When I was in grade 11 my chemistry teacher had us do a case study called Avogadro Goes To Court to introduce our stoichiometry unit.  Stoichiometry is a fancy word for the study of reactants and products of a reaction.  It is founded on the law of conservation of mass.

Our mission was to determine the cost of a single atom of aluminum.

We were to make our measurements to three significant figures, and document our analysis in detail (with consistent units!).

Given Information

Avogadro’s Constant =
1 mol of aluminum has mass m =
The cost of the roll of aluminum foil =
The area of the roll listed on the box =

Procedure

1. Obtain a piece of aluminum foil.  Flatten it and measure the sides.  Mass it using a balance.  Record measurements to three significant figures and note the units.  (Note:  It’s always a good idea to convert to standard units as soon as possible!)
2. Calculate the amount of mols are contained in the rectangle using the measured mass and given molar mass.
3. Calculate the number of particles contained in the rectangle using Avogadro’s constant.
4. Determine the mass of the entire roll of aluminum foil.
5. Calculate the amount of mols contained in the entire roll of aluminum foil.
6. Calculate the number of atoms contained in the entire roll of aluminum foil.
7. Divide the price of the roll by the number of atoms in the roll.

Conclusion

One aluminum atom costs .

$3.40 was enough for eight million billion billion atoms!
(8 000 000 000 000 000 000 000 000 aluminum atoms in the roll.)

This was a great activity to get students comfortable working with extremely large numbers of particles.  It’s also great practice using unit analysis to ensure consistent results!

You can find the case study Avogadro Goes to Court from the National Centre for Case Study Teaching in Science at the University of Buffalo here.