Interactive video lessons, Figure 17, are used to replace up to half of the wet laboratory work for non-major general chemistry students (1). The computer lessons cover chemical reactions, chemical equations, solubility, euilibrium, oxidation and reduction, gases, acids and bases, reaction rates, orbitals and electrons, transition metals, heats of reaction and batteries.
This type of instruction extends the content of the course by allowing students to interact with video-based experiments which are difficult to do in traditional laboratories and which reduce student exposure to potentially hazardous materials or procedures. Students may repeat lessons as often as they want so time limited laboratory work becomes a competency based exercise.
Replacing actual laboratory experiments with computer simulations is controversial. Many people feel that students should have more lab experiments, not fewer. There are many factors which make it more likely that lab simulations will become increasingly important for non-chemistry majors. One of the most difficult issues is that of chemical waste disposal. When there are thousands of students the quantities of waste generated are considerable, even when microscale amounts are used. While most students are cooperative and understand the importance of proper separation of chemical waste, a small percentage don't do what they are asked. As as result, cross-contaminated waste is generated. There are also pressures to reduce the loads of teaching assistants, and to reduce the number of TAs we employ.
We have tried to design the lab schedule for first semester students so that they are exposed to a variety of lab experiments and can actually collect data, and have replaced experiments that the can be done better with the aid of computers. For example, the similation on Solubilities allows students to mix solutions, determine what solid, if any, forms, and to derive their own solubility rules. This experiment can not actually be performed in the lab because many of the metal ions are toxic. Both the lab experiments and computer simulations correspond to lecture material as much as is possible. In many cases, the computer simulations expand on the material covered in lecture, making it possible to include concepts it would not otherwise be possible to cover. Table 1 below shows the first semsester experiment schedule with alternating lab experiments and computer simulations.
|Week 1||Check-In||Drawer assignments, Safety lecture|
|Week 2||Lab Experiment||Properties of Common Substances--Household Chemicals|
|Week 3||Computer Simulation||Chemical Reactions--Writing Reactions and Balancing Equations|
|Week 4||Lab Experiment||Synthesis and Analysis of a Copper Sulfide--Stoichiometry|
|Week 5||Computer Simulation||Solubilities--Determining Solubility Rules by Experimentation|
|Week 6||Lab Experiment||Emission Spectroscopy--Determining Spectral Lines of Hydrogen|
|Week 7||Computer Simulation||Gases--Plotting Data and Finding the MW of an Unknown Gas|
|Week 8||Lab Experiment||Spectrophotometric Analysis--Synthesis and Analysis of a Cobalt Complex|
|Week 9||Computer Simulation||Equilibrium--Chromate-Dichromate Experiment|
|Week 10||Lab Experiment||Acid-Base Titration--Strong Acid-Strong Base Titration|
|Week 11||Computer Simulation||Acids and Bases--pH Unknown, Titration Experiment|
|Week 12||Lab Experiement||Buffers, Weak Acids and Weak Bases--Producing a Buffer|
|Week 13||Computer Simulation||Redox--Oxidation and Reduction, Balancing Redox Reactions|
Figure 17, Part of a lesson on solubility taken from Exploring Chemistry.