a little different than a covalent bond and it distorts the atomic radius so that it deviates from the free atom.
To determine your percent error take the absolute value of the difference between the experimental and theoretical, divide by theoretical and multiply by 100.
% error = 100 * |experimental Avogadro – theoretical Avogadro| / theoretical Avogadro
Here Are the questions that I want you to answer
1-The procedure for this lab is fairly straight forward. Mass a sample of pure copper. Perform calculations. How would you write that in 3rd person passive objective voice?
2-Display the results of this lab by creating a table. Label the table and be sure your numbers have correct units.
3-Here is the big section. Write up an explanation of the calculations that need to be performed and display those calculations. Explain what each product of the calculation means. Lead me through the process.
4-Write 2-3 sentences that conclude the findings from this lab.
5-In the lab report, the Abstract comes directly after the Title. For this exercise, I want to emphasize that the abstract should be written last.
The abstract should contain:
1.1 sentence introduction to what was studied.
2.1-2 sentences summarizing the procedure
3.1-2 sentences with results
4.1 sentence conclusion
5.1 sentence offering what could skew the data.