This material could be used to introduce empirical formulas, ionic bonding considerations, and stoichiometric relationships. Another possible focus is on the magnetic character of magnetite and an explanation of the spiking behavior of the ferrofluid. Explanations of magnetism hinge on electron configurations and thus to basic ideas from quantum mechanics. The surfactant employed provides an opportunity to discuss hydrophobic and hydrophyllic interactions. Ferrofluids make an important connection to nanotechnology, as the magnetic particles that are produced are typically on the order of 100 angstroms (10nm) in size. Particles in this range have a large surfaceto-volume ratio that can in some cases dramatically influence their properties. In this case, the particles have a characteristic response to a magnet that leads them to be described as superparamagnetic
Teacher Information and Instructions
Student Information and Instructions
Materials
- Magnetic stirrers and stir bars
- Cow magnets (0.5 in. x 3 in.), available from farm supply stores or from Edmund Scientific
- Strong magnet (neodymium-iron-boron), available from the physics department or Edmund Scientific
- 2.0 M FeCl2 in 2 M HCl
- 1.0 M FeCl3 in 2 M HCl
- 0.7 M NH3
- 25 % aqueous tetramethylammonium hydroxide solution, available from Aldich