I gave my honors chemistry 2 students a lab practicum for their mid-term exam yesterday. I assigned them in groups of three and gave them two problems to solve and write up (in a format similar to the one I require for lab notebooks) during the 90-minute exam:
- Find the molar mass of an unknown salt of an alkali plus a halogen by measuring the boiling point elevation.
- Determine the Celsius temperature of absolute zero by measuring the pressure of a sample of gas at different temperatures and extrapolating.
As has been the case for their other experiments during the year, they had to figure out the procedure on their own, perform the experiment, record the data, and perform the calculations.
Last year I gave a similar practicum exam to my CP1 (the level below honors) chem 2 students, except that it was a 2-hour exam and they had to perform three experiments. This time around, I was struck by a major difference: the honors kids spent a lot more time thinking their experiments through before starting. The CP1 kids had no trouble completing three experiments in two hours, but the honors kids, even with an additional five minutes per experiment, ran out of time.
