Exactly How Small is Small?

To the students;

Part of the work we do in chemistry is organizing data and presenting work in a logical order. This is especially important in a lab that is quantitative. We will be considering molecular size; small errors errors can make a big difference. Students need to think through their procedure, write it down and be ready to work for the next class to obtain meaningful results.

You can find the thickness of a rectangular sheet of aluminum foil from its length, width, and volume. To find its volume you will need its mass and the density of aluminum. What do you find its thickness to be?

Solid do not flatten into layers by themselves; they must br rolled or hammered. Liquids on the other hand tend to spread themselves into thin layers be themselves. In fact, some liquids spread into monomolecular layers. Such a substance is a 5% solution of Oleic Acid, which is in an alcohol solution. In order to see where it spreads, we will be use a tray of water with a THIN dusting of powder onto which we drop the solution. You will be using a single drop of solution for this activity for which you will need to find the volume. Be sure to include this method and data in your writeup. You will also need to know that the bases's length and width are each about 1 / 10 of its height.

What is the height of the molecule?
What is the number of moleclues in the layer?
If the density of oleic acid is 1 g/cc, what is the mass of one molecule of oleic acid? (remember the solution was only 5% oleic acid.)?



To the teachers;

This activity is used as I begin Chemistry as an introduction to laboratory situations and as the mathematics class is concurrently doing numerency, powers of ten etc. It is done outside on a nice day and helps students better understand just how small even large moleculescan be. It is also a good application to the review of density and how it will be used at a different level in Chemistry. The results of this activity are used as we develop molecular and atomic theories as well as the concept of the mole. Although it is a eirivation of the IPS lab on atoms, it is at a level even our better students are challenged to understand when formulas are not given.

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Last modified: May 30,1998